Laine at 16:59, 11 June 2007

Laine — Mon, 11 Jun 2007 16:59:01 GMT

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==Synopsis==

switch (expr) block;

==Description==
Branch to the case label in statement that matches expr.
If no matching case label is found (by value or by type),
branch to the default label in statement.

A case label has the form

case expr_n :

where expr_n must be constant, or the form

case expr_n1 .. expr_n2 :

where expr_n1 and expr_n2 must be numeric constants and
expr_n1 < expr_n2.

Either all case labels have to be strings or all have to be
numeric. Only 0 is special: it is allowed in a switch
statement where all other labels are strings.

A default label has the form

default :

The default label defaults to the end of statement if not
given explicitly.

Whenever a 'break' statement is executed inside 'statement' a
branch to the end of the switch statement is performed.

==Example==

Typical usage:

switch(random(100)) {
case 0 .. 22 : write("Nothing happens"); break;
case 23 .. 27 :
write("You are surrounded by a golden glow");
this_player()->heal_self(random(3));
break;
case 28 .. 32 :
write("The water was poisoned!\n");
this_player()->add_exp(this_player()->hit_player(random(4)));
break;
case 33 : write("You hear a voice whispering: "+random_hint());
/* fall through */
case 34 :
write("While you didn't paid attention, a water demon snatches\n"
"a coin out of your purse!\n");
this_player()->add_money(-1);
break;
default : write "You hear some strange noises\n"; break;
case 42 : return;
case 99 : write("It tastes good.\n";
}

==Bugs==

In C, the grammar for switch() is

switch (expr) block

allowing constructs like

switch (expr)
while (expr2)
{
case 1: ...
case 2: ...
}

The LPC compiler currently can't handle neither statements as switch
body, nor case labels embedded in inner loops.

==History==

LDMud 3.2.9/3.3 allowed to pass values of the wrong type to switch(),
the driver would in that case use the default case. Before, values
of the wrong type caused a runtime error.

LDMud 3.2.10 constrained the grammar to require a block for the
switch() body, not just a statement. This differs from the C
syntax, but was necessary as the compiler didn't handle
the statement case correctly.

==See Also==
[[man for|for(LPC)]], [[man foreach|foreach(LPC)]], [[man do while|do-while(LPC)]], [[man if|if(LPC)]], [[man while|while(LPC)]]

Man switch - Revision history

Laine at 16:59, 11 June 2007