Re: [boost] painless currying

Subject: Re: [boost] painless currying
From: Eric Niebler (eric_at_[hidden])
Date: 2011-08-26 14:58:57

On 8/26/2011 2:05 PM, Dave Abrahams wrote:
>> Eric Niebler wrote:
>>> I don't see any technical obstacles to:
>>>
>>> f(_, y, z)
>>>
>>> where _ is a placeholder. You could use positional placeholders for
>>> argument reordering.
> 
> That's more general than straight currying, and it's clearer: f(x,_,_)
> is a curried version of f that is a bit more explicit about what it
> means than just writing f(x).
> 
>> You might say the syntactic advantages of this over bind(f, _, y, z) are
>> minimal. You might be right.
> 
> I wouldn't say that.  I like the placeholder syntax; it's similar to
> what MPL does, and frankly I had assumed we already had libraries
> (phoenix?) that did things this way.  

All the library solutions we have so far involve an explicit call to a
function named "bind" or similar.

> The only question is what happens
> when you write f(x,y,z).  IIUC, phoenix leaves you with a nullary
> function, but you're proposing to actually call f.  I'm just not sure
> that's quite as appropriate in C++ as it is in Haskell.  Suppose you
> *wanted* a nullary function object (e.g. so you could launch a thread
> with it) rather than its result.  Then you need to switch to a different
> syntax for the final argument?

Ah, thank you. Good point. I think I'll let this issue drop now.

-- 
Eric Niebler
BoostPro Computing
http://www.boostpro.com