On Mon, Sep 28, 2009 at 5:23 AM, Jarkko Oranen <chous...@gmail.com> wrote:
> What happens is, when you call (mfloat + 1 2) the macro evaluates ('+
> (float 1) (float 2)), ie. it calls the *symbol* + with parameters 1.0
> and 2.0. Symbols, when used as functions, look themselves up in
> whatever associative thing you give them as the first parameter, OR
> return the second parameter in case of lookup failure. So, ('+ 1.0
> 2.0) evaluates to 2.0, which is the macro expansion. and as 2.0
> evaluated is 2.0, it is the actual result.
Very sneaky. Why is invoking a symbol returning the second argument even
when the first is not an associative thing at all? It should probably return
the second argument (defaulting to nil) on not-found but not on genuine
errors. A ClassCastException java.lang.Float cannot be cast to
clojure.core.IAssoc (or whatever) would have been more informative in this
case.
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