Re:Why Lisp?
by btilly on Thursday May 07, 2015 @06:22PM
(#9508761)
Yes, except more reliable.
The fundamental unit of Lisp is expressions of the form (FOO ...). There are three basic cases.
1. FOO is one of a finite list of special forms. Those are the irreducible base of that language.
2. FOO is a function. In which case the ... is evaluated as Lisp (possibly including doing things like expand out other functions) before being passed to that function.
3. FOO is a macro. In which case the ... bit is turned into a list of things, but NOT evaluated, passed to the macro to be rewritten, and then the result is turned into an expression that is then evaluated by the same rule.
This is not completely true. There is a preprocessing step called reader macros that can do things like turn `(this expression) into (QUOTE this expression) to save typing. But those are very sparingly used.
The fundamental unit of Lisp is expressions of the form (FOO ...). There are three basic cases.
1. FOO is one of a finite list of special forms. Those are the irreducible base of that language.
2. FOO is a function. In which case the ... is evaluated as Lisp (possibly including doing things like expand out other functions) before being passed to that function.
3. FOO is a macro. In which case the ... bit is turned into a list of things, but NOT evaluated, passed to the macro to be rewritten, and then the result is turned into an expression that is then evaluated by the same rule.
This is not completely true. There is a preprocessing step called reader macros that can do things like turn `(this expression) into (QUOTE this expression) to save typing. But those are very sparingly used.