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.help "switch,case,default" Feb86 language
.ih
NAME
switch -- switch case statement
.ih
SYNTAX
.nf
switch (expr) {
case val1 [, val1,...]:
statements
case val3 [, val3,...]:
statements
(etc.)
default:
statements
}
.fi
.ih
ELEMENTS
.ls expr
An integer-valued expression tested before entry into the switch block.
.le
.ls valN
Integer valued constants used to match expression.
.le
.ls statements
Simple or compound statements to be executed when the appropriate case or
default block is selected.
.le
.ih
DESCRIPTION
The \fIswitch\fR statement provides a multiway branch capability.
The switch expression is evaluated and control branches to the matching
\fIcase\fR block. If there is no match the \fIdefault\fR block, if present,
receives control. If no \fIdefault\fR block is present, the switch is skipped.
Each \fIcase\fR statement consists of a list of values defining the case,
and an executable statement (possibly compound) to be executed if the case
is selected by the switch. Execution will continue until the next case is
reached, at which time a branch out of the \fIswitch\fR statement occurs.
Note this difference from the C switch case, where an explicit \fIbreak\fR
statement is required to exit a switch. If a \fIbreak\fR is used in a CL
switch, it will act upon the loop statement containing the switch, not the
switch itself.
Note that both the switch expression and the case constants may
be integers, or single characters which are evaluated to their
ASCII equivalents.
The \fIdefault\fR statement must be the last statement in the switch block.
.ih
EXAMPLES
1. Multiple cases, no default case.
.nf
switch (opcode) {
case 1:
task1 (args)
case 2:
task2 (args)
case 5:
task5 (args)
}
.fi
2. Multiple values in a case.
.nf
switch (digit) {
case '1','2','3','4','5','6','7':
n = n * 8 + digit - '0'
default:
error (1, "invalid number")
}
.fi
.ih
BUGS
Only integer values are allowed (no strings).
The case values must be constants; ranges are not permitted.
.ih
SEE ALSO
if else, goto
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