Hi there!

Aleix and I noticed that equal? has a lot higher overhead than eqv? on chars, which means using (ice-9 match) for chars was suboptimal. This patch fixes that.

With this patch, guile now turns (equal? #\b var) into (eqv? #\b var) and (equal? any-non-fixnum-number-literal var) into (eqv? any-non-fixnum-number-literal var). This fixes the (ice-9 match) problem, and means you can dispatch to equal? in macros and guile will just do the right thing is there are any literals.

There is one regression: it is not o(n). Currently the primitve expander is run once per call, which means a (equal? #\a b c d e) becomes (and (eqv? #\a b) (eqv? b c d e)) and that second call gets run through the primitive expander once again, which checks all the arguments again. The solution I see is to manually build the conditional code, or to just extend the old code, where only the comparisons directly involving the literal is optimized: (equal? a b #\c) -> (and (equal? a b) (eqv? b #\c)).

Any feedback is welcome.

-- 
  Linus Björnstam