operator sections

TODO.md

@@ -1,7 +1,7 @@
 
 ## TODO
 
-- [ ] change "in prefix position" and "trailing operator" errors to do sections
+- [x] change "in prefix position" and "trailing operator" errors to do sections
 - [ ] maybe add fat arrows, I keep wanting to type them, `{{...}}` is a little ugly
   - There may be ambiguity issues at the parsing level, but we don't have typecase, so...
 - [x] get some names on add missing cases (if not too difficult)
@@ -211,7 +211,7 @@
   - Makes inference easier, cleaner output, and allows `foo $ \ x => ...`
   - [ ] `$` no longer works inside ≡⟨ ⟩ - sort out how to support both that and `$ \ x => ...` (or don't bother)
     - We'd either need to blacklist all non-initial mixfix bits at the appropriate spots or always pass around a terminating token.
-    - I'm leaning towards _no_ here, because I may want to lift mixfix processing out of the parsing step in the future. This isn't
+    - I'm leaning towards _no_ here, because I may want to lift mixfix processing out of the parsing step in the future.
 - [x] **Translate newt to newt**
   - [x] Support @ on the LHS
   - [x] if / then / else sugar

scripts/test

@@ -30,7 +30,7 @@ for fn in tests/*.newt ; do
   fi
   # if there is a golden file, run the code and compare output
   if [ -f ${fn}.golden ]; then
-    bun run out.js > tmp/${bn}.out
+    node out.js > tmp/${bn}.out
     if [ $? != "0" ]; then
       echo Run failed for $fn
       failed=$((failed + 1))

src/Lib/Parser.newt

@@ -219,7 +219,11 @@ pratt ops prec stop left spine = do
                 ((_, fc, right) :: rest) => do
                   (right, rest) <- pratt ops pr stop right rest
                   pratt ops prec stop (RApp (getFC left + getFC right) left right Explicit) rest
-                _ => fail "trailing operator"
+                _ =>
+                  -- Trailing operator section, like (2 +)
+                  pratt ops prec stop left Nil
+                  -- fail "trailing operator"
+
 
     runRule p fix stop (nm :: rule) left spine = do
       case spine of
@@ -240,8 +244,10 @@ pratt ops prec stop left spine = do
            -- TODO False should be an error here
          Just (MkOp name p fix True rule) => do
             runRule p fix stop rule (RVar fc name) spine
-         Just (MkOp name p fix False rule) => do
+         Just (MkOp name p fix False rule) =>
-            fail "got infix \{show name} in prefix position"
+            -- REVIEW We could also use a lambda with a fresh name
+            runRule p fix stop rule (RApp fc (RVar fc "flip") (RVar fc name) Explicit) spine
+            -- fail "got infix \{show name} in prefix position"
          _ =>
           pure (left, spine)
     runPrefix stop left spine = pure (left, spine)

tests/ErrMsg.newt

@@ -1,14 +0,0 @@
-module ErrMsg
-
-import Prelude
-
-infixl 5 _$$_
-
-_$$_ : Nat → (Nat → Nat) → Nat
-a $$ b = a + b a
-
--- Say something other than expected record
--- Why do we get there? shouldn't the progress made by parseDef short circuit the <|>?
-blah : Nat → Nat
-blah x = x $$ $ \ y => y
-

tests/ErrMsg.newt.fail

@@ -1,6 +0,0 @@
-*** Process tests/ErrMsg.newt
-module Prelude
-module ErrMsg
-ERROR at tests/ErrMsg.newt:13:15--13:16: trailing operator
-
-Compile failed

tests/Section.newt

@@ -0,0 +1,20 @@
+module Section
+
+import Prelude
+
+-- got infix in prefix position
+add : Int → Int → Int
+add = (+)
+
+add2 : Int → Int
+add2 = (+ 2)
+
+-- trailing operator
+add2' : Int → Int
+add2' = (2 +)
+
+main : IO Unit
+main = do
+    printLn $ (+) 2 3
+    printLn $ (+ 3) 2
+    printLn $ (2 +) 3

tests/Section.newt.golden

@@ -0,0 +1,3 @@
+5
+5
+5

tests/TrailDollar.newt

@@ -0,0 +1,13 @@
+module TrailDollar
+
+import Prelude
+
+infixl 5 _$$_
+
+_$$_ : Nat → (Nat → Nat) → Nat
+a $$ b = a + b a
+
+-- Previously this didn't parse, but it does with operator section support.
+blah : Nat → Nat
+blah x = x $$ $ \ y => y
+