On eval in dynamic languages generally and in Racket specifically (2011)

On eval in dynamic languages generally and in Racket specifically posted by Matthew Flatt The eval function is at the heart of a dynamic language, and it strikes many newcomers as an amazingly powerful tool. At the same time, experienced programmers avoid eval , because unnecessary use creates trouble. It’s not easy to explain why eval should be avoided or when it"s appropriate to use eval , but I’ll take another stab at it here. What is eval ? Consider the following “program” in English prose: Assume that your favorite color is red. Now imagine a balloon that is your favorite color. Paint a canvas the same color as the balloon. As English goes, that’s a fairly clear program with a fairly well-defined result. When I follow those instructions, at least, I will always produce a red canvas (assuming that I have a canvas and some red paint, but a potential lack of art supplies is not the point here). I would come up with a red canvas even if I read the instructions when surrounded b ... Read full article.