On Thursday, 12 July 2012 at 13:19:00 UTC, Thiez wrote:
It's already quite obvious that the compiler does not obey its
own rewrite rules (see
http://dlang.org/operatoroverloading.html#compare) Consider
opCmp:
a < b
is rewritten to
a.opCmp(b) < 0
or
b.opCmp(a) > 0
Let's assume the first rule is always chosen. According to the
very rewrite rule we just applied, this must be rewritten to
a.opCmp(b).opCmp(0) < 0
which must be rewritten to
a.opCmp(b).opCmp(0).opCmp(0) < 0
and then
a.opCmp(b).opCmp(0).opCmp(0).opCmp(0) < 0
and so on, to infinity.
It seems quite obvious the compiler does not rewrite compares
on integers or all hell would break loose... The language
reference should be more specific about these things.
Quote from 'The D Programming Language' chapter 12.1:
"D’s approach to operator overloading is simple: whenever at
least one participant in an operator expression is of
user-defined type, the compiler rewrites the expression into a
regular method call with a specific name. Then the regular
language rules apply."
So, assuming opCmp returns integer, then a.opCmp(b) < 0 doesn't
get rewritten (lowered) any further, because user-defined types
are not involved.
