def expression():
"""
Parses
expression = simpleExpression
{("=" | "<>" | "<" | "<=" | ">" | ">=") simpleExpression}.
Generates code for the expression if no error is reported
"""
x = simpleExpression()
while SC.sym in {EQ, NE, LT, LE, GT, GE}:
op = SC.sym; getSym(); y = simpleExpression() # x op y
if x.tp == Int == y.tp:
#============== ADDED CONSTANT FOLDING =============
if type(x) == Const == type(y): #
if op == EQ and x.val != y.val: #
x = genSkip() #
elif op == NE and x.val == y.val: #
x = genSkip() #
elif op == LT and x.val >= y.val: #
x = genSkip() #
elif op == LE and x.val > y.val: #
x = genSkip() #
elif op == GT and x.val <= y.val: #
x = genSkip() #
elif op == GE and x.val < y.val: #
x = genSkip() #
else:
x = genRelation(op, x, y)
else: mark('bad type')
def find(name):
for l in symTab:
for e in l:
if name == e.name: return e
mark('undefined identifier ' + name)
undef = Var(Int); undef.lev, undef.adr = 0, 0
return undef
def genVar(x):
# assuming x is ST.Var, ST.Ref, ST.Const
# for ST.Const: no code, x.val is constant
# for ST.Var: x.reg is FP for local, 0 for global vars,
# x.adr is relative or absolute address
# for ST.Ref: address is loaded into register
# returns ST.Var, ST.Const
if type(x) == Const:
y = x
else:
if x.lev == 0:
s = R0
elif x.lev == curlev:
s = FP
else:
mark("level!")
s = R0
y = Var(x.tp)
y.lev = x.lev
if type(x) == Ref: # reference is loaded into register
r = obtainReg()
putM("lw", r, s, x.adr)
y.reg, y.adr = r, 0
elif type(x) == Var:
y.reg, y.adr = s, x.adr
else:
y = x # error, pass dummy item
return y
def factor():
"""
Parses
factor = ident selector | integer | "(" expression ")" | "not" factor.
Generates code for the factor if no error is reported
"""
if SC.sym not in FIRSTFACTOR:
mark("factor expected"); getSym()
while SC.sym not in FIRSTFACTOR | STRONGSYMS | FOLLOWFACTOR:
getSym()
if SC.sym == IDENT:
x = find(SC.val)
if type(x) in {Var, Ref}: x = genVar(x)
elif type(x) == Const: x = Const(x.tp, x.val); x = genConst(x)
else: mark('variable or constant expected')
getSym(); x = selector(x)
elif SC.sym == NUMBER:
x = Const(Int, SC.val); x = genConst(x); getSym()
elif SC.sym == LPAREN:
getSym(); x = expression()
if SC.sym == RPAREN: getSym()
else: mark(") expected")
elif SC.sym == NOT:
getSym(); x = factor()
if x.tp != Bool: mark('not boolean')
elif type(x) == Const: x.val = 1 - x.val # constant folding
else: x = genUnaryOp(NOT, x)
else:
mark("factor expected"); x = None
return x
def simpleExpression():
"""
Parses
simpleExpression = ["+" | "-"] term {("+" | "-" | "or") term}.
Generates code for the simpleExpression if no error is reported
"""
if SC.sym == PLUS:
getSym(); x = term()
elif SC.sym == MINUS:
getSym(); x = term()
if x.tp != Int: mark('bad type')
elif type(x) == Const: x.val = - x.val # constant folding
else: x = genUnaryOp(MINUS, x)
else: x = term()
while SC.sym in {PLUS, MINUS, OR}:
op = SC.sym; getSym()
if op == OR and type(x) != Const: x = genUnaryOp(OR, x)
y = term() # x op y
if x.tp == Int == y.tp and op in {PLUS, MINUS}:
if type(x) == Const == type(y): # constant folding
if op == PLUS: x.val = x.val + y.val
elif op == MINUS: x.val = x.val - y.val
else: x = genBinaryOp(op, x, y)
elif x.tp == Bool == y.tp and op == OR:
if type(x) == Const: # constant folding
if not x.val: x = y # if x is false, take y, else x
else: x = genBinaryOp(OR, x, y)
else: mark('bad type')
return x
def compileFile(srcfn):
if srcfn.endswith(".p"):
with open(srcfn, "r") as f:
src = f.read()
dstfn = srcfn[:-2] + ".s"
compileString(src, dstfn)
else:
mark("'.p' file extension expected")
def simpleExpression():
"""
Parses
simpleExpression = ["+" | "-"] term {("+" | "-" | "or") term}.
Generates code for the simpleExpression if no error is reported
"""
if SC.sym == PLUS:
getSym()
x = term()
elif SC.sym == MINUS:
getSym()
x = term()
if x.tp != Int:
mark("bad type")
elif type(x) == Const:
x.val = -x.val # constant folding
else:
x = genUnaryOp(MINUS, x)
else:
x = term()
while SC.sym in {PLUS, MINUS, OR}:
op = SC.sym
getSym()
if op == OR and type(x) != Const:
x = genUnaryOp(OR, x) # -----
y = term() # x op y
if x.tp == Int == y.tp and op in {PLUS, MINUS}: # if (type(x)=int and type(y)=int) and (operator is + or -)
if type(x) == Const == type(y): # constant folding
## does x + y if they are not zero
if op == PLUS:
x.val = x.val + y.val
elif op == MINUS:
x.val = x.val - y.val
else:
print("op", op)
print("1. simpleExpression")
if type(x).__name__ == "Const" and x.val == 0:
x = y
print("x = y")
continue
elif type(y).__name__ == "Const" and y.val == 0:
print("x = x")
x = x
continue
x = genBinaryOp(op, x, y) # does the arithmetic + and minus
elif x.tp == Bool == y.tp and op == OR: # no changes past here
if type(x) == Const: # constant folding
if not x.val:
x = y # if x is false, take y, else x
else:
x = genBinaryOp(OR, x, y)
else:
mark("bad type")
writeln("TEST: ", "SimpleExpression: ", "5. ", "ended")
# print("--- x: ", dir(x));
print("function ending x: ", vars(x))
return x
def genFormalParams(sc):
"""For list sc with formal procedure parameters, determine the $fp-relative
address of each parameters; each parameter must be type integer, boolean
or must be a reference parameter"""
s = 0 # parameter block size
for p in reversed(sc):
if p.tp == Int or p.tp == Bool or type(p) == Ref:
p.adr, s = s, s + 4
else: mark('no structured value parameters')
return s
def genActualPara(ap, fp, n):
"""Pass parameter, ap is actual parameter, fp is the formal parameter,
either Ref or Var, n is the parameter number"""
if type(fp) == Ref: # reference parameter, assume p is Var
if ap.adr != 0: # load address in register
r = obtainReg(); putM('la', r, ap.reg, ap.adr)
else: r = ap.reg # address already in register
putM('sw', r, SP, - 4 * (n + 1)); releaseReg(r)
else: # value parameter
if type(ap) != Cond:
if type(ap) != Reg: ap = loadItem(ap)
putM('sw', ap.reg, SP, - 4 * (n + 1)); releaseReg(ap.reg)
else: mark('unsupported parameter type')
def expression():
"""
Parses
expression = simpleExpression
{("=" | "<>" | "<" | "<=" | ">" | ">=") simpleExpression}.
Generates code for the expression if no error is reported
"""
x = simpleExpression()
while SC.sym in {EQ, NE, LT, LE, GT, GE}:
op = SC.sym
getSym()
y = simpleExpression() # x op y
if x.tp == Int == y.tp:
x = genRelation(op, x, y)
else:
mark("bad type")
return x
def typedIds(kind):
"""
Parses
typedIds = ident {"," ident} ":" type.
Updates current scope of symbol table
Assumes kind is Var or Ref and applies it to all identifiers
Reports an error if an identifier is already defined in the current scope
"""
tid = [SC.val]; getSym()
while SC.sym == COMMA:
getSym()
if SC.sym == IDENT: tid.append(SC.val); getSym()
else: mark('identifier expected')
if SC.sym == COLON:
getSym(); tp = typ().tp
for i in tid: newObj(i, kind(tp))
else: mark("':' expected")
def program():
"""
Parses
program = "program" ident ";" declarations compoundStatement.
