SB05-065: Change list comprehension syntax

From [x | x <- collection, x % 2 == 0]
to   [x for x in collection if x % 2 == 0]

Author: raph-amiard

lkql/extensions/src/lkql-evaluation.adb

@@ -80,7 +80,7 @@ package body LKQL.Evaluation is
    function Eval_Unwrap (Ctx : Eval_Context; Node : L.Unwrap) return Primitive;
 
    function Make_Comprehension_Environment_Iter
-     (Ctx : Eval_Context; Node : L.Arrow_Assoc_List)
+     (Ctx : Eval_Context; Node : L.List_Comp_Assoc_List)
       return Comprehension_Env_Iter;
    --  Given a List of Arrow_Assoc, return an iterator that yields the
    --  environments produced by this list of Arrow_Assoc in the context of a
@@ -607,7 +607,7 @@ package body LKQL.Evaluation is
 
    function Environment_Iter_For_Assoc
      (Ctx    : Eval_Context;
-      Assoc  : L.Arrow_Assoc;
+      Assoc  : L.List_Comp_Assoc;
       Nested : Comprehension_Env_Iter_Access)
       return Comprehension_Env_Iter_Access;
 
@@ -677,16 +677,16 @@ package body LKQL.Evaluation is
    -----------------------------------------
 
    function Make_Comprehension_Environment_Iter
-     (Ctx : Eval_Context; Node : L.Arrow_Assoc_List)
+     (Ctx : Eval_Context; Node : L.List_Comp_Assoc_List)
       return Comprehension_Env_Iter
    is
       Current_Env : Comprehension_Env_Iter_Access := null;
       Res       : Comprehension_Env_Iter;
    begin
       for I in reverse Node.Children'Range loop
          declare
-            Current_Assoc   : constant L.Arrow_Assoc :=
-              Node.Children (I).As_Arrow_Assoc;
+            Current_Assoc   : constant L.List_Comp_Assoc :=
+              Node.Children (I).As_List_Comp_Assoc;
          begin
             Current_Env :=
               Environment_Iter_For_Assoc (Ctx, Current_Assoc, Current_Env);
@@ -705,7 +705,7 @@ package body LKQL.Evaluation is
 
    function Environment_Iter_For_Assoc
      (Ctx    : Eval_Context;
-      Assoc  : L.Arrow_Assoc;
+      Assoc  : L.List_Comp_Assoc;
       Nested : Comprehension_Env_Iter_Access)
       return Comprehension_Env_Iter_Access
    is

lkql/language/lexer.py

@@ -17,6 +17,7 @@ class Token(LexerToken):
     Selector = WithSymbol()
     Match = WithSymbol()
     Rec = WithSymbol()
+    For = WithSymbol()
     Skip = WithSymbol()
     Is = WithSymbol()
     In = WithSymbol()
@@ -108,6 +109,7 @@ class Token(LexerToken):
     (Literal("selector"),                                  Token.Selector),
     (Literal("match"),                                     Token.Match),
     (Literal("rec"),                                       Token.Rec),
+    (Literal("for"),                                       Token.For),
     (Literal("skip"),                                      Token.Skip),
     (Literal("is"),                                        Token.Is),
     (Literal("in"),                                        Token.In),

lkql/language/parser.py

@@ -491,7 +491,7 @@ class Query(Expr):
     pattern = Field(type=BasePattern)
 
 
-class ArrowAssoc(LKQLNode):
+class ListCompAssoc(LKQLNode):
     """
     Arrow association of the form: id <- expr.
     This construction is meant to be used a part of a list comprehension
@@ -508,7 +508,7 @@ class ListComprehension(Expr):
     """
 
     expr = Field(type=Expr)
-    generators = Field(type=ArrowAssoc.list)
+    generators = Field(type=ListCompAssoc.list)
     guard = Field(type=Expr)
 
 
@@ -517,9 +517,11 @@ class BlockExpr(Expr):
     Expression of the form: val id = value; expr
 
     For instance::
+    {
        val x = 40;
        val y = 2;
        x + y
+    }
     """
 
     vals = Field(type=ValDecl.list)
@@ -1028,13 +1030,14 @@ def patterns():
         Opt("(", c(), List(G.named_arg, sep=",", empty_valid=False), ")")
     ),
 
-    arrow_assoc=ArrowAssoc(G.identifier, "<-", G.expr),
-
-    listcomp=ListComprehension("[", G.expr, "|",
-                               List(G.arrow_assoc,
-                                    sep=",", empty_valid=False),
-                               Opt(",", G.expr),
-                               "]"),
+    listcomp=ListComprehension(
+        "[",
+        G.expr, "for",
+        List(ListCompAssoc(G.identifier, "in", G.expr),
+             sep=",", empty_valid=False),
+        Opt("if", G.expr),
+        "]"
+    ),
 
     decl=Or(G.fun_decl,
             G.selector_decl,
@@ -1103,7 +1106,8 @@ def patterns():
     ),
 
     block_expr=BlockExpr(
-        "{", c(), List(G.val_decl, sep=";", empty_valid=False), ";", G.expr, "}"
+        "{", c(), List(G.val_decl, sep=";", empty_valid=False), ";", G.expr,
+        "}"
     ),
 
     val_decl=ValDecl("val", c(), G.identifier, "=", G.expr),

lkql_checker/share/lkql/too_many_dependencies.lkql

@@ -3,6 +3,6 @@ fun result(maxDeps) =
         CompilationUnit(any c @ children is Identifier(any parent(depth=2) is WithClause))
         .body = l @ LibraryItem when {
             val semanticParent = l.item?.semantic_parent();
-            val deps = [x | x <- c, x.referenced_decl() != semanticParent];
+            val deps = [x for x in c if x.referenced_decl() != semanticParent];
             deps.length > maxDeps
         }

testsuite/tests/interpreter/complex_list_comprehension/script.lkql

@@ -1,4 +1,5 @@
-val subtype = select SubtypeIndication
+val subtypes = select SubtypeIndication
 val objects = select ObjectDecl
-print([ o.image & " " & st.image | o <- objects, st <- subtype,
-                                   (o.image & " " & st.image).length != 64])
+print([ o.image & " " & st.image
+       for o in objects, st in subtypes
+       if (o.image & " " & st.image).length != 64])

testsuite/tests/interpreter/simple_list_comprehension/script.lkql

@@ -1,3 +1,3 @@
 val all = select p @ _
-val decls = [a | a <- all, a is ObjectDecl]
+val decls = [a for a in all if a is ObjectDecl]
 print(decls)

testsuite/tests/parser/list_comprehension/input

@@ -1 +1 @@
-[x + y| x <- valuesList, y <- valuesList2, x.property == "Foo"]
+[x + y for x in valuesList, y in valuesList2 if x.property == "Foo"]

testsuite/tests/parser/list_comprehension/test.out

@@ -8,13 +8,13 @@ ListComprehension
 |  |right:
 |  |  Identifier: y
 |generators:
-|  ArrowAssocList
-|  |  ArrowAssoc
+|  ListCompAssocList
+|  |  ListCompAssoc
 |  |  |binding_name:
 |  |  |  Identifier: x
 |  |  |coll_expr:
 |  |  |  Identifier: valuesList
-|  |  ArrowAssoc
+|  |  ListCompAssoc
 |  |  |binding_name:
 |  |  |  Identifier: y
 |  |  |coll_expr: