Dokumentation zu: switch(LPC)

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NAME
        switch

SYNTAX
        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
        for(LPC), foreach(LPC), do-while(LPC), if(LPC), while(LPC)


Start » Magierhandbuch » Docu » LPC » Switch Letzte Generierung: 16.04.2009, 21:44
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