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Not being a C/C++ programmer, I wonder why they postfix their variables with "underscore"? https://chromium-review.googlesource.com/c/chromium/src/+/1510080/13

Not being a C/C++ programmer, I wonder why they postfix their variables with "underscore"? https://chromium-review.googlesource.com/c/chromium/src/+/1510080/13/device/gamepad/gamepad_device_linux.cc https://chromium-review.googlesource.com/c/chromium/src/+/15... e.g: switch_pro_4, dualshock_ps4_, ... It does not happen for all variables, what is this convention? :o

olig15 8y ago
I think it's because they're member variables. It makes them clear they're not local to the method.
- Insanity 8y ago
  At a quick glance, that does seem to be a difference with the postfixed variables! Have not yet encountered something like that in the languages I've worked with. ^^
  - cmrdporcupine 8y ago
    Wait til you discover Hungarian notation?
    - Insanity 8y ago
      That one I actually did encounter somewhere in high school, when a lecturer used it in Visual Basic, for some reason. xD
cmrdporcupine 8y ago
Google C++ style guide. It's for instance variables on classes, to distinguish from local variables. https://google.github.io/styleguide/cppguide.html#Variable_Names https://google.github.io/styleguide/cppguide.html#Variable_N...
- joshvm 8y ago
  Is there a reason for not using 'this'? I assume the risk is that you might have a scope where both this->foo and foo are valid and it's unclear which is which. You have no ambiguitiy with this->foo_, and foo (and if you forget 'this', foo_ is still clear).
  - jcelerier 8y ago
    six characters to type vs 1 ?
    - joshvm 8y ago
      You can argue that either way. Seeing 'this' unambiguously implies instance variable. Otherwise you have to spot the underscore and be aware of the conventions in the codebase. A good IDE should highlight class variables vs locals, though. On the other hand code can get really messy with boilerplate like this everywhere, and I personally agree with you. Although I believe Google also promotes human-readable variables over less typing.
      - tokyodude 8y ago
        I actually think implicit "this" is a language wart. I think C++, C#, Java, Swift, etc.. would all be better languages if they required `this`. As it is, nearly every one of them ends up needing a per team naming convention to help make the code readable. int area(int width) { return width * height; } What is "height". Is it a global variable? variable in some outer scope? A member/property of the current object? Absolutely no idea.
  - amalcon 8y ago
    Rules like this are usually less about risk, and more about conveying information. If I see a variable ending in "_", I immediately know to look for its definition in the class rather than the local scope.
  - nolok 8y ago
    I assume it's because if a dev forgets a this somewhere as a caller/accessor, you now have two problems; whereas if they forget a _, it doesn't compile.

olig15 8y ago

I think it's because they're member variables. It makes them clear they're not local to the method.

Insanity 8y ago
At a quick glance, that does seem to be a difference with the postfixed variables! Have not yet encountered something like that in the languages I've worked with. ^^
- cmrdporcupine 8y ago
  Wait til you discover Hungarian notation?
  - Insanity 8y ago
    That one I actually did encounter somewhere in high school, when a lecturer used it in Visual Basic, for some reason. xD

cmrdporcupine 8y ago

Google C++ style guide. It's for instance variables on classes, to distinguish from local variables. https://google.github.io/styleguide/cppguide.html#Variable_Names https://google.github.io/styleguide/cppguide.html#Variable_N...

joshvm 8y ago
Is there a reason for not using 'this'? I assume the risk is that you might have a scope where both this->foo and foo are valid and it's unclear which is which. You have no ambiguitiy with this->foo_, and foo (and if you forget 'this', foo_ is still clear).
- jcelerier 8y ago
  six characters to type vs 1 ?
  - joshvm 8y ago
    You can argue that either way. Seeing 'this' unambiguously implies instance variable. Otherwise you have to spot the underscore and be aware of the conventions in the codebase. A good IDE should highlight class variables vs locals, though. On the other hand code can get really messy with boilerplate like this everywhere, and I personally agree with you. Although I believe Google also promotes human-readable variables over less typing.
    - tokyodude 8y ago
      I actually think implicit "this" is a language wart. I think C++, C#, Java, Swift, etc.. would all be better languages if they required `this`. As it is, nearly every one of them ends up needing a per team naming convention to help make the code readable. int area(int width) { return width * height; } What is "height". Is it a global variable? variable in some outer scope? A member/property of the current object? Absolutely no idea.
- amalcon 8y ago
  Rules like this are usually less about risk, and more about conveying information. If I see a variable ending in "_", I immediately know to look for its definition in the class rather than the local scope.
- nolok 8y ago
  I assume it's because if a dev forgets a this somewhere as a caller/accessor, you now have two problems; whereas if they forget a _, it doesn't compile.