New C++ features – lambdas

http://arne-mertz.de/2015/10/new-c-features-lambdas/

by ingve • 11 years ago

21 24 11 years ago

msie2• 11 years ago

This is slightly tangential...I was trying to learn how to debug rust code with gdb/lldb and ran into so many problems. Then just for kicks I wrote a little C++ program and used gdb - so much better :D . I just hope they get the rust debugging situation smoothed out someday but for now I won't be using it.

brinker• 11 years ago

Did you try using rust-gdb or rust-lldb? They're wrappers for gdb and lldb respectively that make working with Rust code a lot nicer. They ship with the Rust compiler.

msie2• 11 years ago

Yes. I couldn't single step through a simple program without delving into assembly code. Couldn't list the program. Breakpoints weren't working. I think part of the problem was working on OSX. I was reading some Rust issue related to the debug info generation. Although the issue was closed I think it's still a problem. Oh well.

xigency8• 11 years ago

This is entirely a personal opinion, and probably something I will be lambasted for, but any example using a lambda in C++ I find to be 10,000× worse than the functional equivalent.

The benefit of writing code in C or C++ is that it gives your programs structure, and without naming your predicates or organizing your program in a logical way, it's basically a soup of abstract symbols.

My 2¢.

Kudos to the author for explaining how to use them. I naïvely assumed that the keyword `lambda' was involved.

ska3• 11 years ago

  ...I find to be 10,000x worse than the functional equivalent.

ironic.

xigency8• 11 years ago

| Using a named function rather than an inline, anonymous function.

Would you prefer 'the procedural equivalent'? 'Named equivalent'?

evanpw• 11 years ago

I often prefer to use lambdas as (named) inline function definitions:

  auto lessGold = [](const Hero& h1, const Hero& h2)
  {
      return h1.inventory().gold() < h2.inventory().gold();
  };

  std::sort(heroes.begin(), heroes.end(), lessGold);

AnimalMuppet4• 11 years ago

Interesting. In C++, a variable can have global scope, file scope, class/object scope, or local scope. A function can have global scope, file scope, or class/object scope. This lets you create a function that has local scope.

lbrandy• 11 years ago

any example using a lambda in C++ I find to be 10,000× worse than the functional equivalent.
I naïvely assumed that the keyword `lambda' was involved.

I don't understand how this two sentences co-exist. If you are unfamiliar with the syntax, surely you can't have a well informed opinion on which usage, in practice, turns out better?

I am assuming "functional equivalent" means the old named functors of C++03. And yea, you are likely super alone on that opinion. I normally say lambdas in C++11 mostly-obsolete (at least as the default) a huge class of the old ways from functors to bind/placeholders and friends. I don't think I've ever heard someone pining for the ol' days on this one.

xigency8• 11 years ago

Super alone.

I don't generally use STL so I mean without language extensions. It's easy enough to implement these things with traditional function pointers.

santaclaus• 11 years ago

Can you really call lambdas new at this point? C++11 has been around for what, four years now?

arne_mertz• 11 years ago

Compared to 17 years of standardization and >30 years of C++ altogether, 4 years is relatively new. In addition, much of the blog is not so much targeted at up-to-date C++ connoisseurs, as it is targeted at the kind of programmers I worked with in the past: people that have been stuck with legacy C++ code and older compilers for decades. So my whole "new C++ features" category covers C++11 and beyond.

New C++ features – lambdas

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