Andy Little wrote:
"Peter Dimov" wrote
What I really want is this:
void foo( myvec& v, const myset& s, int a ) { // ...
inline bool f( int x ) { return std::abs( x ) < a && s.find( x ) != s.end(); }
v.erase( std::remove_if( v.begin(), v.end(), f ), v.end() ); }
for obvious readability reasons. This syntax also allows me to use a more descriptive name instead of f, and the consistency with ordinary function definitions will make it easier to teach. It may be somewhat easier to parse or specify, but I haven't considered this in detail.
Its interesting that you bring up the teaching issue AFAIK. Robert Rameys earlier point regarding the benefits of what seems to just be a "cool" feature to C++ is apt . Do local functions, named or unnamed really add that much to the language?. They do certainly add another layer of complexity to the parser and whats more important another layer of complexity that students will feel that they must learn and use.
Yes, local functions do add to the language. What you currently need is: static bool f( int x, int a, myset const & s ) { return abs( x ) < a && s.find( x ) != s.end(); } void foo( myvec& v, const myset& s, int a ) { // ... v.erase( std::remove_if( v.begin(), v.end(), std::bind( f, _1, a, std::ref( s ) ) ), v.end() ); } As you can see, there is an additional bind needed to pass the arguments from the enclosing context to f, but the more important thing is that f needs to be defined outside of foo, removed from the point of use. A local function decreases complexity, and it's much easier to grasp because it's just like an ordinary function, only defined inside of foo.
C++'s main problem is that it doesnt have enough standard libraries to compete with (say) Java. Two obvious ones still not on the horizon are Unicode and GUI. ( I am going to try to do something about the GUI, though there must be much greater GUI experts than me that could do a better job). A major reason given by the committee AFAICS (in GUI case) was that the committee doesnt have enough time to deal with it. Yet there seems to be adequate time to discuss the addition of more complexities to the language itself. A great language missing some essential standard libraries. Will that be C++ epitaph?
This is a pretty common view, but C++ has been missing essential standard libraries for more than ten years, and it still competes with Java. C++ simply doesn't play by the marketing rule that whoever has the more checkboxes wins. It doesn't even have garbage collection! An automatic loss, you'd think. Not only that; what standard libraries C++ does have are often simply not used (iostreams, locale.)