Dokumentation zu: switch(LPC)

HR Image


        switch (expr) block

        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.

        Typical usage:

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

        In C, the grammar for switch() is

            switch (expr) statement

        allowing constructs like

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

        In LPC a switch has to be followed by a block that contains the
        case labels directly. In contrast to C the group of statements
        following a case label have their own lexical scope so that
        variable declarations may not cross case labels.

        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.
        LDMud 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 3.3.718 disallowed case labels in inner blocks and variable
          declarations that cross case labels.

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

Start » Magierhandbuch » Docu » LPC » Switch Letzte Generierung: 25.04.2021, 01:58
Email an:
Valid HTML 4.01!