[patch] avoid the use of default constructors in stl_algo.h

[Gunter Winkler]

Hello,

while trying to optimize a custom (random access) iterator I found that 
some implementations of STL algorithms rely on the presence of a 
default constructor [1]. This is IMO unnecessary, because all iterators 
used in algorithms like lower_bound are (modified) copies of the 
initial iterators. Thus only a copy constructor is needed. The attached 
patch replaces declarations like

_ForwardIterator __left;

...

__left = __first;

by

_ForwardIterator __left = __first;


[1] The STL documentation from SGI requires each iterator to have a 
valid default constructor. However, I found no rationale why. 
Additionally, I don't know any algorithm that uses an iterator which is 
not related to the arguments of the function.

The patch has no influence on the results of make check-c++ (SVN head). 

What do you think?

mfg
Gunter
-------------- next part --------------
A non-text attachment was scrubbed...
Name: stl_algo_avoid_default_constructor1.diff
Type: text/x-diff
Size: 4282 bytes
Desc: not available
URL: <http://gcc.gnu.org/pipermail/libstdc++/attachments/20070214/20ac02a6/attachment.bin>