Bite sized posts are continuing. In this post we are implementing If keyword:
class Interpreter: # ... previous code ... def If(self,xs): _, cond, trueblock, falseblock = xs if self.eval(cond): if isinstance(trueblock[0],list): for x in trueblock: self.eval(x) else: self.eval(trueblock) else: if falseblock: if isinstance(falseblock[0],list): for x in falseblock: self.eval(x) else: self.eval(falseblock) code=[ ["If",True, # True block, 3 statements [["Print","answer is 42"], ["Print","that is 21*2"], ["Print","that is just an ordinary number"]], # False block ["Print","answer is something else"] ], ["Print",["Mul","-",42]], ["If",False, ["Print","answer is 42"], ["Print","answer is something else"] ] ] interpreter=Interpreter() interpreter.run(code) Output:
answer is 42 that is 21*2 that is just an ordinary number ------------------------------------------ answer is something else 
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