# 2 Names¶

Good names are essential to sound software design. This section contains guidelines for naming files, types, functions, class members, variables, etc. The main goal is to use clear and unambiguous names. Also, we want naming conventions for different entities so that, when applied, the role of each is obvious from the form of its name.

## Good names are clear and meaningful¶

2.1 Every name must be meaningful. In particular, its meaning must be clear to other code developers and users, not just the author of the name.

A substantial benefit of good name selection is that it can greatly reduce the amount of developer debate to define a concept. A good name also tends to reduce the amount of documentation required for others to understand it. For example, when the name of a function clearly indicates what it does and the meaning and purpose of each argument is clear from its name, then code comments may be unnecessary. Documentation can be a substantial part of software and requires maintenance. Minimizing the amount of required documentation reduces this burden.

## Avoid cryptic names¶

2.2 Tersely abbreviated or cryptic names should be avoided. However, common acronyms and jargon that are well understood by team members and users may be used.

## Use terminology consistently¶

2.3 Terminology must be used consistently; i.e., for names and concepts in the code and in documentation. Multiple terms should not be used to refer to the same concept and a concept should not be referred to by multiple terms.

Using a clear, limited set of terminology in a software project helps maintain the consistency and integrity of the software, and it makes the code easier to understand for developers and users.

2.4 Each name must be consistent with other similar names in the code.

For example, if getter/setter methods follow the convention “getFoo” and “setFoo” respectively, then adding a new setter method called “putBar” is clearly inconsistent.

## Name directories so it’s easy to know what’s in them¶

2.5 Each directory must be named so that the collective purpose of the files it contains is clear. All directory names should follow the same style conventions.

All directory names should use all lower case letters and consist of a single word in most cases. A directory name with more than one word should use an ‘underscore’ to separate words.

For example, use:

cool_stuff


not

cool-stuff


2.6 C++ header and source file extensions must be: *.hpp and *.cpp, respectively.

2.7 C header and source files (e.g., tests, examples, and generated API code) must have extensions *.h and *.c, respectively.

2.8 Fortran source files (e.g., tests and examples, and generated API code) must have the extension *.f or *.F . *.F must be used if the preprocessor is needed to compile the source file.

## Associated source and header file names should match¶

2.9 The names of associated header and source files should match, apart from the file extension, to make their association clear.

For example, the header and source files for a class “Foo” should be named “Foo.hpp” and “Foo.cpp”, respectively.

Also, files that are closely related in other ways, such as a header file containing prototypes for a set of methods that are not class members and a source file containing implementations of those methods, should be named the same or sufficiently similar so that their relationship is clear.

## File contents should be clear from file name¶

2.10 The name of each file must clearly indicate its contents.

For example, the header and source file containing the definition and implementation of a major type, such as a class must include the type name of the type in the file name. For example, the header and implementation file for a class called “MyClass” should be named “MyClass.hpp” and “MyClass.cpp”, respectively.

Files that are not associated with a single type, but which contain closely related functionality or concepts, must be named so that the functionality or concepts are clear from the name. For example, files that define and implement methods that handle file I/O should be named “FileIO.hpp” and “FileUtils.cpp”, or similar.

## File names should not differ only by case¶

2.11 File names that differ only in letter case must not be used.

Since we must support Windows platforms, which have limited case sensitivity for file names, having files with names “MyClass.hpp” and “myclass.hpp”, for example, is not acceptable.

## Namespace name format¶

2.12 All namespaces defined must use all lowercase letters for consistency and to avoid user confusion.

## Type name format¶

2.13 Type names (i.e., classes, structs, typedefs, enums, etc.) must be nouns and should be in mixed case with each word starting with an upper case letter and all other letters in lower cases.

For example, these are preferred type names:

DataStore, MyCollection, TypeUtils


These type names should not be used:

dataStore, mycollection, TYPEUTILS


2.14 Separating characters, such as underscores, should not be used between words in a type name.

For example, these names are not preferred type names:

Data_store, My_Collection


Note

Exceptions to the guidelines above include cases where types play a similar role to those in common use elsewhere. For example, naming an iterator class “base_iterator” would be acceptable if it is conceptually similar with the C++ standard library class.

2.15 Suffixes that may be used by compilers for name mangling, or which are used in the C++ standard library, such as “_t”, must not be used in type names.

## Function name format¶

2.16 Function names must use “camelCase” or “pot_hole” style. camelCase is preferred.

camelCase style: The first word has all lower case letters. If multiple words are used, each word after the first starts with an upper case letter and all other letters in the word are lower case. Underscores must not be used in camelCase names, but numbers may be used.

For example, these are proper camelCase names:

getLength(), createView2()


pot_hole style: All letters are lower case. If multiple words are used, they are separated by a single underscore. Numbers may be used in pothole style names.

For example, these are acceptable pothole style variable names:

push_front(), push_back_2()


2.17 Names of related functions, such as methods for a class, should follow the same style.

Note

Exception: While consistency is important, name style may be mixed when it makes sense to do so. While camelCase style is preferred for class member functions, a class may also contain methods that follow pot_hole style if those methods perform operations that are similar to C++ standard library functions, for example.

For example, the following method names are acceptable for a class with camelCase style names:

push_back(), push_front()


if those methods are similar in behavior to C++ standard methods.

## Function names should indicate behavior¶

2.18 Each function name must indicate clearly indicate what the function does.

For example:

calculateDensity(), getDensity()


are good function names because they distinguish the fact that the first performs a calculation and the second returns a value. If a function were named:

density()


what it actually does is murky; i.e., folks would have to read its documentation or look at its implementation to see what it actually does.

2.19 Function names should begin with a verb because they perform an action.

2.20 Verbs such as “is”, “has”, “can”, etc. should be used for functions with a boolean return type.

For example, the following names are preferred:

isInitialized(), isAllocated()


## Data member and variable name format¶

2.22 All variables (class/struct members, function-scoped variables, function arguments, etc.) must use either “camelCase” style or “pot_hole” style. Pot_hole style is preferred since it distinguishes variable names from method names.

For example, these are acceptable variable names:

myAverage, person_name, pressure2


2.23 Non-static class and struct data member names must have the prefix “m_”.

This convention makes it obvious which variables are class members/struct fields and which are other local variables. For example, the following are acceptable names for class data members using camelCase style:

m_myAverage, m_personName


and acceptable pothole style:

m_my_average, m_person_name


2.24 Static class/struct data member names and static file scope variables must have the prefix “s_”.

Similar to the guideline above, this makes it obvious that the variable is static.

## Variable names should indicate type¶

2.25 Verbs, such as “is”, “has”, “can”, etc., should be used for boolean variables (i.e., either type bool or integer that indicates true/false).

For example, these names are preferred:

m_is_initialized, has_license


to these names:

m_initialized, license


2.26 A variable that refers to a non-fundamental type should give an indication of its type.

For example,:

Topic* my_topic;


is clearer than:

Topic* my_value;


## Macro and enumeration name format¶

2.27 Preprocessor macro constants must be named using all uppercase letters and underscores should be used between words.

For example, these are acceptable macro names:

MAX_ITERATIONS, READ_MODE


These are not acceptable:

maxiterations, readMode


2.28 The name of each enumeration value should start with a capital letter and use an underscore between words when multiple words are used.

For example,:

enum Orange
{
Navel,
Valencia,
Num_Orange_Types
};