June 2018 Update

Task/Middle-three-digits/Factor/middle-three-digits.factor

@@ -0,0 +1,26 @@
+USING: combinators formatting io kernel math math.parser
+sequences ;
+IN: rosetta-code.middle-three-digits
+
+CONSTANT: test-values { 123 12345 1234567 987654321 10001 -10001
+    -123 -100 100 -12345 1 2 -1 -10 2002 -2002 0 }
+
+: middle-three ( str -- str' ) [ midpoint@ ] keep
+    [ [ 1 - ] [ 2 + ] bi ] dip subseq ;
+
+: too-short ( -- ) "Number must have at least three digits."
+    print ;
+
+: number-even ( -- ) "Number must have an odd number of digits."
+    print ;
+
+: process ( n -- )
+    abs number>string {
+        { [ dup length 3 < ] [ drop too-short ] }
+        { [ dup length even? ] [ drop number-even ] }
+        [ middle-three print ]
+    } cond ;
+
+: main ( -- ) test-values [ dup "%9d : " printf process ] each ;
+
+MAIN: main