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 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 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 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([], [Var(Int)]))
newDecl('write', StdProc([Var(Int)], []))
newDecl('writeln', StdProc([], []))
CG.genProgStart()
declarations(CG.genGlobalVars)
if SC.sym == PROGRAM: getSym()
else: mark("'program' expected")
ident = SC.val
if SC.sym == IDENT: getSym()
else: mark('program name expected')
openScope(); CG.genProgEntry(ident); x = body(ident, 0)
closeScope(); x = CG.genProgExit(x)
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 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():
"""
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 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 declarations(allocVar, l):
"""
Parses
declarations(l) =
{"const" «writeln; write(l * indent + 'const')» ident «writeln; write((l + 1) * indent + ident)» "=" «write(' = ')» expression ";" «write(';')»}
{"type" «writeln; write(l * indent + 'type')» ident «writeln; write((l + 1) * indent + ident)» "=" «write(' = ')» type(l + 1) ";" «write(';')»}
{"var" «writeln; write(l * indent + 'var')» «writeln; write((l + 1) * indent)» typedIds(l + 1) ";" «write(';')»}
{"procedure" «writeln; write(l * indent + 'procedure ')» ident «write(ident)» ["(" «write('(')» [["var" «write('var ')»] typedIds(l) {";" «write('; ')» ["var" «write('var ')»] typedIds(l)}] ")" «write(')')»] ";" «write(";")»
declarations(l + 1) compoundStatement(l + 1) ";"}.
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("'begin' or declaration expected")
while SC.sym not in FIRSTDECL | STRONGSYMS | FOLLOWDECL:
getSym()
while SC.sym == CONST:
writeln()
write(l * indent + 'const')
getSym()
if SC.sym == IDENT:
writeln()
write((l + 1) * indent + SC.val)
ident = SC.val
getSym()
if SC.sym == EQ:
write(' = ')
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:
write(';')
getSym()
else:
mark("; expected")
while SC.sym == TYPE:
writeln()
write(l * indent + 'type')
getSym()
if SC.sym == IDENT:
writeln()
write((l + 1) * indent + ident)
ident = SC.val
getSym()
if SC.sym == EQ:
write(' = ')
getSym()
else:
mark("= expected")
x = typ(l + 1)
newObj(ident, x) # x is of type ST.Type
if SC.sym == SEMICOLON:
write(';')
getSym()
else:
mark("; expected")
else:
mark("type name expected")
start = len(topScope())
while SC.sym == VAR:
writeln()
write(l * indent + 'var')
getSym()
writeln()
write((l + 1) * indent)
typedIds(Var, l + 1)
if SC.sym == SEMICOLON:
write(';')
getSym()
else:
mark("; expected")
varsize = allocVar(topScope(), start)
while SC.sym == PROCEDURE:
writeln()
write(l * indent + 'procedure ')
getSym()
if SC.sym == IDENT:
write(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('(')
getSym()
if SC.sym in {VAR, IDENT}:
if SC.sym == VAR:
write('var ')
getSym()
typedIds(Ref, l)
else:
typedIds(Var, l)
while SC.sym == SEMICOLON:
write('; ')
getSym()
if SC.sym == VAR:
write('var ')
getSym()
typedIds(Ref, l)
else:
typedIds(Var, l)
else:
mark("formal parameters expected")
fp = topScope()
sc[-1].par = fp[:] # procedure parameters updated
if SC.sym == RPAREN:
write(')')
getSym()
else:
mark(") expected")
else:
fp = []
parsize = CG.genFormalParams(fp)
if SC.sym == SEMICOLON:
write(';')
getSym()
else:
mark("; expected")
localsize = declarations(CG.genLocalVars, l + 1)
CG.genProcEntry(ident, parsize, localsize)
x = compoundStatement(l + 1)
CG.genProcExit(x, parsize, localsize)
closeScope() # scope for parameters and body closed
if SC.sym == SEMICOLON:
write(';')
getSym()
else:
mark("; expected")
return varsize
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 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", 50)
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", 51)
x = expression()
if type(x) == Const: newObj(ident, x)
else: mark('expression not constant', 52)
else: mark("constant name expected", 53)
if SC.sym == SEMICOLON: getSym()
else: mark("; expected", 54)
while SC.sym == TYPE:
getSym()
if SC.sym == IDENT:
ident = SC.val
getSym()
if SC.sym == EQ: getSym()
else: mark("= expected", 55)
x = typ()
newObj(ident, x) # x is of type ST.Type
if SC.sym == SEMICOLON: getSym()
else: mark("; expected", 56)
else:
mark("type name expected", 57)
start = len(topScope())
while SC.sym == VAR:
getSym()
typedIds(Var)
if SC.sym == SEMICOLON: getSym()
else: mark("; expected", 58)
varsize = allocVar(topScope(), start)
while SC.sym == PROCEDURE:
getSym()
if SC.sym == IDENT: getSym()
else: mark("procedure name expected", 59)
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", 60)
fp = topScope()
sc[-1].par = fp[:] # procedure parameters updated
if SC.sym == RPAREN: getSym()
else: mark(") expected", 61)
else: fp = []
parsize = genFormalParams(fp)
if SC.sym == SEMICOLON: getSym()
else: mark("; expected", 62)
# PROCEDURE CALL
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", 63)
return varsize
