move less function to common + add list:unzip

mods/common.elv

@@ -25,3 +25,7 @@ fn cexec {|cond v1 v2|
     put $r
   }
 }
+
+fn less {|cmp|
+  put {|e1 e2| < ($cmp $e1 $e2 0)
+}

mods/list.elv

@@ -126,6 +126,19 @@ fn first {|&from=$nil &reverse=$false cb @argv|
   }
 }
 
+fn unzip {|cb @argv|
+  var a1 a2 = [] []
+  loop $@argv | each {|e|
+    var i v = $@e
+    if ($cb $i $v) {
+      set @a1 = $@a1 $v
+    } else {
+      set @a2 = $@a2 $v
+    }
+  }
+  put $a1 $a2
+}
+
 fn reduce {|acc cb @argv|
   each {|e|
     set acc = ($cb $acc $e)
@@ -169,10 +182,6 @@ fn swap {|i j @argv|
   }
 }
 
-fn less {|cb|
-  put {|a b| < ($cb $a $b) 0 }
-}
-
 fn sort {|cb @argv|
-  order &less-than=(less $cb) (-l $@argv)
+  order &less-than=(common:less $cb) (-l $@argv)
 }