If statement
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If statements allow different actions to be taken depending on a condition. An if statement consists of a condition, a then clause, and an else clause. If the condition is true then the then clause is executed, otherwise the else clause is executed. If no else clause is supplied, then nothing is executed if the condition is false. The condition consists of an expression which will be evaluated at runtime and compared with the value true. The then and else clauses consist of zero or more statements.
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[edit] Typical Use
Typical syntax is
if criterion1
action1
else
if criterion2
action2
else
action3
When the purpose of the if statement is to return one of two values, depending on a condition, the Ternary Operator may be used in some languages (e.g. C, awk) as follows:
condition ? expression1 : expression2;
The ternary operator returns the value of whichever action it takes, making it a useful function. In this way, it differs from the if statement, which does not (in most languages) return a value. The ternary operator example above is similar but (not quite identical) to:
if condition return(expression1) else return(expression2)
When several if statements are used in a cascade to choose between several options, a Switch Statement might be worth considering as a more readable and maintainable replacement.
[edit] Code Snippets
[edit] C
[edit] Ruby
[edit] Visual Basic
If booleanExpression then statement1; Else statement2; End If
[edit] C#
if( booleanExpression ) statement1; else statement2;