Generates code if no error is reported
"""
newObj("boolean", Type(Bool))
Bool.size = 4
newObj("integer", Type(Int))
Int.size = 4
newObj("true", Const(Bool, 1))
newObj("false", Const(Bool, 0))
newObj("read", StdProc([Ref(Int)]))
newObj("write", StdProc([Var(Int)]))
newObj("writeln", StdProc([]))
progStart()
if SC.sym == PROGRAM:
getSym()
else:
mark("'program' expected")
ident = SC.val
if SC.sym == IDENT:
getSym()
else:
mark("program name expected")
if SC.sym == SEMICOLON:
getSym()
else:
mark("; expected")
declarations(genGlobalVars)
progEntry(ident)
x = compoundStatement()
return progExit(x)
def term():
"""
Parses
term = factor {("*" | "div" | "mod" | "and") factor}.
Generates code for the term if no error is reported
"""
x = factor()
while SC.sym in {TIMES, DIV, MOD, AND}:
op = SC.sym
getSym()
if op == AND and type(x) != Const:
x = genUnaryOp(AND, x)
y = factor() # x op y
if x.tp == Int == y.tp and op in {TIMES, DIV, MOD}:
if type(x) == Const == type(y): # constant folding
if op == TIMES:
x.val = x.val * y.val
elif op == DIV:
x.val = x.val // y.val
elif op == MOD:
x.val = x.val % y.val
else:
print("term 2: start optimization op", op)
if type(x).__name__ == "Const" and x.val == 1: # check if x=1 for multiplications
print("x == 1, do not multiply by 1")
x = y
elif type(y).__name__ == "Const" and y.val == 1: # check for imediate for multiplications
print("y == 1, do not multiply by 1")
x = x
else:
x = genBinaryOp(op, x, y)
elif x.tp == Bool == y.tp and op == AND:
if type(x) == Const: # constant folding
if x.val:
x = y # if x is true, take y, else x
else:
x = genBinaryOp(AND, x, y)
else:
mark("bad type")
return x
def factor():
"""
Parses
factor = ident «write(ident)» selector |
integer «write(integer)» |
"(" «write('(')» expression ")" «write(')')» |
"not" «write('not ') factor.
Generates code for the factor if no error is reported
"""
if SC.sym not in FIRSTFACTOR:
mark("expression expected")
getSym()
while SC.sym not in FIRSTFACTOR | STRONGSYMS | FOLLOWFACTOR:
getSym()
if SC.sym == IDENT:
x = find(SC.val)
if type(x) in {Var, Ref}: x = CG.genVar(x)
elif type(x) == Const:
x = Const(x.tp, x.val)
x = CG.genConst(x)
else:
mark('expression expected')
write(SC.val)
getSym()
x = selector(x)
elif SC.sym == NUMBER:
x = Const(Int, SC.val)
x = CG.genConst(x)
write(str(SC.val))
getSym()
elif SC.sym == LPAREN:
write('(')
getSym()
x = expression()
if SC.sym == RPAREN:
write(')')
getSym()
else:
mark(") expected")
elif SC.sym == NOT:
write('not ')
getSym()
x = factor()
if x.tp != Bool: mark('not boolean')
elif type(x) == Const: x.val = 1 - x.val # constant folding
else: x = CG.genUnaryOp(NOT, x)
else: x = Const(None, 0)
return x
def simpleExpression():
"""
Parses
simpleExpression = ["+" «write(' + ')» | "-" «write(' - ')»] term {("+" «write(' + ')» | "-" «write(' - ')» | "or" «write(' or ')») term}.
Generates code for the simpleExpression if no error is reported
"""
if SC.sym == PLUS:
write(' + ')
getSym()
x = term()
elif SC.sym == MINUS:
write(' - ')
getSym()
x = term()
if x.tp != Int: mark('bad type')
elif type(x) == Const: x.val = -x.val # constant folding
else: x = CG.genUnaryOp(MINUS, x)
else: x = term()
while SC.sym in {PLUS, MINUS, OR}:
op = SC.sym
getSym()
if op == OR and type(x) != Const:
write(' or ')
x = CG.genUnaryOp(OR, x)
if op == PLUS: write(' + ')
if op == MINUS: write(' - ')
y = term() # x op y
if x.tp == Int == y.tp and op in {PLUS, MINUS}:
if type(x) == Const == type(y): # constant folding
if op == PLUS: x.val = x.val + y.val
elif op == MINUS: x.val = x.val - y.val
else: x = CG.genBinaryOp(op, x, y)
elif x.tp == Bool == y.tp and op == OR:
if type(x) == Const: # constant folding
if not x.val: x = y # if x is false, take y, else x
else: x = CG.genBinaryOp(OR, x, y)
else: mark('bad type')
return x
def expression():
"""
Parses
expression = simpleExpression
{("=" «write(' = ')» | "<>" «write(' <> ')» | "<" «write(' < ')» | "<=" «write(' <= ')» | ">" «write(' > ')» | ">=" «write(' >= ')») simpleExpression}.
Generates code for the expression if no error is reported
"""
x = simpleExpression()
while SC.sym in {EQ, NE, LT, LE, GT, GE}:
op = SC.sym
if op == EQ: write(' = ')
elif op == NE: write(' <> ')
elif op == LT: write(' < ')
elif op == LE: write(' <= ')
elif op == GT: write(' > ')
elif op == GE: write(' >= ')
getSym()
y = simpleExpression() # x op y
if x.tp == Int == y.tp:
x = CG.genRelation(op, x, y)
else:
mark('bad type')
return x
def body(ident, para):
if SC.sym == INDENT: getSym()
else: mark('indent expected')
start = len(topScope())
local = declarations(CG.genLocalVars)
CG.genProcEntry(ident, para, local)
if SC.sym in FIRSTSTATEMENT: x = statementBlock()
elif SC.sym == INDENT:
getSym(); x = statementBlock()
if SC.sym == DEDENT: getSym()
else: mark('dedent or new line expected')
else: mark('statement expected')
CG.genProcExit(x, para, local)
if SC.sym == DEDENT: getSym()
else: mark('dedent or new line expected')
return x
def term():
"""
Parses
term = factor {("*" | "div" | "mod" | "and") factor}.
Generates code for the term if no error is reported
"""
x = factor()
while SC.sym in {TIMES, DIV, MOD, AND}:
op = SC.sym; getSym();
if op == AND and type(x) != Const: x = genUnaryOp(AND, x)
y = factor() # x op y
if x.tp == Int == y.tp and op in {TIMES, DIV, MOD}:
if type(x) == Const == type(y): # constant folding
if op == TIMES: x.val = x.val * y.val
elif op == DIV: x.val = x.val // y.val
elif op == MOD: x.val = x.val % y.val
else: x = genBinaryOp(op, x, y)
elif x.tp == Bool == y.tp and op == AND:
if type(x) == Const: # constant folding
if x.val: x = y # if x is true, take y, else x
else: x = genBinaryOp(AND, x, y)
else: mark('bad type')
return x
def typedIds(kind):
"""
Parses
typedIds = ident {"," ident} ":" type.
Updates current scope of symbol table
Assumes kind is Var or Ref and applies it to all identifiers
Reports an error if an identifier is already defined in the current scope
"""
tid = [SC.val]
getSym()
while SC.sym == COMMA:
getSym()
if SC.sym == IDENT:
tid.append(SC.val)
getSym()
else:
mark('identifier expected', 48)
if SC.sym == COLON:
getSym()
tp = typ().tp
for i in tid:
newObj(i, kind(tp))
else:
mark("':' expected", 49)
def compoundStatement():
if SC.sym == BEGIN: getSym()
else: mark("'begin' expected")
x = statement()
while SC.sym == SEMICOLON or SC.sym in FIRSTSTATEMENT:
if SC.sym == SEMICOLON: getSym()
else: mark("; missing")
y = statement()
x = CG.genSeq(x, y)
if SC.sym == END: getSym()
else: mark("'end' expected")
return x
def program():
"""
Parses
program = "program" «write('program ')» ident «write(ident)»
";" «write(';')» declarations compoundStatement(1).
