If statement
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If statements allow different actions to be taken depending on a Boolean expression, or "condition." An if statement consists of a condition and two statements (or "clauses"), commonly known as the then (or if) and else clauses, in that order. The then statement is only executed if the condition is true; otherwise, the else statement is executed if it exists.
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[edit] Pseudocode
Typical syntax is
if criterion1
action1
else
if criterion2
action2
else
action3
When the purpose of the if statement is to return/assign one of two values depending on the condition, the ternary operator may be useful.
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] Examples
[edit] Curly bracket programming languages
if (expr) {
// statement 1
} else {
// statement 2
}
expr must be a condition (see above).
if (false) {
// This will never happen!
}
for if statements where there is only one option the brackets can be left out.
if(expr) do_this(); else do_that();
where the statement controls how the function exits you can leave out the else too.
if(expr) return do_this(); return do_that();
[edit] Ruby
var = false
if var {
print "foobar is y\n"
}
else {
print "foobar is n\n"
}
[edit] Visual Basic
If booleanExpression Then statement1 Else statement2 End If
[edit] Python
if expr:
# statement 1
else:
# statement 2
or
if var==1:
#Something
elif var>4:
#Something
else:
#Something
[edit] See Also
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