[Python-Dev] any support for a methodcaller HOF?

Ben.Young at risk.sungard.com Ben.Young at risk.sungard.com
Fri Feb 3 11:15:54 CET 2006

Michael Hudson wrote on 03/02/2006 09:36:30:

> Hmm.
> >>> funcTakingCallback(lamda x:x.method(zip, zop))
> >>> funcTakingCallback(methodcaller("method", zip, zop))
> I'm not sure which of these is clearer really.  Are lambdas so bad?
> (FWIW, I haven't internalized itemgetter/attrgetter yet and still tend
> to use lambdas instead those too).
> A class I wrote (and lost) ages ago was a "placeholder" class, so if
> 'X' was an instance of this class, "X + 1" was roughly equivalent to
> "lambda x:x+1" and "X.method(zip, zop)" was roughly equivalent to your
> "methodcaller("method", zip, zop)".  I threw it away when listcomps
> got implemented.  Not sure why I mention it now, something about your
> post made me think of it...

The C++ library Boost makes use of this method, but has a number of 
"placeholder" variables _1, _2, _3 ... _9 which can be combined to form 
expressions. e.g _1 + _2 is the same as lambda x,y: x+y so maybe there 
could be a lambda module that exposes placeholders like this. Pythons ones 
will be better that the C++ ones because we would be able to delay 
function calls as above with a much nicer syntax than the C++ versions. 

_1.method(_2+_3) !


> Cheers,
> mwh
> -- 
>   If you give someone Fortran, he has Fortran.
>   If you give someone Lisp, he has any language he pleases.
>     -- Guy L. Steele Jr, quoted by David Rush in comp.lang.scheme.scsh
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