A-M baby

Task/Align-columns/Factor/align-columns.factor

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+USING: fry io kernel math math.functions math.order sequences
+splitting strings ;
+IN: rosetta.column-aligner
+
+CONSTANT: example-text "Given$a$text$file$of$many$lines,$where$fields$within$a$line$
+are$delineated$by$a$single$'dollar'$character,$write$a$program
+that$aligns$each$column$of$fields$by$ensuring$that$words$in$each$
+column$are$separated$by$at$least$one$space.
+Further,$allow$for$each$word$in$a$column$to$be$either$left$
+justified,$right$justified,$or$center$justified$within$its$column."
+
+: split-and-pad ( text -- lines )
+    "\n" split [ "$" split harvest ] map
+    dup [ length ] [ max ] map-reduce
+    '[ _ "" pad-tail ] map ;
+
+: column-widths ( columns -- widths )
+    [ [ length ] [ max ] map-reduce ] map ;
+
+SINGLETONS: +left+ +middle+ +right+ ;
+
+GENERIC: align-string ( str n alignment -- str' )
+
+M: +left+ align-string  drop CHAR: space pad-tail ;
+M: +right+ align-string drop CHAR: space pad-head ;
+
+M: +middle+ align-string
+    drop
+    over length - 2 /
+    [ floor CHAR: space <string> ]
+    [ ceiling CHAR: space <string> ] bi surround ;
+
+: align-columns ( columns alignment -- columns' )
+    [ dup column-widths ] dip '[
+        [ _ align-string ] curry map
+    ] 2map ;
+
+: print-aligned ( text alignment -- )
+    [ split-and-pad flip ] dip align-columns flip
+    [ [ write " " write ] each nl ] each ;