Generates code if no error is reported
"""
newObj('boolean', Type(Bool))
Bool.size = 4
newObj('integer', Type(Int))
Int.size = 4
newObj('true', Const(Bool, 1))
newObj('false', Const(Bool, 0))
newObj('read', StdProc([Ref(Int)]))
newObj('write', StdProc([Var(Int)]))
newObj('writeln', StdProc([]))
CG.progStart()
if SC.sym == PROGRAM:
#
write('program ')
writeHtml('program ')
#
getSym()
else:
mark("'program' expected")
ident = SC.val
if SC.sym == IDENT:
#
write(ident)
writeHtml(ident, _class='ident')
#
getSym()
else:
mark('program name expected')
if SC.sym == SEMICOLON:
getSym()
#
write(';')
writeln()
writeHtml(';')
writeHtmlLn()
#
else:
mark('; expected')
declarations(CG.genGlobalVars)
CG.progEntry(ident)
x = compoundStatement(1)
return CG.progExit(x)
def compoundStatement():
"""
Parses
compoundStatement = "begin" statement {";" statement} "end"
Generates code for the compoundStatement if no error is reported
"""
if SC.sym == BEGIN: getSym()
else: mark("'begin' expected")
x = statement()
while SC.sym == SEMICOLON or SC.sym in FIRSTSTATEMENT:
if SC.sym == SEMICOLON: getSym()
else: mark("; missing")
y = statement(); x = genSeq(x, y)
if SC.sym == END: getSym()
else: mark("'end' expected")
return x
def compoundStatement():
"""
Parses
compoundStatement = "begin" statement {";" statement} "end"
Generates code for the compoundStatement if no error is reported
"""
if SC.sym == BEGIN: getSym()
else: mark("'begin' expected", 17)
x = statement()
while SC.sym == SEMICOLON or SC.sym in FIRSTSTATEMENT:
if SC.sym == SEMICOLON: getSym()
else: mark("; missing", 18)
y = statement()
x = genSeq(x, y)
if SC.sym == END: getSym()
else: mark("'end' expected", 19)
return x
def compoundStatement(l):
"""
Parses
compoundStatement(l) =
"begin" «writeln; write(l * indent + 'begin')»
statement(l + 1) {";" «write(';')» statement(l + 1)}
"end" «writeln; write(l * ident + 'end')»
Generates code for the compoundStatement if no error is reported
"""
if SC.sym == BEGIN:
writeln()
write(l * indent + 'begin')
writeHtmlLn()
writeHtml(l * htmlIndent + 'begin')
getSym()
else:
mark("'begin' expected")
x = statement(l + 1)
while SC.sym == SEMICOLON or SC.sym in FIRSTSTATEMENT:
if SC.sym == SEMICOLON:
write(';')
getSym()
writeHtml(';')
else:
mark("; missing")
y = statement(l + 1)
x = CG.genSeq(x, y)
if SC.sym == END:
writeln()
write(l * indent)
write('end')
writeln()
writeHtmlLn()
writeHtml(l * htmlIndent)
writeHtml('end')
writeHtmlLn()
getSym()
else:
mark("'end' expected")
return x
def program():
newDecl('boolean', Type(CG.genBool(Bool)))
newDecl('integer', Type(CG.genInt(Int)))
newDecl('true', Const(Bool, 1))
newDecl('false', Const(Bool, 0))
newDecl('read', StdProc([Ref(Int)]))
newDecl('write', StdProc([Var(Int)]))
newDecl('writeln', StdProc([]))
CG.genProgStart()
if SC.sym == PROGRAM: getSym()
else: mark("'program' expected")
ident = SC.val
if SC.sym == IDENT: getSym()
else: mark('program name expected')
if SC.sym == SEMICOLON: getSym()
else: mark('; expected')
declarations(CG.genGlobalVars)
CG.genProgEntry(ident)
x = compoundStatement()
return CG.genProgExit(x)
def typedIds(kind):
"""
Parses
typedIds = ident {"," ident} ":" type.
Updates current scope of symbol table
Assumes kind is Var or Ref and applies it to all identifiers
Reports an error if an identifier is already defined in the current scope
"""
if SC.sym == IDENT:
tid = [SC.val]
getSym()
else:
mark("identifier expected")
tid = []
while SC.sym == COMMA:
# attribute
write(', ')
writeHtml(', ')
#
getSym()
if SC.sym == IDENT:
# attribute
write(SC.val)
writeHtml(SC.val)
#
tid.append(SC.val)
getSym()
else:
mark('identifier expected')
if SC.sym == COLON:
# attribute
write(': ')
writeHtml(': ')
#
getSym()
tp = typ().tp
if tp != None:
for i in tid:
newObj(i, kind(tp))
else:
mark("':' expected")
def typedIds(kind):
if SC.sym == IDENT:
tid = [SC.val]
getSym()
else:
mark("identifier expected")
tid = []
while SC.sym == COMMA:
getSym()
if SC.sym == IDENT:
tid.append(SC.val)
getSym()
else:
mark('identifier expected')
if SC.sym == COLON:
getSym()
tp = typ().val
if tp != None:
for i in tid:
newDecl(i, kind(tp))
else:
mark("':' expected")
def expression():
x = simpleExpression()
while SC.sym in {EQ, NE, LT, LE, GT, GE, ELEMENT, SUBSET, SUPERSET}:
op = SC.sym; getSym()
if op in (EQ, NE, LT, LE, GT, GE):
y = simpleExpression() # x op y
if x.tp == y.tp in (Int, Bool):
if type(x) == Const == type(y): # constant folding
if op == EQ: x.val = int(x.val == y.val)
elif op == NE: x.val = int(x.val != y.val)
elif op == LT: x.val = int(x.val < y.val)
elif op == LE: x.val = int(x.val <= y.val)
elif op == GT: x.val = int(x.val > y.val)
elif op == GE: x.val = int(x.val >= y.val)
x.tp = Bool
else: x = CG.genRelation(op, x, y)
else: mark('bad type')
elif (op == ELEMENT and x.tp == Int) or (op in (SUBSET, SUPERSET) and type(x.tp) == Set):
x = CG.genUnaryOp(op, x); y = simpleExpression()
if type(y.tp) == Set: x = CG.genRelation(op, x, y)
else: mark('set expected')
else: mark('bad type')
return x
def declarations(allocVar):
if SC.sym not in FIRSTDECL | FOLLOWDECL:
getSym()
mark("'begin' or declaration expected")
while SC.sym not in FIRSTDECL | STRONGSYMS | FOLLOWDECL:
getSym()
while SC.sym == CONST:
getSym()
if SC.sym == IDENT:
ident = SC.val
getSym()
if SC.sym == EQ:
getSym()
else:
mark("= expected")
x = expression()
if type(x) == Const:
newDecl(ident, x)
else:
mark('expression not constant')
else:
mark("constant name expected")
if SC.sym == SEMICOLON:
getSym()
else:
mark("; expected")
while SC.sym == TYPE:
getSym()
if SC.sym == IDENT:
ident = SC.val
getSym()
if SC.sym == EQ:
getSym()
else:
mark("= expected")
x = typ()
newDecl(ident, x) # x is of type ST.Type
if SC.sym == SEMICOLON:
getSym()
else:
mark("; expected")
else:
mark("type name expected")
start = len(topScope())
while SC.sym == VAR:
getSym()
typedIds(Var)
if SC.sym == SEMICOLON:
getSym()
else:
mark("; expected")
varsize = allocVar(topScope(), start)
while SC.sym == PROCEDURE:
getSym()
if SC.sym == IDENT:
getSym()
else:
mark("procedure name expected")
ident = SC.val
newDecl(ident, Proc([])) # entered without parameters
sc = topScope()
CG.genProcStart()
openScope() # new scope for parameters and body
if SC.sym == LPAREN:
getSym()
if SC.sym in {VAR, IDENT}:
if SC.sym == VAR:
getSym()
typedIds(Ref)
else:
typedIds(Var)
while SC.sym == SEMICOLON:
getSym()
if SC.sym == VAR:
getSym()
typedIds(Ref)
else:
typedIds(Var)
else:
mark("formal parameters expected")
fp = topScope()
sc[-1].par = fp[:] # procedure parameters updated
if SC.sym == RPAREN:
getSym()
else:
mark(") expected")
else:
fp = []
parsize = CG.genFormalParams(fp)
if SC.sym == SEMICOLON:
getSym()
else:
mark("; expected")
localsize = declarations(CG.genLocalVars)
CG.genProcEntry(ident, parsize, localsize)
x = compoundStatement()
CG.genProcExit(x, parsize, localsize)
closeScope() # scope for parameters and body closed
if SC.sym == SEMICOLON:
getSym()
else:
mark("; expected")
return varsize
def declarations(allocVar):
"""
Parses
declarations =
{"const" ident "=" expression ";"}
{"type" ident "=" type ";"}
{"var" typedIds ";"}
{"procedure" ident ["(" [["var"] typedIds {";" ["var"] typedIds}] ")"] ";"
declarations compoundStatement ";"}.
