Hello, Guilers When using type specific equality predicates in guile, I've noticed that they only test the type of an argument, if it has not already decided that the answer is false. Working my way through all the predicates given by the meta command ",a =\??$" we find
GNU Guile 2.0.0.147-e309f Copyright (C) 1995-2011 Free Software Foundation, Inc. Guile comes with ABSOLUTELY NO WARRANTY; for details type `,show w'. This program is free software, and you are welcome to redistribute it under certain conditions; type `,show c' for details. Enter `,help' for help. scheme@(guile-user)> (= 9 10 "foo") $1 = #f scheme@(guile-user)> (char-set<= char-set:letter char-set:digit "foo") $2 = #f scheme@(guile-user)> (char-set= char-set:letter char-set:digit "foo") $3 = #f scheme@(guile-user)> (string-ci>=? "bar" "foo" '(#\f #\o #\o)) $4 = #f scheme@(guile-user)> (string-ci<=? "foo" "bar" '(#\f #\o #\o)) $5 = #f scheme@(guile-user)> (string>=? "bar" "foo" '(f o o)) $6 = #f scheme@(guile-user)> (string<=? "foo" "bar" '(f o o)) $7 = #f scheme@(guile-user)> (string-ci=? "foo" "bar" '(f o o)) $8 = #f scheme@(guile-user)> (string=? "foo" "bar" '(f o o)) $9 = #f scheme@(guile-user)> (char-ci>=? #\b #\f "foo") $10 = #f scheme@(guile-user)> (char-ci<=? #\f #\b "foo") $11 = #f scheme@(guile-user)> (char-ci=? #\f #\b "foo") $12 = #f scheme@(guile-user)> (char>=? #\b #\f "foo") $13 = #f scheme@(guile-user)> (char<=? #\f #\b "foo") $14 = #f scheme@(guile-user)> (char=? #\f #\b "foo") $15 = #f scheme@(guile-user)> (>= 9 10 "foo") $16 = #f scheme@(guile-user)> (<= 10 9 "foo") $17 = #f ... and so on. I have not checked all of Guile's included modules, but I suspect this is the case for most of them (certainly it is true for boolean=? and symbol=? from (rnrs base) ). Certain predicates do not have this problem because their third argument is expected to be an integer (string-ci<=, string-ci>=, string=, string>=, string<=, string-ci=) and others are restricted to an arity of two (free-identifier=?, bound-identifier=?). I was not sure whether or not to report this, as the behaviour is VERY consistent and therefore, I thought, likely to have been a conscious design choice. If this is the case, you can ignore this, but it seems to me that the reason for having type specific equality predicates is because 1. I want the guarantee or 2. It could theoretically help the bytecode compiler give better code. This is similar to the situation with fixnum and flonum arithmetic functions. If it is not, then we have some low hanging fruit for wannabe guile contributors ;) Regards, Ian
