C++ Practices

8/4/2019 C++ Practices

1/44

C++ Practices

Guidelines to improve readability

of code


2/44

Naming Conventions


3/44

Names representing types must be in

mixed case starting with upper case

Line, SavingsAccount


4/44

Variable names must be in mixed case

starting with lower case.

line, savingsAccount Makes variables easy to distinguish from

types, and effectively resolves potential

naming collision as in the declaration Line

line


5/44

Named constants (including enumerationvalues) must be all uppercase using underscoreto separate words

In general, the use of such constants should beminimized. In many cases implementing thevalue as a method is a better choice:

int getMaxIterations() // NOT: MAX_ITERATIONS = 25

{return 25;

}


6/44

Names representing methods or functionsmust be verbs and written in mixed casestarting with lower case

getName(), computeTotalWidth()

Common practice in the C++ developmentcommunity. This is identical to variable

names, but functions in C++ are alreadydistingushable from variables by theirspecific form


7/44

Abbreviations and acronyms must not be

uppercase when used as name

exportHtmlSource();//NOT: exportHTMLSource(); openDvdPlayer();//NOT: openDVDPlayer();


8/44

Global variables should always be referred

to using the :: operator

::mainWindow.open(),::applicationContext.getName()

In general, the use of global variables

should be avoided


9/44

Private class variables should have

underscore suffix

class SomeClass { private: int length_; } void setDepth (int depth)

{

depth_ = depth;}


10/44

Generic variables should have the same

name as their type void setTopic(Topic* topic)

// NOT: void setTopic(Topic* value)

// NOT: void setTopic(Topic* aTopic)

// NOT: void setTopic(Topic* t)

void connect(Database* database)

// NOT: void connect(Database* db)

// NOT: void connect (Database* oracleDB)


11/44

Variables with a large scope should have long

names, variables with a small scope can have

short names

Scratch variables used for temporary storage orindices are best kept short. A programmer

reading such variables should be able to

assume that its value is not used outside of a

few lines of code. Common scratch variables for

integers are i,j, k, m, n and for characters cand

d.


12/44

The name of the object is implicit, and

should be avoided in a method name

line.getLength();// NOT:line.getLineLength();


13/44

The terms get/setmust be used where an

attribute is accessed directly

employee.getName();employee.setName(name);

matrix.getElement(2, 4);

matrix.setElement(2, 4, value);


14/44

The term compute can be used in

methods where something is computed

valueSet->computeAverage();

matrix->computeInverse()


15/44

The term findcan be used in methods

where something is looked up

vertex.findNearestVertex();matrix.findMinElement();


16/44

Variables representing GUI components

should be suffixed by the component type

name

mainWindow, propertiesDialog,

widthScale, loginText, leftScrollbar,

mainForm, fileMenu, minLabel, exitButton,

yesToggle etc


17/44

Plural form should be used on names

representing a collection of objects

int values[];


18/44

The suffix No should be used for variables

representing an entity number

tableNo, employeeNo


19/44

Iterator variables should be called i,j, ketc

for (int i = 0; i < nTables); i++){ : }


20/44

The prefix is should be used for boolean

variables and methods

isSet, isVisible, isFinished, isFound, isOpen

There are a few alternatives to the is prefix that

fit better in some situations. These are the has,

can and shouldprefixes:

bool hasLicense(); bool canEvaluate();

bool shouldSort();


21/44

Complement names must be used for

complement operations

get/set,add/remove,create/destroy,start/stop,insert/delete,increment/decreme

nt, old/new, begin/end, first/last, up/down,

min/max,next/previous,old/new,open/close

, show/hide, suspend/resume, etc.

Reduce complexity by symmetry


22/44

Abbreviations in names should be avoided

computeAverage();// NOT: compAvg();


23/44

Negated boolean variable names must be

avoided

bool is

Error;// NOT: isNoErrorboolisFound;// NOT: isNotFound


24/44

Exception classes should be suffixed with

Exception

class Access

Exception

{

:

}


25/44

Functions (methods returning something)

should be named after what they return

and procedures (voidmethods) after what

they do

getSum() and add()


26/44

Use of global variables should be

minimized

In C++ there is no reason global variablesneed to be used at all. The same is true

for global functions


27/44

Class variables should never be declared public

The concept of C++ information hiding andencapsulation is violated by public variables. Use privatevariables and access functions instead

One exception to this rule is when the class is essentiallya data structure, with no behavior (equivalent to a Cstruct). In this case it is appropriate to make the class'instance variables public

Note that structs are kept in C++ for compatibility with Conly, and avoiding them increases the readability of thecode by reducing the number of constructs used. Use aclass instead.


28/44

C++ pointers and references should havetheir reference symbol next to the typerather than to the name

float* x;// NOT: float *x;

int& y;// NOT: int &y;

Thepointer-ness orreference-ness of avariable is a property of the type ratherthan the name


29/44

Implicit test for0should not be used other

than for boolean variables and pointers

if (n

Lines != 0)// NOT: if (nLines)

if (value != 0.0)// NOT: if (value)

It is not necessarily defined by the C++

standard that ints and floats 0 areimplemented as binary 0


30/44

Variables should be declared in the

smallest scope possible

Keeping the operations on a variablewithin a small scope, it is easier to control

the effects and side effects of the variable


31/44

Only loop control statements must be

included in the for() construction

sum = 0; for (i = 0; i < 100; i++)sum += value[i];

// NOT: for (i = 0, sum = 0; i < 100; i++)sum += value[i];


32/44

Loop variables should be initialized immediately before the loop

isDone = false;

while (!isDone)

{

:}

// Not

isDone=false;

while(!isDone){

:

}


33/44

do-while loops can be avoided

do-while loops are less readable thanordinary while loops and forloops since

the conditional is at the bottom of the loop.The reader must scan the entire loop inorder to understand the scope of the loop.In addition, do-while loops are not needed.Any do-while loop can easily be rewritteninto a while loop or a forloop.


34/44

The use of break and continue in loops

should be avoided.

These statements should only be used ifthey give higher readability than their

structured counterparts


35/44

The form while(true) should be used for infinite loops

while (true)

{

:

}

for (;;)

{ // NO!

:

}

while (1){ // NO!

:

}


36/44

Functions must always have the return

value explicitly listed

int get

Value()// NOT: getValue() { : }


37/44

Basic indentation should be 2

for (i = 0; i < nElements; i++)

a[i] = 0;

Indentation of 1 is too small to emphasize thelogical layout of the code. Indentation larger than4 makes deeply nested code difficult to read andincreases the chance that the lines must be split.

Choosing between indentation of 2, 3 and 4, 2and 4 are the more common, and 2 chosen toreduce the chance of splitting code lines


38/44

The class declarations should have the

following form:

class SomeClass : public BaseClass {

public: ...

protected: ..private: ...

}


39/44

Method definitions should have the

following form

void some

Method()

{

...

}


40/44

The function return type can be put in the

left column immediately above the function

name

void

MyClass::myMethod(void)

{:

}


41/44

White Space

-Conventional operators should be surrounded

by a space character.

- C++ reserved words should be followed by awhite space.

- Commas should be followed by a white space.

- Colons should be surrounded by white space.

- Semicolons in for statments should be followedby a space character


42/44

Methods should be separated by three

blank lines

By making the space larger than spacewithin a method, the methods will stand

out within the class


43/44

Use//for all comments, including multi-

line comments

// Comment spanning// more than one line


44/44

C++ Practices

Documents