REBOL [ File: %substr.r Date: 16-Dec-2003 Title: "Simple substring function - with the addition of error message to prevent 'none' shown" Purpose: "Working around string series" Author: "Yosef H. da Iry" library: [ level: 'beginner platform: 'all type: [tutorial tool] domain: [text text-processing] tested-under: none support: none license: none see-also: none ] ] substr: func ["Substring function" str [string! word!] "string" start-index "started index" /slen "refinement" len "number of characters to be taken"] [ size: length? str either slen [ either start-index + len > size [ print "ERROR !! Substring operation over-limit the string size !!" ] [ ;create a new string block for the new string ;the length is equal to len new-str: make string! len ;calculating the end-index end-index: start-index + len - 1 ;copying the content for i start-index end-index 1 [ char: pick str i append new-str char ] ;print new string print new-str ] ] [ either start-index > size [ print "ERROR !! Substring operation over-limit the string size !!" ] [ ;traversing the block up to the desired start-index loop start-index [ str: next str ] ;move one back due to the loop above str: back str ;copy the new string new-str: copy str ;print new string print new-str ] ] ]