[LLVMdev] RFC: variable names

[Hal Finkel]

----- Original Message -----
> From: "Chandler Carruth" <chandlerc at google.com>
> To: "Nick Kledzik" <kledzik at apple.com>
> Cc: "LLVM Developers Mailing List" <llvmdev at cs.uiuc.edu>
> Sent: Monday, October 13, 2014 5:19:31 PM
> Subject: Re: [LLVMdev] RFC: variable names
> 
> 
> 
> 
> 
> On Mon, Oct 13, 2014 at 3:04 PM, Nick Kledzik < kledzik at apple.com >
> wrote:
> 
> 
> 
> I’d like to discuss revising the LLVM coding conventions to change
> the naming of variables to start with a lowercase letter.
> 
> 
> Almost all of your negatives of the current conventions also apply to
> your proposed convention.
> 
> 
> Type names: CamelCase
> Function names: camelCase
> Variable names: ???
> 
> 
> If we name variables in camelCase then variable names and function
> names collide.
> 
> 
> If we are going to change how we name variables, I very much want
> them to not collide with either type names or function names. My
> suggestion would be "lower_case" names.

+1

 -Hal

> 
> 
> This also happens to be the vastly most common pattern across all C++
> coding styles and C-based language coding styles I have seen.
> 
> 
> 
> This should not be a discussion on the pain of such a transition, or
> how to get from here to there, but rather, if there is a better
> place to be.
> 
> My arguments for the change are:
> 
> 1. No other popular C++ coding style uses capitalized variable names.
> For instance here are other popular C++ conventions that use
> camelCase:
> 
> http://google-styleguide.googlecode.com/svn/trunk/cppguide.xml
> http://www.c-xx.com/ccc/ccc.php
> http://geosoft.no/development/cppstyle.html
> 
> And, of course, the all-lower-case conventions (e.g. C++ ARM) don’t
> capitalize variable names. In addition, all the common C derived
> languages don’t use capitalized variable names (e.g. Java, C#,
> Objective-C).
> 
> 
> 2. Ambiguity. Capitalizing type names is common across most C++
> conventions. But in LLVM variables are also capitalized which
> conflates types and variables. Starting variable names with a
> lowercase letter disambiguates variables from types. For instance,
> the following are ambiguous using LLVM’s conventions:
> 
> Xxx Yyy(Zzz); // function prototype or local object construction?
> Aaa(Bbb); // function call or cast?
> 
> 
> 3. Allows name re-use. Since types and variables are both nouns,
> using different capitalization allows you to use the same simple
> name for types and variables, for instance:
> 
> Stream stream;
> 
> 
> 4. Dubious history. Years ago the LLVM coding convention did not
> specify if variables were capitalized or not. Different contributors
> used different styles. Then in an effort to make the style more
> uniform, someone flipped a coin and updated the convention doc to
> say variables should be capitalized. I never saw any on-list
> discussion about this.
> 
> 
> 5. Momentum only. When I’ve talked with various contributors
> privately, I have found no one who says they likes capitalized
> variables. It seems like everyone thinks the conventions are carved
> in stone...
> 
> 
> My proposal is that we modify the LLVM Coding Conventions to have
> variable names start with a lowercase letter.
> 
> Index: CodingStandards.rst
> ===================================================================
> --- CodingStandards.rst (revision 219065)
> +++ CodingStandards.rst (working copy)
> @@ -1073,8 +1073,8 @@
> nouns and start with an upper-case letter (e.g. ``TextFileReader``).
> 
> * **Variable names** should be nouns (as they represent state). The
> name should
> - be camel case, and start with an upper case letter (e.g. ``Leader``
> or
> - ``Boats``).
> + be camel case, and start with a lower case letter (e.g. ``leader``
> or
> + ``boats``).
> 
> * **Function names** should be verb phrases (as they represent
> actions), and
> 
> 
> 
> 
> command-like function should be imperative. The name should be camel
> case,
> _______________________________________________
> LLVM Developers mailing list
> LLVMdev at cs.uiuc.edu http://llvm.cs.uiuc.edu
> http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev
> 
> 
> 
> _______________________________________________
> LLVM Developers mailing list
> LLVMdev at cs.uiuc.edu         http://llvm.cs.uiuc.edu
> http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev
> 

-- 
Hal Finkel
Assistant Computational Scientist
Leadership Computing Facility
Argonne National Laboratory