On Sat, Feb 26, 2011 at 8:14 PM, Mark <markaddle...@gmail.com> wrote:
> I get this:
> #<CompilerException java.lang.IllegalArgumentException: Wrong number
> of args (3) passed to: Symbol (C:\Users\addma03\workspace\test\src\main
> \clojure:1)>
>
> A few suggestions:
> 1) An improved line number
> 2) I'd like to see the value of the Symbol
> 3) I'd like to see the three args applies to the symbol and, if the
> symbol resolves to a function, I'd like to see the arity of the
> function.
>
> Something like:
> Wrong number of args (3) passed to Symbol 'some-fn' which expects
> arity 2
This is interesting. I just checked with my copy of 1.2 and it seems
you can indeed call a symbol as a function. It appears to try to look
itself up in its first argument, the same as a keyword, and if not
found or the first argument is not a map returns the (optional) second
argument:
user=> ('+ {'+ 3 '* 4} 42)
3
user=> ('+ {'- 3 '* 4} 42)
42
Of course this is rather icky to use because of the need to quote the symbols.
So, the arity expected by a function like + ends up irrelevant. If you
invoke something on '+ it wants either one or two arguments.
If you're seeing this error you probably have a buggy macro that's not
unquoting something as many times as it should be. Quoting-depth
errors (other than forgetting to unquote something at all) seem to be
most common when writing macros that emit other macros, and ending up
with nested syntax-quoted expressions, doubled-up ~~@foo type
unquotings, and things like `(quote ~foo) in helper functions.
If the error points to a macro invocation I'd suggest inspecting the
output of (macroexpand-1 '(the-problem-invocation)) and seeing what
you get. If the output contains quoted symbols in operator position
that clearly are meant to be just normal calls to functions then
you've at least determined that the problem is caused by the macro.
Though it could be the case that your arguments to the macro violate
its preconditions. If it's not your own macro, check its
documentation. If it is it has a bug since it's not doing what you
want it to do and it's yours. If it's not it may or may not have a
bug.
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