Updates current scope of symbol table.
Reports an error if an identifier is already defined in the current scope.
For each procedure, code is generated
"""
global depth
if SC.sym not in FIRSTDECL | FOLLOWDECL:
getSym()
mark("'begin' or declaration expected")
while SC.sym not in FIRSTDECL | STRONGSYMS | FOLLOWDECL:
getSym()
while SC.sym == CONST:
# attributes
depth += 1
write(indent * depth)
write('const')
writeln()
writeHtml(htmlIndent * depth)
writeHtml('const')
writeHtmlLn()
#
getSym()
if SC.sym == IDENT:
# attributes
depth += 1
ident = SC.val
write(indent * depth)
write(ident)
writeHtml(htmlIndent * depth)
# integer constant is upright
writeHtml(ident)
#
getSym()
if SC.sym == EQ:
# attribute
write(' = ')
writeHtml(' = ')
#
getSym()
else:
mark("= expected")
x = expression()
if type(x) == Const: newObj(ident, x)
else: mark('expression not constant')
depth -= 1
else:
mark("constant name expected")
if SC.sym == SEMICOLON:
# attributes
write(';')
writeln()
writeHtml(';')
writeHtmlLn()
#
getSym()
else:
mark("; expected")
depth -= 1
while SC.sym == TYPE:
# attributes
depth += 1
write(indent * depth)
write('type')
writeln()
writeHtml(htmlIndent * depth)
writeHtml('type')
writeHtmlLn()
#
getSym()
if SC.sym == IDENT:
# attributes
depth += 1
ident = SC.val
write(indent * depth)
write(ident)
writeHtml(htmlIndent * depth)
writeHtml(ident, _class='ident')
#
getSym()
if SC.sym == EQ:
# attributes
write(' = ')
writeHtml(' = ')
#
getSym()
else:
mark("= expected")
# attributes (emulate stack)
old_depth = depth
depth += 1
x = typ()
depth = old_depth
#
newObj(ident, x) # x is of type ST.Type
if SC.sym == SEMICOLON:
# attribute
write(';')
writeln()
writeHtml(';')
writeHtmlLn()
getSym()
#
else:
mark("; expected")
depth -= 1
else:
mark("type name expected")
depth -= 1
start = len(topScope())
while SC.sym == VAR:
# attributes
depth += 1
write(indent * depth)
write('var')
writeln()
writeHtml(htmlIndent * depth)
writeHtml('var')
writeHtmlLn()
depth += 1
getSym()
write(indent * depth)
write(SC.val)
writeHtml(htmlIndent * depth)
writeHtml(SC.val)
#
typedIds(Var)
if SC.sym == SEMICOLON:
#
write(';')
writeln()
writeHtml(';')
writeHtmlLn()
getSym()
#
else:
mark("; expected")
depth -= 2
varsize = allocVar(topScope(), start)
while SC.sym == PROCEDURE:
#
depth += 1
write(indent * depth)
write('procedure ')
writeHtml(htmlIndent * depth)
writeHtml('procedure ')
#
getSym()
if SC.sym == IDENT:
#
write(SC.val)
writeHtml(SC.val)
#
getSym()
else:
mark("procedure name expected")
ident = SC.val
newObj(ident, Proc([])) # entered without parameters
sc = topScope()
CG.procStart()
openScope() # new scope for parameters and body
if SC.sym == LPAREN:
#
write('(')
writeHtml('(')
#
getSym()
if SC.sym in {VAR, IDENT}:
if SC.sym == VAR:
#
write('var ')
writeHtml('var ')
getSym()
write(SC.val)
writeHtml(SC.val)
#
typedIds(Ref)
else:
typedIds(Var)
while SC.sym == SEMICOLON:
#
write('; ')
writeHtml('; ')
#
getSym()
if SC.sym == VAR:
#
write('var ')
writeHtml('var ')
getSym()
write(SC.val)
writeHtml(SC.val)
#
typedIds(Ref)
else:
#
write(SC.val)
writeHtml(SC.val)
#
typedIds(Var)
else:
mark("formal parameters expected")
fp = topScope()
sc[-1].par = fp[:] # procedure parameters updated
if SC.sym == RPAREN:
#
write(')')
writeHtml(')')
#
getSym()
else:
mark(") expected")
else:
fp = []
parsize = CG.genFormalParams(fp)
if SC.sym == SEMICOLON:
#
write(';')
writeln()
writeHtml(';')
writeHtmlLn()
#
getSym()
else:
mark("; expected")
depth += 1
localsize = declarations(CG.genLocalVars)
CG.genProcEntry(ident, parsize, localsize)
x = compoundStatement(depth + 1)
CG.genProcExit(x, parsize, localsize)
closeScope() # scope for parameters and body closed
if SC.sym == SEMICOLON: getSym()
else: mark("; expected")
depth -= 1
return varsize
def typ():
if SC.sym not in FIRSTTYPE:
getSym()
mark("type expected")
while SC.sym not in FIRSTTYPE | STRONGSYMS | FOLLOWTYPE:
getSym()
if SC.sym == IDENT:
ident = SC.val
x = find(ident)
getSym()
if type(x) == Type:
x = Type(x.val)
else:
mark('not a type')
x = Type(None)
elif SC.sym == ARRAY:
getSym()
if SC.sym == LBRAK:
getSym()
else:
mark("'[' expected")
x = expression()
if SC.sym == PERIOD:
getSym()
else:
mark("'.' expected")
if SC.sym == PERIOD:
getSym()
else:
mark("'.' expected")
y = expression()
if SC.sym == RBRAK:
getSym()
else:
mark("']' expected")
if SC.sym == OF:
getSym()
else:
mark("'of' expected")
z = typ().val
if type(x) != Const or x.val < 0:
mark('bad lower bound')
x = Type(None)
elif type(y) != Const or y.val < x.val:
mark('bad upper bound')
x = Type(None)
else:
x = Type(CG.genArray(Array(z, x.val, y.val - x.val + 1)))
elif SC.sym == RECORD:
getSym()
openScope()
typedIds(Var)
while SC.sym == SEMICOLON:
getSym()
typedIds(Var)
if SC.sym == END:
getSym()
else:
mark("'end' expected")
r = topScope()
closeScope()
x = Type(CG.genRec(Record(r)))
else:
x = Type(None)
return x
def statement():
"""
Parses
statement = ident selector ":=" expression |
ident "(" [expression {"," expression}] ")" |
compoundStatement |
"if" expression "then" Statement ["else" Statement] |
"while" expression "do" Statement.
