> |I discovered the "arity" function in the documentation.  What puzzles
> |me is the non-intuitive values returned by arity.  Why does a block
> |with one argument return -2, but a block with two arguments return 2?
> Try the REAL one argumented closure.
>   proc{|a,|...}.arity
> The one you've tried was EMULATED one argumented closure.

[[1],[2],[3],[4]].collect{|x |x} #=> [[1], [2], [3], [4]]
[[1],[2],[3],[4]].collect{|x,|x} #=> [ 1 ,  2 ,  3 ,  4 ]

I did not know that. I don't think it's obvious from the word "emulated".

I have ruby-man-1.4 and .arity is not documented.

The documentation is not in CVS and I don't know where to get the latest.
This could be a good topic for the FAQ.

def foo(&proc) yield( 1 )     end; foo {|x,y|[x,y]}   #=> [1, nil]
def foo(&proc) yield([1])     end; foo {|x,y|[x,y]}   #=> [1, nil]
def foo(&proc) yield [1]      end; foo {|x,y|[x,y]}   #=> nil

The docs say using yield is much like using multiple assignment...

a = [1]   #=> [1]
a         #=> [1]
a,= [1]   #=> [1]
a         #=>  1

I see now... (i guess this has been discussed previously on this list?)

>       yield `(' [expr [`,' expr...]])

there's a `)' missing in the docs



matju