TO ENCODE :STRING
;encodes all digraphs in :string as single characters 
;in line with the pairings provided by :digraphs
IF EMPTY? :STRING [OP "] 
IF EMPTY? BF :STRING [OP :STRING] 
MAKE "TRANSLATION FIND WORD FIRST :STRING FIRST BF :STRING :DIGRAPHS 
IF EMPTY? :TRANSLATION [OP WORD FIRST :STRING ENCODE BF :STRING] 
OP WORD LAST :TRANSLATION ENCODE BF BF :STRING 
END

TO FIND :KEY :DATA.LIST
;retrieves any sub-list of :data.list which contains :key
IF EMPTY? :DATA.LIST [OP []] 
IF MEMBER? :KEY FIRST :DATA.LIST [OP FIRST :DATA.LIST] 
OP FIND :KEY BF :DATA.LIST 
END

TO DECODE :STRING
;decodes all digraph codes in :string as two character sequences 
;in line with the pairings provided by :digraphs
IF EMPTY? :STRING [OP "] 
MAKE "TRANSLATION FIND FIRST :STRING :DIGRAPHS 
IF EMPTY? :TRANSLATION [OP WORD FIRST :STRING ENCODE BF :STRING] 
OP WORD FIRST :TRANSLATION DECODE BF :STRING 
END

MAKE "DIGRAPHS [[CH £] [TH ^] [DH {] [SH $] [ZH %] [NG }]]
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