Merge pull request #837 from rhendric/for-by

support for <expr> by <expr> loops

Author: vendethiel

lib/ast.js

@@ -155,6 +155,7 @@ exports <<<
             id = []
             @fset 'for' true
             @fset 'to' false
+            @fset 'by' true
         case 'then'
             @fset 'for' false
             @fset 'to' false
@@ -264,7 +265,7 @@ exports <<<
                 then tag = 'RANGE_BY'
                 else if ']' in @closes
                     tag = 'BY'
-                else if @fget 'by'
+                else if @fget 'by' and last.0 is not 'FOR'
                     tag = 'BY'
                     @fset 'by' false
             case 'ever' then if last.0 is 'FOR'

lib/command.js

@@ -634,6 +634,13 @@ eq '0 1 2 3' [f! for til 4].join ' '
 i = 0
 eq '2 4 6' [f! for til 4 when f!].join ' '
 
+x = []
+for <[one two three]> by -1 then x.push ..
+eq 'three two one' x.join ' '
+
+x = [.. for <[one two three]> by -1]
+eq 'three two one' x.join ' '
+
 # index var outside loop
 for v, k in [1]
   void