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REBOL [ Title: "CASE multiple conditional function" Date: 27-Nov-2005 File: %case.r Purpose: { Provide a generalized multiple conditional function for situations that would otherwise call for deeply nested EITHER blocks. CASE is more general than SWITCH because the conditions can be any DO-able block rather than being based on a single value. This can be used simply to allow a SWITCH-like behavior that supports ranges instead of single values, e.g.: print case [ [ lesser? x 1 ] [ "x < 1" ] [ equal? x 1 ] [ "x = 1" ] [ greater? x 1 ] [ "x > 1"] ] It can also be used for more complex situations, since any DO-able block can be used for the condition block. } Author: "Christopher M. Dicely" Version: 1.0.0 eMail: %cmdicely--gmail--com library: [ level: 'beginner platform: 'all type: 'function domain: 'extension tested-under: [ view on [WinXP] ] support: none license: none see-also: none ] ] case: func [ "Multiple conditional function" cases [block!] { Block containing alternating series of: COND-BLOCK which is evaluated and DO-BLOCK which is evaluated if COND-BLOCK is true. Does first DO-BLOCK where the COND-BLOCK is true and returns the value returned by that DO-BLOCK } /default "Execute default-block if no conditions are true" default-block [block!] "Block to execute if no conditions are true" /local retval result errval is-done ] [ retval: none is-done: false forskip cases 2 [ if do first cases [ if error? result: try [ retval: do second cases ] [ { Handles the case where the DO-BLOCK doesn't return a value; sets retval to none } errval: disarm result either equal? result2/code 301 [ retval: none ] [ throw result ] ] is-done: true break ] ] if all [ default not is-done ] [ retval: do default-block ] return retval ]
halt ;; to terminate script if DO'ne from webpage