Generates code for the statement if no error is reported
"""
if SC.sym not in FIRSTSTATEMENT:
mark("statement expected"); getSym()
while SC.sym not in FIRSTSTATEMENT | STRONGSYMS | FOLLOWSTATEMENT:
getSym()
if SC.sym == IDENT:
x = find(SC.val); getSym(); x = genVar(x)
if type(x) in {Var, Ref}:
x = selector(x)
if SC.sym == BECOMES:
getSym(); y = expression()
if x.tp == y.tp in {Bool, Int}:
if type(x) == Var: x = genAssign(x, y)
else: mark('illegal assignment')
else: mark('incompatible assignment')
elif SC.sym == EQ:
mark(':= expected'); getSym(); y = expression()
else: mark(':= expected')
elif type(x) in {Proc, StdProc} and SC.sym == LPAREN:
getSym()
fp, i = x.par, 0 # list of formal parameters
if SC.sym in FIRSTEXPRESSION:
y = expression()
if i < len(fp):
if type(fp[i]) == Var or type(y) == Var: # fp[i] == Ref and ty
if type(x) == Proc: genActualPara(y, fp[i], i)
i = i + 1
else: mark('illegal parameter mode')
else: mark('extra parameter')
while SC.sym == COMMA:
getSym()
y = expression()
if i < len(fp):
if type(fp[i]) == Var or type(y) == Var:
if type(x) == Proc: genActualPara(y, fp[i], i)
i = i + 1
else: mark('illegal parameter mode')
else: mark('extra parameter')
if i < len(fp): mark('too few parameters')
if SC.sym == RPAREN: getSym()
else: mark("')' expected")
if type(x) == StdProc:
if x.name == 'read': x = genRead(y)
elif x.name == 'write': x = genWrite(y)
elif x.name == 'writeln': x = genWriteln()
else: x = genCall(x)
else: mark("variable or procedure expected")
elif SC.sym == BEGIN: x = compoundStatement()
elif SC.sym == IF:
getSym(); x = expression(); q=1;
if x.tp == Bool: x = genCond(x)
elif x.tp == Int: q = 0 # if we skipped genrelation, prepare to skip following statement
def factor():
if SC.sym == IDENT:
x = find(SC.val)
if type(x) == Var: x = CG.genVar(x); getSym()
elif type(x) == Const: x = Const(x.tp, x.val); x = CG.genConst(x); getSym()
else: mark('variable or constant identifier expected')
x = selector(x)
elif SC.sym == NUMBER:
x = Const(Int, SC.val); x = CG.genConst(x); getSym()
elif SC.sym == LPAREN:
getSym(); x = expression()
if SC.sym == RPAREN: getSym()
else: mark(') expected')
elif SC.sym == LBRACE:
getSym()
if SC.sym in FIRSTEXPRESSION:
y = expression()
if y.tp == Int: x = CG.genUnaryOp(SET, y)
else: mark('not integer')
while SC.sym == COMMA:
getSym(); y = expression()
if y.tp == Int: y = CG.genUnaryOp(SET, y)
else: mark("not integer")
x = CG.genBinaryOp(UNION, x, y)
else: x = Const(Set(0, 32), 0); x = CG.genConst(x)
if SC.sym == RBRACE: getSym()
else: mark('} expected')
elif SC.sym == NOT:
getSym(); x = factor()
if x.tp != Bool: mark('not boolean')
elif type(x) == Const: x.val = 1 - x.val # constant folding
else: x = CG.genUnaryOp(NOT, x)
elif SC.sym in {CARD, COMPLEMENT}:
op = SC.sym; getSym(); x = factor()
if type(x.tp) == Set: x = CG.genUnaryOp(op, x)
else: mark('set expected')
else: mark('expression expected')
return x
def declarations(allocVar):
"""
Parses
declarations =
{"const" ident "=" expression ";"}
{"type" ident "=" type ";"}
{"var" typedIds ";"}
{"procedure" ident ["(" [["var"] typedIds {";" ["var"] typedIds}] ")"] ";"
declarations compoundStatement ";"}.
Updates current scope of symbol table.
Reports an error if an identifier is already defined in the current scope.
For each procedure, code is generated
"""
if SC.sym not in FIRSTDECL | FOLLOWDECL:
getSym()
mark("declaration expected")
while SC.sym not in FIRSTDECL | FOLLOWDECL:
getSym()
while SC.sym == CONST:
getSym()
if SC.sym == IDENT:
ident = SC.val
getSym()
if SC.sym == EQ:
getSym()
else:
mark("= expected")
x = expression()
if type(x) == Const:
newObj(ident, x)
else:
mark("expression not constant")
else:
mark("constant name expected")
if SC.sym == SEMICOLON:
getSym()
else:
mark("; expected")
while SC.sym == TYPE:
getSym()
if SC.sym == IDENT:
ident = SC.val
getSym()
if SC.sym == EQ:
getSym()
else:
mark("= expected")
x = typ()
newObj(ident, x) # x is of type ST.Type
if SC.sym == SEMICOLON:
getSym()
else:
mark("; expected")
else:
print(SC.sym)
mark("type name expected")
start = len(topScope())
while SC.sym == VAR:
getSym()
typedIds(Var)
if SC.sym == SEMICOLON:
getSym()
else:
mark("; expected")
varsize = allocVar(topScope(), start)
while SC.sym == PROCEDURE:
getSym()
if SC.sym == IDENT:
getSym()
else:
mark("procedure name expected")
ident = SC.val
newObj(ident, Proc([])) # entered without parameters
sc = topScope()
procStart()
openScope() # new scope for parameters and body
if SC.sym == LPAREN:
getSym()
if SC.sym in {VAR, IDENT}:
if SC.sym == VAR:
getSym()
typedIds(Ref) # , procParams)
else:
typedIds(Var) # , procParams)
while SC.sym == SEMICOLON:
getSym()
if SC.sym == VAR:
getSym()
typedIds(Ref) # , procParams)
else:
typedIds(Var) # , procParams)
else:
mark("formal parameters expected")
fp = topScope()
sc[-1].par = fp[:] # procedure parameters updated
if SC.sym == RPAREN:
getSym()
else:
mark(") expected")
else:
fp = []
parsize = genFormalParams(fp)
if SC.sym == SEMICOLON:
getSym()
else:
mark("; expected")
localsize = declarations(genLocalVars)
genProcEntry(ident, parsize, localsize)
x = compoundStatement()
genProcExit(x, parsize, localsize)
closeScope() # scope for parameters and body closed
if SC.sym == SEMICOLON:
getSym()
else:
mark("; expected")
return varsize
def selector(x):
while SC.sym in {LBRAK, PERIOD}:
if SC.sym == LBRAK: # x[y]
getSym(); y = expression()
if type(x.tp) == Array:
if y.tp == Int:
if type(y) == Const and (y.val < x.tp.lower or y.val >= x.tp.lower + x.tp.length):
mark('index out of bounds')
else: x = CG.genIndex(x, y)
else: mark('index not integer')
else: mark('not an array')
if SC.sym == RBRAK: getSym()
else: mark("] expected")
else: # x.f
getSym()
if SC.sym == IDENT:
if type(x.tp) == Record:
for f in x.tp.fields:
if f.name == SC.val:
x = CG.genSelect(x, f); break
else: mark("not a field")
getSym()
else: mark("not a record")
else: mark("identifier expected")
return x
def typedIds():
if SC.sym == IDENT: tid = [SC.val]; getSym()
else: mark("identifier expected")
while SC.sym == COMMA:
getSym()
if SC.sym == IDENT: tid.append(SC.val); getSym()
else: mark('identifier expected')
if SC.sym == COLON: getSym()
else: mark("':' expected")
tp = typ().val
for i in tid: newDecl(i, Var(tp))
while SC.sym == COMMA:
getSym()
if SC.sym == IDENT: tid = [SC.val]; getSym()
else: mark("identifier expected")
while SC.sym == COMMA:
getSym()
if SC.sym == IDENT: tid.append(SC.val); getSym()
else: mark('identifier expected')
if SC.sym == COLON: getSym()
else: mark("':' expected")
tp = typ().val
for i in tid: newDecl(i, Var(tp))
def statementBlock():
x = statementList()
while SC.sym in FIRSTSTATEMENT:
if not SC.newline: mark('new line expected')
y = statementList(); x = CG.genSeq(x, y)
return x
def typ():
"""
Parses
type = ident |
"array" "[" expression ".." expression "]" "of" type |
"record" typedIds {";" typedIds} "end".
Returns a type descriptor
"""
global depth
if SC.sym not in FIRSTTYPE:
getSym()
mark("type expected")
while SC.sym not in FIRSTTYPE | STRONGSYMS | FOLLOWTYPE:
getSym()
if SC.sym == IDENT:
# attribute
ident = SC.val
write(ident)
writeHtml(ident, _class='ident')
#
x = find(ident)
getSym()
if type(x) == Type: x = Type(x.tp)
else:
mark('not a type')
x = Type(None)
elif SC.sym == ARRAY:
depth += 1
# attribute
writeln()
write(indent * depth)
write('array ')
writeHtmlLn()
writeHtml(htmlIndent * depth)
writeHtml('array ')
#
getSym()
if SC.sym == LBRAK:
# attribute
write('[')
writeHtml('[')
#
getSym()
else:
mark("'[' expected")
x = expression()
if SC.sym == PERIOD:
# attribute
write(' .')
writeHtml(' .')
