compiler: improve code for and/or.

Squeeze the constant and unreachable cases out of (and ...)
and (or ...) forms, producing a more streamlined translation.

This is the first appearance of structural pattern matching in
the compiler!

* share/txr/stdlib/compiler.tl (compiler compile): Handle and
using new expand-and function, which translates it to if
forms. Handle or via the renamed method comp-or.
(compiler comp-and-or): Renamed to comp-or, since it handles
only or. All the switching between or/and is eliminated.
The or form is first reduced using simplify-or.
We retain this function because one case in cond relies on or;
or is a useful primitive because (or a b) evaluates a only
once; whereas (if a a b) requires common-subexpression
elimination to generate the same code as (or a b).
(true-const-p, expand-and, flatten-or, reduce-or,
simplify-or): New functions.

0 files changed, 0 insertions, 0 deletions