def Factor():
token = Tokenizer.PeakToken()
if token.IsVariable():
Tokenizer.Consume()
return ConstantFunction(Token.Variable.get_var(token.text))
elif token.IsSymbol('('):
Tokenizer.Consume()
parseTree = Expression()
EndParens()
return parseTree
elif token.IsNumber() or \
token.IsSymbol(['+','-']):
return Number()
elif token.IsFunc():
Tokenizer.Consume()
parseTree = UnaryFunction(token.text)
parseTree.child(Factor())
return parseTree
else:
raise ValueError("Factor")
def FactorTail(leftParseTree):
token = Tokenizer.PeakToken()
if token.IsSymbol(['*','/','^']):
Tokenizer.Consume()
parseTree = BinaryFunction(token.text)
parseTree.lchild(leftParseTree)
parseTree.rchild(Factor())
return FactorTail(parseTree)
elif token.IsFunc():
# implicit multiply
Tokenizer.Consume()
parseTree = BinaryFunction('*')
rightParseTree = UnaryFunction(token.text)
rightParseTree.child(Factor())
parseTree.lchild(leftParseTree)
parseTree.rchild(rightParseTree)
return FactorTail(parseTree)
elif token.IsEOF() or \
token.IsSymbol(['+','-',')']):
return leftParseTree
else:
raise ValueError("Factor Tail")
def Number():
token = Tokenizer.PeakToken()
negate = token.IsSymbol(['-'])
if token.IsSymbol(['+','-']):
# ignore unary +
# use negate for unary -
Tokenizer.Consume()
token = Tokenizer.PeakToken()
if token.IsNumber():
Tokenizer.Consume()
text = ('-' if negate else '') + token.text
val = float(text) if '.' in text else int(text)
return ConstantFunction(val)
else:
raise ValueError("Invalid Number")
def TermTail(leftParseTree):
token = Tokenizer.PeakToken()
if token.IsSymbol(['+','-']):
Tokenizer.Consume()
parseTree = BinaryFunction(token.text)
parseTree.lchild(leftParseTree)
parseTree.rchild(Term())
return TermTail(parseTree)
elif token.IsEOF() or \
token.IsSymbol(')'):
return leftParseTree
else:
raise ValueError("Term Tail")
def EndParens():
token = Tokenizer.PeakToken()
if token.IsSymbol(')'):
Tokenizer.Consume()
else:
raise ValueError("Unmatched parenthesis")
