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Task/Substring/Factor/substring.factor

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+USING: math sequences kernel ;
+
+! starting from n characters in and of m length
+: subseq* ( from length seq -- newseq ) [ over + ] dip subseq ;
+
+! starting from n characters in, up to the end of the string
+: dummy ( seq n -- tailseq ) tail ;
+
+! whole string minus last character
+: dummy1 ( seq -- headseq ) but-last ;
+
+USING: fry sequences kernel ;
+! helper word
+: subseq-from-* ( subseq len seq quot -- seq ) [ nip ] prepose 2keep subseq* ; inline
+
+! starting from a known character within the string and of m length;
+: subseq-from-char ( char len seq -- seq ) [ index ] subseq-from-* ;
+
+! starting from a known substring within the string and of m length.
+: subseq-from-seq ( subseq len seq -- seq ) [ start ] subseq-from-* ;