def Arglist(ig):
""" get a comma separated list of expressions"""
#doesn't consume terminating item
f = Expr(ig)
if f == exp.Unterm: return exp.Unterm
if pio.CurrentItem(ig) == CommaWord:
pio.NextItem(ig)
return pop.Cons(f,Arglist(ig))
return pop.List1(f)
def IfExpr(ig):
"""parse if expression"""
pio.NextItem(ig)
condition = Expr(ig)
if not Expect(exp.THENWord,ig): return ''
alt1 = Expr(ig)
if not Expect(exp.ELSEWord,ig): return ''
alt2 = Expr(ig)
if not Expect(exp.FIWord,ig): return ''
return exp.Operation3C(exp.IFWord,condition,alt1,alt2)
def Factor(g):
""" return next factor - smallest initial sub expression """
lex = pio.CurrentItem(g)
if lex == '': return ''
if lex == pop.QUOTEWord: return Word(g)
if lex == pop.IFWord: return IfExpr(g)
if lex == pop.VALOFWord: return Valof(g)
if lex == pop.LLISTPARENWord: return Listexpression(g)
if lex == pop.LSETPARENWord: return Setexpression(g)
if(exp.PrefixP(lex)): return Complete('',g); # prefix operator
if exp.NullfixP(lex): pio.NextItem(g);return exp.Operation0C(lex)
if(pop.NumP(lex) or pop.StringP(lex) or pop.ListP(lex)):
pio.NextItem(g);return exp.LiteralC(lex) #a literal
if lex in reservedwords: return ''
if(pio.IdentP(lex)):
pio.NextItem(g);
if pio.CurrentItem(g) == LparenWord: #function call
return Call(exp.VarC(lex),g)
return exp.VarC(lex)
if exp.NullfixP(lex): pio.NextItem(g);return Operation0C(lex)
if lex==LparenWord : return ParenExpr(g) #parenthesized expression
print('Expected factor, found')
pio.Dump5(g);print()
exit()
def Definition(ig):
""" pick up a definition """
lhs = Expr(ig)
if lhs == '': return ''
lex = pio.NextItem(ig)
if lex != exp.EQUALWord and lex != exp.ISWord:
pro.printf('Expected = or is')
print('Found '); pio.Dump5(ig)
print()
exit()
rhs = Expr(ig)
df = exp.DefinitionC(lhs,lex,rhs)
if not Expect(exp.SEMICOLONWord,ig):
return Interm(df)
return df
def Complete(e,ig):
# current item is an infix operator
# return longest initial subexpression
q = pio.NextItem(ig) # q is the infix operator
f = Factor(ig)
if f=='':
if e == '': return Operation1C(q,unterm)
return exp.Operation2C(q,e,exp.Unterm)
while pio.CurrentItem(ig) != '' and exp.InfixP(pio.CurrentItem(ig)) and YieldsP(q,pio.CurrentItem(ig)):
f = Complete(f,ig)
if e == '': return exp.Operation1C(q,f)
#if q == WVRWord or q==WHILEWord or q==SWVRWord: return exp.CallC(exp.VarC(q),exp.List2(e,f))
if q in definables:
defined.add(q)
return exp.CallC(exp.VarC(q),exp.List2(e,f))
return exp.Operation2C(q,e,f)
def Input(opds):
global warehouse, nextindex, endoffile, treg, sreg, ig
if treg < nextindex: #already read it in, should be in warehouse
tag = ('input', treg, (), sreg, 0)
if tag in warehouse:
age, val = warehouse[tag]
return val
assert False, 'lost input'
if endoffile: # reached the end of file, result is eod
return EODWord
tsave = treg
ssave = sreg
treg = nextindex #read in whole lines
sreg = 0
while True:
try:
buff = input()
except:
endoffile = True
nextindex = treg
treg = tsave
sreg = ssave
return EODWord
ig = pio.ItemGenStringC(buff)
while pio.CurrentItem(ig) != '':
tag = ('input', treg, (), sreg, 0)
warehouse[tag] = (0, pio.NextItem(ig))
sreg += 1
warehouse[('input', treg, (), sreg, 0)] = (0, EOSWord)
sreg = 0
treg += 1
if treg > tsave: break
treg = tsave
sreg = ssave
nextindex = treg + 1
tag = ('input', treg, (), sreg, 0)
age, val = warehouse[tag]
return val
def Expect(w,ig):
if pio.CurrentItem(ig) == w: pio.NextItem(ig); return True
prp.printf('Expected ');pio.WriteItemln(w)
print('Found '); pio.Dump5(ig)
print()
exit()
def Word(g):
pio.NextItem(g)
w = pio.NextItem(g)
Expect(pop.QUOTEWord,g)
return exp.LiteralC(w)
def Supers(s):
""" register a bunch of supers"""
ig = pio.ItemGenStringC(s)
sup = pop.WordName(pio.NextItem(ig))
while pio.CurrentItem(ig) != '':
super[pop.WordName(pio.NextItem(ig))] = sup