#
getSym()
else:
mark("'.' expected")
if SC.sym == PERIOD:
# attribute
write('. ')
writeHtml('. ')
#
getSym()
else:
mark("'.' expected")
y = expression()
if SC.sym == RBRAK:
# attribute
write('] ')
writeHtml('] ')
#
getSym()
else:
mark("']' expected")
if SC.sym == OF:
# attribute
write('of')
writeHtml('of')
#
getSym()
else:
mark("'of' expected")
z = typ().tp
if type(x) != Const or x.val < 0:
mark('bad lower bound')
x = Type(None)
elif type(y) != Const or y.val < x.val:
mark('bad upper bound')
y = Type(None)
else:
x = Type(CG.genArray(Array(z, x.val, y.val - x.val + 1)))
depth -= 1
elif SC.sym == RECORD:
# attributes
depth += 1
writeln()
write(indent * depth)
write('record')
writeln()
writeHtmlLn()
writeHtml(htmlIndent * depth)
writeHtml('record')
writeHtmlLn()
depth += 1
#
getSym()
# attributes
write(indent * depth)
write(SC.val)
writeHtml(htmlIndent * depth)
writeHtml(SC.val)
#
openScope()
typedIds(Var)
while SC.sym == SEMICOLON:
# attributes
write(';')
writeln()
writeHtml(';')
writeHtmlLn()
#
getSym()
# attributes
write(indent * depth)
write(SC.val)
writeHtml(htmlIndent * depth)
writeHtml(SC.val)
#
typedIds(Var)
# attributes
writeln()
writeHtmlLn()
depth -= 1
write(indent * depth)
writeHtml(htmlIndent * depth)
#
if SC.sym == END:
# attributes
write('end')
writeHtml('end')
#
getSym()
else:
mark("'end' expected")
r = topScope()
closeScope()
x = Type(CG.genRec(Record(r)))
depth -= 1
else:
x = Type(None)
return x
def statement(l):
"""
Parses
statement =
EDIT LINE ident selector ":=" expression |
ident «write(l * indent + ident)» "(" «write('(')» [expression
{"," «write(', ')» expression}] ")" «write(')')» |
compoundStatement(l) |
"if" «writeln; write(l * indent + 'if ')» expression
"then" «write(' then')» statement(l + 1)
["else" «writeln; write(l * indent + 'else')» statement(l + 1)] |
EDIT LINE "while" expression "do" statement.
Generates code for the statement if no error is reported
"""
if SC.sym not in FIRSTSTATEMENT:
mark("statement expected")
getSym()
while SC.sym not in FIRSTSTATEMENT | STRONGSYMS | FOLLOWSTATEMENT:
getSym()
if SC.sym == IDENT:
x = find(SC.val)
writeln()
write(l * indent + SC.val)
getSym()
writeHtmlLn()
writeHtml(l * htmlIndent + SC.val)
x = CG.genVar(x)
if type(x) in {Var, Ref}:
x = selector(x)
if SC.sym == BECOMES:
write(' := ')
writeHtml(' := ')
getSym()
y = expression()
if x.tp == y.tp in {
Bool, Int
}: # and not SC.error: type(y) could be Type
#if type(x) == Var: ### and type(y) in {Var, Const}: incomplete, y may be Reg
x = CG.genAssign(x, y)
#else: mark('illegal assignment')
else:
mark('incompatible assignment')
elif SC.sym == EQ:
mark(':= expected')
getSym()
y = expression()
else:
mark(':= expected')
elif type(x) in {Proc, StdProc}:
fp, i = x.par, 0 # list of formals, count of actuals
if SC.sym == LPAREN:
write('(')
getSym()
writeHtml('(')
if SC.sym in FIRSTEXPRESSION:
y = expression()
if i < len(fp):
if (type(fp[i]) == Var or type(y) == Var) and \
fp[i].tp == y.tp:
if type(x) == Proc: CG.genActualPara(y, fp[i], i)
i = i + 1
else:
mark('illegal parameter mode')
else:
mark('extra parameter')
while SC.sym == COMMA:
write(', ')
getSym()
writeHtml(', ')
y = expression()
if i < len(fp):
if (type(fp[i]) == Var or type(y) == Var) and \
fp[i].tp == y.tp:
if type(x) == Proc:
CG.genActualPara(y, fp[i], i)
i = i + 1
else:
mark('illegal parameter mode')
else:
mark('extra parameter')
if SC.sym == RPAREN:
write(')')
getSym()
writeHtml(')')
else:
mark("')' expected")
if i < len(fp): mark('too few parameters')
if type(x) == StdProc:
if x.name == 'read': x = CG.genRead(y)
elif x.name == 'write': x = CG.genWrite(y)
elif x.name == 'writeln': x = CG.genWriteln()
else: x = CG.genCall(x)
else: mark("variable or procedure expected")
elif SC.sym == BEGIN: x = compoundStatement(l + 1)
elif SC.sym == IF:
writeln()
write(l * indent + 'if ')
writeHtmlLn()
writeHtml(l * htmlIndent + 'if ')
getSym()
x = expression()
if x.tp == Bool: x = CG.genCond(x)
else: mark('boolean expected')
if SC.sym == THEN:
write(' then')
writeHtml(' then')
getSym()
else:
mark("'then' expected")
y = statement(l + 1)
if SC.sym == ELSE:
if x.tp == Bool: y = CG.genThen(x, y)
writeln()
write(l * indent + 'else')
writeHtmlLn()
writeHtml(l * htmlIndent + ' else')
getSym()
z = statement(l + 1)
if x.tp == Bool: x = CG.genIfElse(x, y, z)
else:
if x.tp == Bool: x = CG.genIfThen(x, y)
elif SC.sym == WHILE:
writeln()
write(indent * (l + 1))
write('while ')
writeHtmlLn()
writeHtml(htmlIndent * (l + 1))
writeHtml('while ')
getSym()
t = CG.genTarget()
x = expression()
if x.tp == Bool: x = CG.genCond(x)
else: mark('boolean expected')
if SC.sym == DO:
write(' do')
writeHtml(' do')
getSym()
else:
mark("'do' expected")
y = statement(l + 2)
if x.tp == Bool: x = CG.genWhile(t, x, y)
else: x = None
return x
def statement():
"""
Parses
statement = ident selector ":=" expression |
ident "(" [expression {"," expression}] ")" |
compoundStatement |
"if" expression "then" Statement ["else" Statement] |
"while" expression "do" Statement.
Generates code for the statement if no error is reported
"""
if SC.sym not in FIRSTSTATEMENT:
mark("statement expected")
getSym()
while SC.sym not in FIRSTSTATEMENT | STRONGSYMS | FOLLOWSTATEMENT:
getSym()
if SC.sym == IDENT:
x = find(SC.val)
getSym()
x = genVar(x)
if type(x) in {Var, Ref}:
x = selector(x)
if SC.sym == BECOMES:
getSym()
y = expression()
if x.tp == y.tp in {Bool, Int}:
# if type(x) == Var: x = genAssign(x, y)
if type(x) == Var:
print("x: ", x, "y: ", y)
x = genAssign2(x, y)
else:
mark("illegal assignment")
else:
mark("incompatible assignment")
elif SC.sym == EQ:
mark(":= expected")
getSym()
y = expression()
else:
mark(":= expected")
elif type(x) in {Proc, StdProc} and SC.sym == LPAREN:
getSym()
fp, i = x.par, 0 # list of formal parameters
if SC.sym in FIRSTEXPRESSION:
y = expression()
if i < len(fp):
if type(fp[i]) == Var or type(y) == Var: # fp[i] == Ref and ty
if type(x) == Proc:
genActualPara(y, fp[i], i)
i = i + 1
else:
mark("illegal parameter mode")
else:
mark("extra parameter")
while SC.sym == COMMA:
getSym()
y = expression()
if i < len(fp):
if type(fp[i]) == Var or type(y) == Var:
if type(x) == Proc:
genActualPara(y, fp[i], i)
i = i + 1
else:
mark("illegal parameter mode")
else:
mark("extra parameter")
if i < len(fp):
mark("too few parameters")
if SC.sym == RPAREN:
getSym()
else:
mark("')' expected")
if type(x) == StdProc:
if x.name == "read":
x = genRead(y)
elif x.name == "write":
x = genWrite(y)
elif x.name == "writeln":
x = genWriteln()
else:
x = genCall(x)
else:
mark("variable or procedure expected")
elif SC.sym == BEGIN:
x = compoundStatement()
elif SC.sym == IF:
getSym()
x = expression()
if x.tp == Bool:
x = genCond(x)
else:
mark("boolean expected")
if SC.sym == THEN:
getSym()
else:
mark("'then' expected")
y = statement()
if SC.sym == ELSE:
y = genThen(x, y)
getSym()
z = statement()
x = genIfElse(x, y, z)
else:
x = genIfThen(x, y)
elif SC.sym == WHILE:
getSym()
t = genTarget()
x = expression()
if x.tp == Bool:
x = genCond(x)
else:
mark("boolean expected")
if SC.sym == DO:
getSym()
else:
mark("'do' expected")
y = statement()
x = genWhile(t, x, y)
else:
mark("invalid statement")
x = None
return x
else: mark('extra parameter')
if i < len(fp): mark('too few parameters')
if SC.sym == RPAREN: getSym()
else: mark("')' expected")
if type(x) == StdProc:
if x.name == 'read': x = genRead(y)
elif x.name == 'write': x = genWrite(y)
elif x.name == 'writeln': x = genWriteln()
else: x = genCall(x)
else: mark("variable or procedure expected")
elif SC.sym == BEGIN: x = compoundStatement()
elif SC.sym == IF:
getSym(); x = expression(); q=1;
if x.tp == Bool: x = genCond(x)
elif x.tp == Int: q = 0 # if we skipped genrelation, prepare to skip following statement
else: mark('boolean expected')
if SC.sym == THEN: getSym()
else: mark("'then' expected")
if q=1: y = statement() # if (FALSE (q=0)) skip
if SC.sym == ELSE and q=1: # if (TRUE (q=1)) then perform THEN
y = genThen(x, y); getSym(); z = statement();
x = genIfElse(x, y, z)
else: x = genIfThen(x, y)
elif SC.sym == WHILE:
getSym(); t = genTarget(); x = expression()
if x.tp == Bool: x = genCond(x)
else: mark('boolean expected')
if SC.sym == DO: getSym()
else: mark("'do' expected")
y = statement(); x = genWhile(t, x, y)
else:
def statement():
if SC.sym == IDENT: # x := y, y(...), x ← y(...)
