refactor four example solutions

config.json

@@ -1020,7 +1020,8 @@
         ],
         "prerequisites": [
           "conditionals",
-          "booleans"
+          "booleans",
+          "combinators"
         ],
         "difficulty": 3
       },

exercises/practice/armstrong-numbers/.meta/example.factor

@@ -1,24 +1,7 @@
-USING: assocs kernel locals math math.functions math.order sequences vectors ;
+USING: kernel locals math math.functions math.parser sequences ;
 IN: armstrong-numbers
 
-:: digits ( x -- digits )
-    x 10 /mod :> x! :> xs!
-    V{ } clone :> digits
-    x digits push
-
-    [ xs 0 = not ]
-    [
-        xs 10 /mod x! xs!
-        x digits push
-    ] while
-
-    digits reverse ;
-
-:: powsum ( x -- powsum )
-    x digits :> digs
-    digs length :> len
-
-    digs [ len ^ ] map sum ;
-
-: armstrong? ( n -- ? )
-    [ ] [ powsum ] bi = ;
+:: armstrong? ( n -- ? )
+    n number>string [ CHAR: 0 - ] map :> digits
+    digits length :> len
+    digits [ len ^ ] map-sum n = ;

exercises/practice/gigasecond/.meta/example.factor

@@ -1,28 +1,11 @@
-USING: accessors calendar kernel math math.parser sequences
-splitting ;
+USING: calendar combinators formatting kernel math.parser sequences splitting ;
 IN: gigasecond
 
-<PRIVATE
-
-: pad2 ( n -- str ) number>string 2 CHAR: 0 pad-head ;
-
-! Parse "YYYY-MM-DD" or "YYYY-MM-DDTHH:MM:SS" into a timestamp.
-:: parse-moment ( str -- timestamp )
-    str "T" split1 :> ( datepart timepart )
-    datepart "-" split [ string>number ] map first3 :> ( y mo d )
-    timepart [ "00:00:00" ] unless* ":" split [ string>number ] map
-    first3 :> ( h mi s )
-    y mo d h mi s instant <timestamp> ;
-
-:: format-moment ( ts -- str )
-    ts year>> number>string
-    ts month>> pad2 "-" glue
-    ts day>> pad2 "-" glue
-    ts hour>> pad2 "T" glue
-    ts minute>> pad2 ":" glue
-    ts second>> >integer pad2 ":" glue ;
-
-PRIVATE>
-
 : gigasecond-after ( moment -- moment )
-    parse-moment 1000000000 seconds time+ format-moment ;
+    "T" split1
+    [ "-" split [ string>number ] map first3 ]
+    [ "00:00:00" or ":" split [ string>number ] map first3 ]
+    bi*
+    instant <timestamp> 1000000000 seconds time+
+    [ >date< ] [ >time< ] bi
+    "%04d-%02d-%02dT%02d:%02d:%02d" sprintf ;

exercises/practice/leap/.meta/example.factor

@@ -1,10 +1,5 @@
-USING: combinators kernel math ;
+USING: combinators kernel math.functions ;
 IN: leap
 
 : leap-year? ( year -- ? )
-    {
-        { [ dup 400 mod zero? ] [ drop t ] }
-        { [ dup 100 mod zero? ] [ drop f ] }
-        { [ dup   4 mod zero? ] [ drop t ] }
-        [ drop f ]
-    } cond ;
+    [ 4 divisor? ] [ 100 divisor? not ] [ 400 divisor? ] tri or and ;

exercises/practice/word-count/.meta/example.factor

@@ -1,24 +1,10 @@
-USING: assocs hashtables kernel locals math sequences splitting
-strings unicode ;
+USING: assocs fry kernel sequences splitting unicode ;
 IN: word-count
 
-: word-char? ( ch -- ? )
-    dup Letter? over digit? or swap CHAR: ' = or ;
-
-:: strip-apostrophes ( str -- str' )
-    str dup empty? not [
-        dup first CHAR: ' = [ rest ] when
-        dup empty? not [ dup last CHAR: ' = [ but-last ] when ] when
-    ] when ;
-
-:: count-words ( sentence -- counts )
-    H{ } clone :> result
-    sentence >lower
-    [ word-char? not ] split-when
-    [ empty? not ] filter
-    [ strip-apostrophes ] map
-    [ empty? not ] filter
-    [| word |
-        word result at 0 or 1 + word result set-at
-    ] each
-    result ;
+: count-words ( sentence -- counts )
+    >lower
+    [ [ CHAR: ' = ] [ digit? ] [ Letter? ] tri or or not ] split-when
+    [ [ CHAR: ' = ] trim ] map
+    harvest
+    H{ } clone
+    [ '[ _ inc-at ] each ] keep ;