Reactivate the gf-shell command 'pt -transfer'

1 files changed, 21 insertions, 2 deletions

diff --git a/src/compiler/GF/Command/TreeOperations.hs b/src/compiler/GF/Command/TreeOperations.hs
index fc0e6616d..7497eb7e8 100644
--- a/src/compiler/GF/Command/TreeOperations.hs
+++ b/src/compiler/GF/Command/TreeOperations.hs
@@ -5,6 +5,8 @@ module GF.Command.TreeOperations (
   ) where
 
 import PGF(Expr,PGF,CId,compute,mkApp,unApp,unapply,unMeta,exprSize,exprFunctions)
+import PGF.Data(Expr(EApp,EFun))
+import PGF.TypeCheck(inferExpr)
 import Data.List
 
 type TreeOp = [Expr] -> [Expr]
@@ -16,15 +18,17 @@ allTreeOps :: PGF -> [(String,(String,Either TreeOp (CId -> TreeOp)))]
 allTreeOps pgf = [
    ("compute",("compute by using semantic definitions (def)",
       Left  $ map (compute pgf))),
+   ("transfer",("apply this transfer function to all maximal subtrees of suitable type",
+      Right $ \f -> map (transfer pgf f))), -- HL 12/24, modified from gf-3.3
    ("largest",("sort trees from largest to smallest, in number of nodes",
       Left  $ largest)),
-   ("nub",("remove duplicate trees",
+   ("nub\t",("remove duplicate trees",
       Left  $ nub)),
    ("smallest",("sort trees from smallest to largest, in number of nodes",
       Left  $ smallest)),
    ("subtrees",("return all fully applied subtrees (stopping at abstractions), by default sorted from the largest",
       Left  $ concatMap subtrees)),
-   ("funs",("return all fun functions appearing in the tree, with duplications",
+   ("funs\t",("return all fun functions appearing in the tree, with duplications",
       Left  $ \es -> [mkApp f [] | e <- es, f <- exprFunctions e]))
   ]
 
@@ -48,3 +52,18 @@ subtrees :: Expr -> [Expr]
 subtrees t = t : case unApp t of
   Just (f,ts) -> concatMap subtrees ts
   _ -> []  -- don't go under abstractions
+
+-- Apply transfer function f:C -> D to all maximal subtrees s:C of tree e and replace
+-- these s by the values of f(s). This modifies the 'simple-minded transfer' of gf-3.3.
+-- If applied to strict subtrees s of e, better use with f:C -> C only.  HL 12/2024
+
+transfer :: PGF -> CId -> Expr -> Expr
+transfer pgf f e = case inferExpr pgf (appf e) of
+     Left _err -> case e of
+                    EApp g a -> EApp (transfer pgf f g) (transfer pgf f a)
+                    _ -> e
+     Right _ty -> case (compute pgf (appf e)) of
+                    v | v /= (appf e) -> v
+                    _ -> e          -- default case of f, or f has no computation rule
+ where
+  appf = EApp (EFun f)