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 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", 37)
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', 38)
elif SC.sym == ARRAY:
getSym()
if SC.sym == LBRAK: getSym()
else: mark("'[' expected", 39)
x = expression()
if type(x) != Const or x.val < 0: mark('bad lower bound', 40)
if SC.sym == PERIOD: getSym()
else: mark("'.' expected", 41)
if SC.sym == PERIOD: getSym()
else: mark("'.' expected", 42)
y = expression()
if type(y) != Const or y.val < x.val: mark('bad upper bound', 43)
if SC.sym == RBRAK: getSym()
else: mark("']' expected", 44)
if SC.sym == OF: getSym()
else: mark("'of' expected", 45)
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", 46)
r = topScope()
closeScope()
x = Type(genRec(Record(r)))
else:
mark("type expected", 47)
x = Type(None)
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)
writeHtml(SC.val)
getSym()
x = selector(x)
elif SC.sym == NUMBER:
x = Const(Int, SC.val)
x = CG.genConst(x)
write(str(SC.val))
writeHtml(str(SC.val))
getSym()
elif SC.sym == LPAREN:
write('(')
writeHtml('(')
getSym()
x = expression()
if SC.sym == RPAREN:
write(')')
writeHtml(')')
getSym()
else:
mark(") expected")
elif SC.sym == NOT:
write('not ')
writeHtml('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 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 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 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 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", 8)
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', 9)
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", 10)
elif SC.sym == NOT:
getSym()
x = factor()
if x.tp != Bool: mark('not boolean', 11)
elif type(x) == Const: x.val = 1 - x.val # constant folding
else: x = genUnaryOp(NOT, x)
else:
mark("factor expected", 12)
x = None
return x
def factor():
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')
getSym()
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 == 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 == TILDE:
getSym()
x = factor()
if x.tp != Int: mark('not integer')
elif type(x) == Const: x.val = ~x.val # constant folding
else: x = CG.genUnaryOp(TILDE, x)
else: x = Const(None, 0)
return x
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 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", 20)
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', 21)
else:
mark('incompatible assignment', 22)
elif SC.sym == EQ:
mark(':= expected', 23)
getSym()
y = expression()
else:
mark(':= expected', 24)
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:
if type(x) == Proc:
genActualPara(y, fp[i], i)
#i = i + 1
else:
mark('illegal parameter mode', 25)
i = i + 1
else:
mark('extra parameter', 26)
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', 27)
i = i + 1
else:
mark('extra parameter', 28)
if i < len(fp): mark('too few parameters', 29)
#if i > 0: mark('too few parameters')
if SC.sym == RPAREN: getSym()
else: mark("')' expected", 30)
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", 31)
elif SC.sym == BEGIN: x = compoundStatement()
elif SC.sym == IF:
getSym()
x = expression()
# if x.tp == Bool: x = genCond(x)
# else: mark('boolean expected', 32)
# if SC.sym == THEN: getSym()
# else: mark("'then' expected", 33)
# y = statement()
# if SC.sym == ELSE:
# y = genThen(x, y); getSym(); z = statement();
# x = genIfElse(x, y, z)
# else: x = genIfThen(x, y)
# eliminate dead code resulting from boolean constants
if x.tp != Bool:
mark('boolean expected', 32)
if SC.sym == THEN: getSym()
else: mark("'then' expected", 33)
if type(x) == Const and x.val == 1: # if true then S -> S
x = statement()
if SC.sym == ELSE: # if true then S else T -> S
getSym()
CG.emit = False
statement() # T
CG.emit = True
elif type(x) == Const and x.val == 0: # if false then S -> skip
CG.emit = False
statement()
CG.emit = True
if SC.sym == ELSE: # if false then S else T -> T
getSym()
x = statement() #T
else:
# then
x = genCond(x)
# S
y = statement()
#print("IF S: "+str(y))
if SC.sym == ELSE:
y = genThen(x, y)
getSym()
z = statement()
x = genIfElse(x, y, z)
else:
#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', 34)
if SC.sym == DO: getSym()
else: mark("'do' expected", 35)
y = statement()
x = genWhile(t, x, y)
else:
mark('invalid statement', 36)
x = None
return x
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 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 typ(l):
"""
Parses
type(l) = ident «write(ident)» |
"array" «writeln; write((l + 1) * indent + 'array ')» "[" «write('[')» expression ".." «write(' .. ')» expression "]" «write(']')» "of" «write(' of ')» type(l)|
"record" «writeln; write((l + 1) * indent + 'record')» typedIds(l) {";" «write(';')» typedIds(l)} "end" «writeln; write((l + 1) * indent + 'end')».
Returns a type descriptor
"""
if SC.sym not in FIRSTTYPE:
getSym()
mark("type expected")
while SC.sym not in FIRSTTYPE | STRONGSYMS | FOLLOWTYPE:
getSym()
if SC.sym == IDENT:
write(SC.val)
ident = SC.val
x = find(ident)
getSym()
if type(x) == Type: x = Type(x.tp)
else:
mark('not a type')
x = Type(None)
elif SC.sym == ARRAY:
writeln()
write((l + 1) * indent + 'array ')
getSym()
if SC.sym == LBRAK:
write('[')
getSym()
else:
mark("'[' expected")
x = expression()
if SC.sym == PERIOD:
write(' .')
getSym()
else:
mark("'.' expected")
if SC.sym == PERIOD:
write('. ')
getSym()
else:
mark("'.' expected")
y = expression()
if SC.sym == RBRAK:
write(']')
getSym()
else:
mark("']' expected")
if SC.sym == OF:
write(' of ')
getSym()
else:
mark("'of' expected")
z = typ(l + 1).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)))
elif SC.sym == RECORD:
writeln()
write((l + 1) * indent + 'record ')
writeln()
write((l + 2) * indent)
getSym()
openScope()
typedIds(Var, l + 2)
while SC.sym == SEMICOLON:
write(';')
writeln()
write((l + 2) * indent)
getSym()
typedIds(Var, l + 2)
if SC.sym == END:
writeln()
write((l + 1) * indent + 'end')
getSym()
else:
mark("'end' expected")
r = topScope()
closeScope()
x = Type(CG.genRec(Record(r)))
else:
x = Type(None)
return x
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 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