Added optimization opportunity #25: improved type-based optimization

of EQL forms.

diff --git a/OPTIMIZATIONS b/OPTIMIZATIONS
index 5474bd2..50d3417 100644 (file)
--- a/OPTIMIZATIONS
+++ b/OPTIMIZATIONS
@@ -203,3 +203,17 @@ Python does not know that &REST lists are LISTs (and cannot derive it).
 a. Iterations on &REST lists, returning them as VALUES could be
    rewritten with &MORE vectors.
 b. Implement local unknown-values mv-call (useful for fast type checking).
+--------------------------------------------------------------------------------
+#25
+EQL is implemented generically in situations where this isn't necessary.
+
+(defun f (x y)
+  (declare (type (or symbol fixnum) x)
+          (optimize speed (safety 0) (debug 0)))
+  (eql x y))
+
+SUBTYPEP is smart enough to determine that this type is a subtype
+of (and (or (not number) fixnum) (not character))
+
+This sitation where the type is (OR NULL FIXNUM) comes up
+in cl-bench, for example in the value returned by POSITION.