# type(x) == Proc, StdProc: check no result parameters needed; call, y := true, x
# type(x) ≠ Proc, StdProc: x := selector():
# sym == BECOMES: assignment; call := false
# sym == LARROW: check result paramter match, type(y) is Proc, StdProc,
x = find(SC.val)
if type(x) in {Proc, StdProc}: # procedure call without result
if x.res != []: mark('variable for result expected')
getSym(); call, xs, y = True, [], x
elif type(x) == Var: # assignment or procedure call with result
x = find(SC.val); x = CG.genVar(x); getSym()
if SC.sym in FIRSTSELECTOR:
xs = [CG.genLeftAssign(selector(x))] # array or field update
else: # multiple assignment or procedure call with result
xs = [CG.genLeftAssign(x)]
while SC.sym == COMMA:
getSym();
if SC.sym == IDENT:
x = find(SC.val)
if x.name not in {x.name for x in xs}:
if type(x) == Var:
xs += [CG.genLeftAssign(CG.genVar(x))]; getSym()
else: mark('variable identifier expected')
else: mark('duplicate variable identifier')
else: mark('identifier expected')
if SC.sym == BECOMES:
getSym(); call = False; ys = [CG.genRightAssign(expression())] # xs := ys
while SC.sym == COMMA: getSym(); ys += [CG.genRightAssign(expression())]
if len(xs) == len(ys):
for x, y in zip(reversed(xs), reversed(ys)):
if compatible(x.tp, y.tp): x = CG.genAssign(x, y)
else: mark('incompatible assignment')
else: mark('unbalanced assignment')
elif SC.sym == LARROW:
getSym()
if SC.sym == IDENT: y = find(SC.val); getSym(); call = True
else: mark('procedure identifier expected')
if type(y) in {Proc, StdProc}:
if len(xs) == len(y.res):
for x, r in zip(xs, y.res):
if not compatible(x.tp, r.tp): mark('incompatible call')
else: mark('unbalanced call')
else: mark('procedure expected')
else: mark(':= or ← expected')
else: mark("variable or procedure expected")
if call: # call y(ap) or xs ← y(ap)
fp, ap, i = y.par, [], 0 # list of formals, list of actuals
if SC.sym == LPAREN: getSym()
else: mark("'(' expected")
if SC.sym in FIRSTEXPRESSION:
a = expression()
if i < len(fp):
if compatible(fp[i].tp, a.tp):
ap.append(CG.genActualPara(a, fp[i], i))
else: mark('incompatible parameter')
else: mark('extra parameter')
i = i + 1
while SC.sym == COMMA:
getSym()
a = expression()
if i < len(fp):
if compatible(fp[i].tp, a.tp):
ap.append(CG.genActualPara(a, fp[i], i))
else: mark('incompatible parameter')
else: mark('extra parameter')
i = i + 1
if SC.sym == RPAREN: getSym()
else: mark("')' expected")
if i < len(fp): mark('too few parameters')
elif type(y) == StdProc:
if y.name == 'read': x = CG.genRead(x)
elif y.name == 'write': x = CG.genWrite(a)
elif y.name == 'writeln': x = CG.genWriteln()
else: x = CG.genCall(xs, y, ap)
elif SC.sym == IF:
getSym(); x = expression();
if x.tp == Bool: x = CG.genThen(x)
else: mark('boolean expected')
if SC.sym == THEN: getSym()
else: mark("'then' expected")
y = statementSuite()
if SC.sym == ELSE:
getSym()
y = CG.genElse(x, y)
z = statementSuite()
x = CG.genIfElse(x, y, z)
else:
x = CG.genIfThen(x, y)
elif SC.sym == WHILE:
getSym(); t = CG.genWhile(); x = expression()
if x.tp == Bool: x = CG.genDo(x)
else: mark('boolean expected')
if SC.sym == DO: getSym()
else: mark("'do' expected")
y = statementSuite()
x = CG.genWhileDo(t, x, y)
else: mark('statement expected')
return x
def testRange(x):
if x.val >= 0x8000 or x.val < -0x8000: mark('value too large')
def typ():
if SC.sym == IDENT:
ident = SC.val; x = find(ident)
if type(x) == Type: x = Type(x.val); getSym()
else: mark('type identifier expected')
elif SC.sym == LBRAK:
getSym(); x = expression()
if SC.sym == DOTDOT: getSym()
else: mark("'..' expected")
y = expression()
if SC.sym == RBRAK: getSym()
else: mark("']' expected")
if SC.sym == RARROW: getSym()
else: mark("'→' expected")
z = typ().val;
if type(x) != Const or x.val < 0: mark('bad lower bound')
elif type(y) != Const or y.val < x.val: mark('bad upper bound')
else: x = Type(CG.genArray(Array(z, x.val, y.val - x.val + 1)))
elif SC.sym == LPAREN:
getSym(); openScope(); typedIds()
if SC.sym == RPAREN: getSym()
else: mark("')' expected")
r = topScope(); closeScope()
x = Type(CG.genRec(Record(r)))
elif SC.sym == FULLPAREN:
pass
elif SC.sym == SET:
getSym();
if SC.sym == LBRAK: getSym()
else: mark ("'[' expected")
x = expression()
if SC.sym == DOTDOT: getSym()
else: mark("'..' expected")
y = expression()
if SC.sym == RBRAK: getSym()
else: mark("']' expected")
if type(x) != Const: mark('bad lower bound')
elif type(y) != Const or y.val < x.val: mark('bad upper bound')
else: x = Type(CG.genSet(Set(x.val, y.val - x.val + 1)))
else: mark('type expected')
return x
def find(name):
for l in symTab:
for e in l:
if name == e.name: return e
mark('undefined identifier ' + name)
return Const(None, 0)
def declarations(allocVar):
while SC.sym == CONST:
getSym()
if SC.sym == IDENT: ident = SC.val; getSym()
else: mark("constant name expected")
if SC.sym == EQ: getSym()
else: mark("= expected")
x = expression()
if type(x) == Const: newDecl(ident, x)
else: mark('expression not constant')
while SC.sym == TYPE:
getSym()
if SC.sym == IDENT: ident = SC.val; getSym()
else: mark("type name expected")
if SC.sym == EQ: getSym()
else: mark("= expected")
x = typ(); newDecl(ident, x) # x is of type ST.Type
start = len(topScope())
while SC.sym == VAR:
getSym(); typedIds()
var = allocVar(topScope(), start)
while SC.sym == PROCEDURE:
getSym()
if SC.sym == LPAREN:
getSym()
if SC.sym == IDENT: r = SC.val; getSym()
else: mark("identifier expected")
if SC.sym == COLON: getSym()
else: mark("':' expected")
tp = typ().val
if SC.sym == RPAREN: getSym()
else: mark(") expected")
else: r = None
if SC.sym == IDENT: ident = SC.val; getSym()
else: mark("procedure name expected")
newDecl(ident, Proc([], [])) # entered without parameters
sc = topScope(); openScope() # new scope for parameters and body
if r: newDecl(r, Var(tp))
if SC.sym == LPAREN: getSym()
else: mark("( expected")
if SC.sym == IDENT: typedIds()
fp = topScope()
if SC.sym == RPAREN: getSym()
else: mark(") expected")
d = len(fp)
if SC.sym == RARROW:
getSym()
if SC.sym == LPAREN: getSym()
else: mark('( expected')
typedIds()
if SC.sym == RPAREN: getSym()
else: mark(') expected')
sc[-1].par, sc[-1].res = fp[:d], fp[d:] # procedure parameters updated
para = CG.genProcStart(ident, fp[:d], fp[d:])
body(ident, para); closeScope() # scope for parameters and body closed
return var
def compileFile(srcfn):
if srcfn.endswith('.p'):
with open(srcfn, 'r') as f: src = f.read()
dstfn = srcfn[:-2] + '.s'
compileString(src, dstfn)
else: mark("'.p' file extension expected")
def selector(x):
"""
Parses
selector = {"." ident | "[" expression "]"}.
