Common Lisp Recipes: A Problem-Solution Approach

10. Evaluation, Compilation, Control Flow

To be honest, I couldn’t find a better title for this chapter. It’s kind of a hodgepodge of various subjects, although many of them would probably indeed fit into the chapter called Evaluation and Compilation in the COMMON LISP standard.

However, I think that specifically Recipes 10-8 and 10-9 deserve your attention as they provide fairly detailed treatments of topics which are rarely, if ever, covered in COMMON LISP books.

10-1. Comparing Arbitrary Lisp Objects

Problem

You’re confused by EQ, EQL, EQUAL, and EQUALP. Which one are you supposed to use when?

Solution

It is actually not as complicated as it seems. If you just need a few simple rules of thumb, here they are:

  I)    When comparing objects ...