| MG Mud User | 88f1247 | 2016-06-24 23:31:02 +0200 | [diff] [blame^] | 1 | NAME |
| 2 | switch |
| 3 | |
| 4 | SYNTAX |
| 5 | switch (expr) block |
| 6 | |
| 7 | DESCRIPTION |
| 8 | Branch to the case label in statement that matches expr. |
| 9 | If no matching case label is found (by value or by type), |
| 10 | branch to the default label in statement. |
| 11 | |
| 12 | A case label has the form |
| 13 | |
| 14 | case expr_n : |
| 15 | |
| 16 | where expr_n must be constant, or the form |
| 17 | |
| 18 | case expr_n1 .. expr_n2 : |
| 19 | |
| 20 | where expr_n1 and expr_n2 must be numeric constants and |
| 21 | expr_n1 < expr_n2. |
| 22 | |
| 23 | Either all case labels have to be strings or all have to be |
| 24 | numeric. Only 0 is special: it is allowed in a switch |
| 25 | statement where all other labels are strings. |
| 26 | |
| 27 | A default label has the form |
| 28 | |
| 29 | default : |
| 30 | |
| 31 | The default label defaults to the end of statement if not |
| 32 | given explicitly. |
| 33 | |
| 34 | Whenever a 'break' statement is executed inside 'statement' a |
| 35 | branch to the end of the switch statement is performed. |
| 36 | |
| 37 | EXAMPLE |
| 38 | Typical usage: |
| 39 | |
| 40 | switch(random(100)) { |
| 41 | case 0 .. 22 : write("Nothing happens"); break; |
| 42 | case 23 .. 27 : |
| 43 | write("You are surrounded by a golden glow"); |
| 44 | this_player()->heal_self(random(3)); |
| 45 | break; |
| 46 | case 28 .. 32 : |
| 47 | write("The water was poisoned!\n"); |
| 48 | this_player()->add_exp(this_player()->hit_player(random(4))); |
| 49 | break; |
| 50 | case 33 : write("You hear a voice whispering: "+random_hint()); |
| 51 | /* fall through */ |
| 52 | case 34 : |
| 53 | write("While you didn't pay attention, a water demon " |
| 54 | "snatches a coin out of your purse!\n"); |
| 55 | this_player()->add_money(-1); |
| 56 | break; |
| 57 | default : write "You hear some strange noises\n"; break; |
| 58 | case 42 : return; |
| 59 | case 99 : write("It tastes good.\n"; |
| 60 | } |
| 61 | |
| 62 | NOTE |
| 63 | In C, the grammar for switch() is |
| 64 | |
| 65 | switch (expr) statement |
| 66 | |
| 67 | allowing constructs like |
| 68 | |
| 69 | switch (expr) |
| 70 | while (expr2) |
| 71 | { |
| 72 | case 1: ... |
| 73 | case 2: ... |
| 74 | } |
| 75 | |
| 76 | In LPC a switch has to be followed by a block that contains the |
| 77 | case labels directly. In contrast to C the group of statements |
| 78 | following a case label have their own lexical scope so that |
| 79 | variable declarations may not cross case labels. |
| 80 | |
| 81 | HISTORY |
| 82 | LDMud 3.2.10 constrained the grammar to require a block for the |
| 83 | switch() body, not just a statement. This differs from the C |
| 84 | syntax, but was necessary as the compiler didn't handle |
| 85 | the statement case correctly. |
| 86 | LDMud 3.3 allowed to pass values of the wrong type to switch(), the |
| 87 | driver would in that case use the default case. Before, values of |
| 88 | the wrong type caused a runtime error. |
| 89 | LDMud 3.3.718 disallowed case labels in inner blocks and variable |
| 90 | declarations that cross case labels. |
| 91 | |
| 92 | SEE ALSO |
| 93 | for(LPC), foreach(LPC), do-while(LPC), if(LPC), while(LPC) |