Assumes x is the entry for the identifier in front of the selector;
generates code for the selector if no error is reported
"""
while SC.sym in {PERIOD, LBRAK}:
if SC.sym == PERIOD: # x.f
# attribute
write('.')
writeHtml('.')
#
getSym()
if SC.sym == IDENT:
# attribute
write(SC.val)
writeHtml(SC.val)
#
if type(x.tp) == Record:
for f in x.tp.fields:
if f.name == SC.val:
x = CG.genSelect(x, f)
break
else:
mark("not a field")
getSym()
else:
mark("not a record")
else:
mark("identifier expected")
else: # x[y]
getSym()
# attribute
write('[')
writeHtml('[')
#
y = expression()
if type(x.tp) == Array:
if y.tp == Int:
if type(y) == Const and \
(y.val < x.tp.lower or y.val >= x.tp.lower + x.tp.length):
mark('index out of bounds')
else:
x = CG.genIndex(x, y)
else:
mark('index not integer')
else:
mark('not an array')
if SC.sym == RBRAK:
getSym()
# attribute
write(']')
writeHtml(']')
else:
mark("] expected")
return x
def typ():
"""
Parses
type = ident |
"array" "[" expression ".." expression "]" "of" type |
"record" typedIds {";" typedIds} "end".
Returns a type descriptor
"""
if SC.sym not in FIRSTTYPE:
getSym()
mark("type expected")
while SC.sym not in FIRSTTYPE | FOLLOWTYPE | STRONGSYMS:
getSym()
if SC.sym == IDENT:
ident = SC.val
x = find(ident)
getSym()
if type(x) == Type:
x = Type(x.tp)
else:
mark("not a type")
elif SC.sym == ARRAY:
getSym()
if SC.sym == LBRAK:
getSym()
else:
mark("'[' expected")
x = expression()
if type(x) != Const or x.val < 0:
mark("bad lower bound")
if SC.sym == PERIOD:
getSym()
else:
mark("'.' expected")
if SC.sym == PERIOD:
getSym()
else:
mark("'.' expected")
y = expression()
if type(y) != Const or y.val < x.val:
mark("bad upper bound")
if SC.sym == RBRAK:
getSym()
else:
mark("']' expected")
if SC.sym == OF:
getSym()
else:
mark("'of' expected")
z = typ().tp
l = y.val - x.val + 1
x = Type(genArray(Array(z, x.val, l)))
elif SC.sym == RECORD:
getSym()
openScope()
typedIds(Var)
while SC.sym == SEMICOLON:
getSym()
typedIds(Var)
if SC.sym == END:
getSym()
else:
mark("'end' expected")
r = topScope()
closeScope()
x = Type(genRec(Record(r)))
else:
mark("type expected")
x = Type(None)
return x
def obtainReg():
if len(regs) == 0:
mark('out of registers')
return R0
else:
return regs.pop()
def statement():
if SC.sym not in FIRSTSTATEMENT:
mark("statement expected")
getSym()
while SC.sym not in FIRSTSTATEMENT | STRONGSYMS | FOLLOWSTATEMENT:
getSym()
if SC.sym == IDENT:
x = find(SC.val)
getSym()
if type(x) in {Var, Ref}:
x = CG.genVar(x)
x = selector(x)
if SC.sym == BECOMES:
getSym()
y = expression()
if x.tp == y.tp in {Bool, Int}:
x = CG.genAssign(x, y)
else:
mark('incompatible assignment')
elif SC.sym == EQ:
mark(':= expected')
getSym()
y = expression()
else:
mark(':= expected')
elif type(x) in {Proc, StdProc}:
fp, ap, i = x.par, [], 0 # list of formals, list of actuals
if SC.sym == LPAREN:
getSym()
if SC.sym in FIRSTEXPRESSION:
y = expression()
if i < len(fp):
if (type(fp[i]) == Var or type(y) == Var) and \
fp[i].tp == y.tp:
if type(x) == Proc:
ap.append(CG.genActualPara(y, fp[i], i))
else:
mark('illegal parameter mode')
else:
mark('extra parameter')
i = i + 1
while SC.sym == COMMA:
getSym()
y = expression()
if i < len(fp):
if (type(fp[i]) == Var or type(y) == Var) and \
fp[i].tp == y.tp:
if type(x) == Proc:
ap.append(CG.genActualPara(y, fp[i], i))
else:
mark('illegal parameter mode')
else:
mark('extra parameter')
i = i + 1
if SC.sym == RPAREN:
getSym()
else:
mark("')' expected")
if i < len(fp):
mark('too few parameters')
elif type(x) == StdProc:
if x.name == 'read':
x = CG.genRead(y)
elif x.name == 'write':
x = CG.genWrite(y)
elif x.name == 'writeln':
x = CG.genWriteln()
else:
x = CG.genCall(x, ap)
else:
mark("variable or procedure expected")
elif SC.sym == BEGIN:
x = compoundStatement()
elif SC.sym == IF:
getSym()
x = expression()
if x.tp == Bool:
x = CG.genCond(x)
else:
mark('boolean expected')
if SC.sym == THEN:
getSym()
else:
mark("'then' expected")
y = statement()
if SC.sym == ELSE:
if x.tp == Bool: y = CG.genThen(x, y)
getSym()
z = statement()
if x.tp == Bool: x = CG.genIfElse(x, y, z)
else:
if x.tp == Bool: x = CG.genIfThen(x, y)
elif SC.sym == WHILE:
getSym()
t = CG.genTarget()
x = expression()
if x.tp == Bool:
x = CG.genCond(x)
else:
mark('boolean expected')
if SC.sym == DO:
getSym()
else:
mark("'do' expected")
y = statement()
if x.tp == Bool: x = CG.genWhile(t, x, y)
else:
x = None
return x
def testRange(x):
"""Check if x is suitable for immediate addressing"""
if x.val >= 0x8000 or x.val < -0x8000:
mark("value too large")
def selector(x):
"""
Parses
selector = {"." ident | "[" expression "]"}.
Assumes x is the entry for the identifier in front of the selector;
generates code for the selector if no error is reported
"""
while SC.sym in {PERIOD, LBRAK}:
if SC.sym == PERIOD: # x.f
getSym()
if SC.sym == IDENT:
if type(x.tp) == Record:
for f in x.tp.fields:
if f.name == SC.val:
x = genSelect(x, f)
break
else:
mark("not a field")
getSym()
else:
mark("not a record")
else:
mark("identifier expected")
else: # x[y]
getSym()
y = expression()
if type(x.tp) == Array:
if y.tp == Int:
if type(y) == Const and (y.val < x.tp.lower or y.val >= x.tp.lower + x.tp.length):
mark("index out of bounds")
else:
x = genIndex(x, y)
else:
mark("index not integer")
else:
mark("not an array")
if SC.sym == RBRAK:
getSym()
else:
mark("] expected")
return x
def obtainReg():
if len(regs) == 0:
mark("out of registers")
return R0
else:
return regs.pop()
def newObj(name, entry):
top, entry.lev, entry.name = symTab[0], len(symTab) - 1, name
for e in top:
if e.name == name:
mark("multiple definition"); return
top.append(entry)