Re: [boost] [function types][review] (repost with new formatting)

From: Tobias Schwinger (tschwinger_at_[hidden])
Date: 2005-06-19 06:09:16

David Abrahams wrote:
> Tobias Schwinger <tschwinger_at_[hidden]> writes:
> 
> 
>>David Abrahams wrote:
>>
>>>[...]   1. Proof it
>>
>>It has been applied to Boost.Lambda and to boost:mem_fn (which is a part of Bind).
>>
>>I'll attach the results to the end of this post. An archive containing the 
>>results, all refactored code and a diff for Boost.Lambda (to easily spot the 
>>changes) has been uploaded to the vault:
>>
>>    http://tinyurl.com/c3tpv
> 
> 
> Can you say a little something to help me understand the wc numbers
> you give at the end of your post?
> 

Sure. Sorry for the too brief summary. It was late in my timezone and I had to 
get some sleep.

'wc' is a Unix shell command and stands for "word count" (I'm pretty sure you 
know that - but some readers might not). With the '-l' it counts the number of 
lines in (a) file(s).

Since you requested to find out the portential of Function Types to eliminate 
existing/redundant Boost code, the output of the 'wc' command was meant to 
document ammount of factored out code.

--- Function template boost::mem_fn (lives in the directory of Boost.Bind)

The original uses files with different versions of templates for arity 0-9 and 
macros in them. These are repetetively included with different macro definitions 
to generate variations for different calling conventions and with or without 
'return' (if BOOST_NO_VOID_RETURNS is set).

The changed version does not need these variations. And because it's tedious too 
do everything ten times, I used Boost.Preprocessor to help me with it (for the 
arity part).
For counting lines, however, I used an already-preprocessed version of this file 
(because we want to measure Function Types and not Boost.Preprocessor).

Without BOOST_NO_VOID_RETURNS and only the default calling convention we end up 
with 936 lines less (the original version needs 1561 lines total - my version 
needs 625 -- actually 325 but this would be "unfair" because of using 
Boost.Preprocessor).

The footnotes indicate how the preprocessed size of the library scales up, when 
certain features or workarounds are enabled.

--- The Function Types library applied to Boost.Lambda:

There are 464 lines less in the Lambda library.

It can theoretically take advantage of the common configuration - in practice 
Type Traits still keeps it from working with any calling convention.

This file contains the code for handling member pointers:
changed     358 lines in lambda/detail/member_ptr.hpp
original    737 lines in lambda.bak/detail/member_ptr.hpp

This file contains the functor frontend for lambda functors, data members and 
functions:

changed     519 lines in lambda/detail/function_adaptors.hpp
original    640 lines in lambda.bak/detail/function_adaptors.hpp

A wrapper for 'function_type_class' (to decorate cv-qualification) has been put 
here. This will not be needed anymore with the next version of Function Types:
changed     556 lambda/detail/lambda_traits.hpp
original    527 lambda.bak/detail/lambda_traits.hpp

See the diff file included in the archive for details (it's too large to post it 
here).

Hope this works. Please ask if something is unclear.

Regards,

Tobias