From: gwtmp01@...
Date: 2007-02-06T08:20:49+09:00
Subject: Re: Proc vs lambda vs proc


On Feb 5, 2007, at 4:28 PM, Brian Candler wrote:
> Now, I wonder why you couldn't approach this problem from the other
> direction: instead of having two or more different types of lambda,  
> which
> handle 'return' semantics differently, have a single type of lambda  
> and two
> different return statements. For example:
>
>    return val     # return from enclosing method
>    result val     # return from this block only

I think Ruby already has this via 'break'.  Also, the default behavior
of returning the last expression evaluated in a block is an implicit
'break' in Proc.new procs.

Sometimes you want a Proc to behave like the body of a method (the  
lambda flavor of procs) and sometimes you want it to behave like the  
body of
an iterator (the Proc.new flavor of procs).

> That is, use the same argument list handling for a 'def' method  
> definition,
> a block, and a Proc/proc/lambda.

That seems to be a goal of the 1.9/2.0 line of Ruby as part of  
'cleaning up'
the semantics of block argument scope.

I wish there was some better terminology for the two different types
of procs (rather than 'lambda type' and 'Proc.new type').  I think  
Pickaxe
uses 'raw proc' but I can never remember which type of proc is being
referenced by that phrase.


Gary Wright