Question

What would be an example of an anaphoric conditional in Lisp? Please explain the code as well.

Answer 1

An example is the Common Lisp LOOP:

(loop for item in list
      when (general-predicate item)
      collect it)

The variable IT has the value of the test expression. This is a feature of the ANSI Common Lisp LOOP facility.

Example:

(loop for s in '("sin" "Sin" "SIN")
      when (find-symbol s)
      collect it)

returns

 (SIN)

because only "SIN" is a name for an existing symbol, here the symbol SIN. In Common Lisp symbol names have internally uppercase names by default.