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parseen.r

Rebol[ Title: "Parseen" Date: 28-Nov-2010/9:09:13+1:00 History: [ 26/Apr/2003/11:30 "working version" 21/Dec/2004/13:40 "thru-rule added" 22/Dec/2004/8:05 "lit added" 18-Mar-2007/1:45:14+1:00 "do-block corrected" 18-Mar-2007/9:57:05+1:00 "dialect upgraded" 16-Oct-2010/23:13:26+2:00 "then-rule added" "the parseen function removed" "lit rule renamed to quote-rule" 31-Oct-2010/9:16:55+1:00 "if-rule added" ] File: %parseen.r Author: "Ladislav Mecir" Purpose: {Parse enhancements for R2} ] comment [ ; Example # 1 rule: not-rule [any "a" "b"] parse "ab" rule parse "b" rule parse "" rule ; Example # 2 rule: not-rule "aa" parse "ab" [rule any "a" "b"] parse "aab" [rule any "a" "b"] ; Example # 3 rule: not-rule quote-rule 1 parse [1] [any [rule skip]] parse [2] [any [rule skip]] ; Example # 4 rule: not-rule integer! parse [1 a] [rule to end] parse [a 1] [rule to end] ; Example # 5 parse [a b c 1 d] [any [rule skip]] parse [a b c d e] [any [rule skip]] ; Example # 6 result: "" rule: to-rule [" " | "<br>"] parse/all "aa" [rule result: to end] probe result parse/all "a a<br>" [rule result: to end] probe result parse/all "ab<br> " [rule result: to end] probe result ; Example # 7 digit: charset [#"0" - #"9"] four-digit: [4 digit] rule: to-rule four-digit parse/all "abcd 1234" [rule copy fd four-digit to end] probe fd ; Example # 8 pm: charset "+-" rule: thru-rule pm parse "assdasasasa+" [copy t rule] probe t ; Example # 9 rule: quote-rule first ['ahoj] parse ['ahoj] rule parse [ahoj] rule ; Example # 10 rule: if-rule (false) parse [] rule ; Example # 11 rule: if-rule (true) parse [] rule ] ; a rule that always fails, opposite to none fail: [end skip] use [x y z] [ then-rule: func [ {generate the A THEN B | C rule} a b c /local d ] [ d: copy first [(x:)] reduce [reduce [a append/only d b '| append/only d c] 'x] ] not-rule: func [ {generate the NOT A rule} a ] [ reduce [append reduce [a] [(x: fail) | (x: none)] 'x] ] and-rule: func [ {generate the AND A rule} a ] [ reduce [append reduce [a] [(x: fail) | (x: none)] fail '| 'x] ] to-rule: func [ {generate the TO A rule} a ] [ reduce [ 'any reduce [ append reduce [a] [(x: fail y: none) | (x: 'skip y: fail)] 'x ] 'y ] ] thru-rule: func [ {generate the THRU A rule} a ] [ reduce [ 'any reduce [ append reduce [a] [x: (y: fail z: [:x]) | (y: 'skip z: fail)] 'y ] 'z ] ] quote-rule: func [ {generate the QUOTE A rule} a /local b ] [ b: copy/deep [copy x skip (y: unless equal? x) y] append/only append/only fourth b reduce [:a] [fail] b ] if-rule: func [ {generate the IF A rule} 'a [paren!] ] [ a: reduce [first [x:] 'either :a [none] [[end skip]]] reduce [to paren! a 'x] ] ]
halt ;; to terminate script if DO'ne from webpage