Changeset 17865 for src/Pugs/Prim/List.hs

Timestamp:

09/16/07 01:53:07 (14 months ago)

Author:

ryporter

Message:

adding support for first() to pugs

Files:

• src/Pugs/Prim/List.hs (modified) (2 diffs)

src/Pugs/Prim/List.hs

@@ -5 +5 @@
     op1Min, op1Max, op1Uniq,
     op2Pick,
-    op2ReduceL, op2Reduce, op2Grep, op2Map, op2Join,
+    op2ReduceL, op2Reduce, op2Grep, op2First, op2Map, op2Join,
     sortByM,
     op1HyperPrefix, op1HyperPostfix, op2Hyper,
@@ -331 +331 @@
     return $ VList vals
 
+op2First :: Val -> Val -> Eval Val
+op2First sub@(VCode _) list = op2First list sub
+op2First list sub = do
+  (VList vals) <- (op2Grep list sub)
+  if (length vals) > 0 
+    then return $ (vals !! 0)
+    else fail $ "Cannot call first() with a filter that removes all elements from the input list"
+
 op2Map :: Val -> Val -> Eval Val
 op2Map sub@(VCode _) list = op2Map list sub