What kind of prefix do you use for member variables?

No doubt, it's essential for understanding code to give member variables a prefix so that they can easily be distinguished from "normal" variables.

But what kind of prefix do you use?

I have been working on projects where we used m_ as prefix, on other projects we used an underscore only (which I personally don't like, because an underscore only is not demonstrative enough).

On another project we used a long prefix form, that also included the variable type. mul_ for example is the prefix of a member variable of type unsigned long.

Now let me know what kind of prefix you use (and please give a reason for it).

EDIT: Most of you seem to code without special prefixes for member variables! Does this depend on the language? From my experience, C++ code tends to use an underscore or m_ as a prefix for member variables. What about other languages?

Solution 1:

No doubt, it's essential for understanding code to give member variables a prefix so that they can easily be distinguished from "normal" variables.

I dispute this claim. It's not the least bit necessary if you have half-decent syntax highlighting. A good IDE can let you write your code in readable English, and can show you the type and scope of a symbol other ways. Eclipse does a good job by highlighting declarations and uses of a symbol when the insertion point is on one of them.

Edit, thanks slim: A good syntax highlighter like Eclipse will also let you use bold or italic text, or change fonts altogether. For instance, I like italics for static things.

Another edit: Think of it this way; the type and scope of a variable are secondary information. It should be available and easy to find out, but not shouted at you. If you use prefixes like m_ or types like LPCSTR, that becomes noise, when you just want to read the primary information – the intent of the code.

Third edit: This applies regardless of language.

Solution 2:

I do not use any prefix at all. If I run into danger of mixing up local variables or method parameters with class members, then either the method or the class is too long and benefits from splitting up.

This (arguably) not only makes the code more readable and somewhat "fluent", but most importantly encourages well structured classes and methods. In the end, it thus boils down to a completely different issue than the prefix or no-prefix dillema.

UPDATE: well, taste and preferences change, don't they.. I now use underscore as the prefix for member variables as it has proven to be beneficial in recognizing local and member variables in the long run. Especially new team members sometimes have hard time when the two are not easily recognizable.

Solution 3:

None. I used to use underscore, but was talked out of it on a project where the others didn't like it, and haven't missed it. A decent IDE or a decent memory will tell you what's a member variable and what isn't. One of the developers on our project insists on putting "this." in front of every member variable, and we humour him when we're working on areas of code that are nominally "his".

Solution 4:

Underscore only.

In my case, I use it because that's what the coding standards document says at my workplace. However, I cannot see the point of adding m_ or some horrible Hungarian thing at the beginning of the variable. The minimalist 'underscore only' keeps it readable.