evaluation.md

Evaluation

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Add a method def eval(self, variables) to every AST node and recursively call eval until you reach the terminal leaves.

For now we will disregard all runtime errors.

Value

classValue(AST):
...
defeval(self, variables):
returnself.value

Variable

classVariable(AST):
...
defeval(self, variables):
returnvariables[self.name]

FuncCall

classFuncCall(AST):
...
defeval(self, variables):
args= [arg.eval(variables) forarginself.args]
returnvariables[self.name](args)

BinaryOp

classBinaryOp(AST):
...
defeval(self, variables):
left=self.left.eval(variables)
right=self.right.eval(variables)
ifself.op=='+':
returnleft+rightifself.op=='-':
returnleft-rightifself.op=='*':
returnleft*rightifself.op=='/':
returnleft/rightifself.op=='%':
returnleft%right

UnaryOp

classUnaryOp(AST):
...
defeval(self, variables):
item=self.item.eval(variables)
ifself.op=='+':
return+item# redundant, but ey why notifself.op=='-':
return-item

And we are done!

%>py main.py
2.2704074859237844

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