Why exactly is eval evil?

Question

I know that Lisp and Scheme programmers usually say that eval should be avoided unless strictly necessary. I’ve seen the same recommendation for several program

Answer 1

"When should I use eval?" might be a better question.

The short answer is "when your program is intended to write another program at runtime, and then run it". Genetic programming is an example of a situation where it likely makes sense to use eval.