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https://github.com/ldmud/ldmud
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77225dc84c
Switch now explicitly expects case/default statements in the switch
block and puts the non-case statements afterwards into their own
block scope. (Bug #584)
git-svn-id: svn://svn.bearnip.com/ldmud/trunk@2454 56160b6e-f8f8-0310-bd54-bccebfe6a2f2
93 lines
3.1 KiB
Text
93 lines
3.1 KiB
Text
NAME
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switch
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SYNTAX
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switch (expr) block
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DESCRIPTION
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Branch to the case label in statement that matches expr.
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If no matching case label is found (by value or by type),
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branch to the default label in statement.
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A case label has the form
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case expr_n :
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where expr_n must be constant, or the form
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case expr_n1 .. expr_n2 :
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where expr_n1 and expr_n2 must be numeric constants and
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expr_n1 < expr_n2.
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Either all case labels have to be strings or all have to be
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numeric. Only 0 is special: it is allowed in a switch
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statement where all other labels are strings.
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A default label has the form
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default :
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The default label defaults to the end of statement if not
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given explicitly.
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Whenever a 'break' statement is executed inside 'statement' a
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branch to the end of the switch statement is performed.
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EXAMPLE
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Typical usage:
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switch(random(100)) {
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case 0 .. 22 : write("Nothing happens"); break;
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case 23 .. 27 :
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write("You are surrounded by a golden glow");
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this_player()->heal_self(random(3));
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break;
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case 28 .. 32 :
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write("The water was poisoned!\n");
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this_player()->add_exp(this_player()->hit_player(random(4)));
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break;
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case 33 : write("You hear a voice whispering: "+random_hint());
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/* fall through */
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case 34 :
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write("While you didn't pay attention, a water demon "
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"snatches a coin out of your purse!\n");
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this_player()->add_money(-1);
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break;
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default : write "You hear some strange noises\n"; break;
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case 42 : return;
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case 99 : write("It tastes good.\n";
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}
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NOTE
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In C, the grammar for switch() is
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switch (expr) statement
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allowing constructs like
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switch (expr)
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while (expr2)
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{
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case 1: ...
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case 2: ...
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}
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In LPC a switch has to be followed by a block that contains the
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case labels directly. In contrast to C the group of statements
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following a case label have their own lexical scope so that
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variable declarations may not cross case labels.
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HISTORY
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LDMud 3.2.10 constrained the grammar to require a block for the
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switch() body, not just a statement. This differs from the C
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syntax, but was necessary as the compiler didn't handle
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the statement case correctly.
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LDMud 3.3 allowed to pass values of the wrong type to switch(), the
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driver would in that case use the default case. Before, values of
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the wrong type caused a runtime error.
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LDMud 3.3.718 disallowed case labels in inner blocks and variable
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declarations that cross case labels.
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SEE ALSO
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for(LPC), foreach(LPC), do-while(LPC), if(LPC), while(LPC)
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