From 37d7abd69402f0e7a78d4d2f2d78996409a8563a Mon Sep 17 00:00:00 2001
From: Eelco Dolstra <e.dolstra@tudelft.nl>
Date: Mon, 25 Oct 2004 16:54:56 +0000
Subject: * New language feature: with expressions.

  The expression `with E1; E2' evaluates to E2 with all bindings in
  the attribute set E1 substituted.  E.g.,

    with {x = 123;}; x

  evaluates to 123.  That is, the attribute set E1 is in scope in E2.

  This is particularly useful when importing files containing lots
  definitions.  E.g., instead of

    let {
      inherit (import ./foo.nix) a b c d e f;

      body = ... a ... f ...;
    }

  we can now say

    with import ./foo.nix;

    ... a ... f ...

  I.e., we don't have to say what variables should be brought into scope.
---
 src/libexpr/parser.y | 12 +++++-------
 1 file changed, 5 insertions(+), 7 deletions(-)

(limited to 'src/libexpr/parser.y')

diff --git a/src/libexpr/parser.y b/src/libexpr/parser.y
index 347516f69239..88ee8326b8d3 100644
--- a/src/libexpr/parser.y
+++ b/src/libexpr/parser.y
@@ -41,11 +41,11 @@ ATerm makePos(YYLTYPE * loc, void * data)
   ATermList ts;
 }
 
-%type <t> start expr expr_function expr_assert expr_if expr_op
+%type <t> start expr expr_function expr_if expr_op
 %type <t> expr_app expr_select expr_simple bind inheritsrc formal
 %type <ts> binds ids expr_list formals
 %token <t> ID INT STR PATH URI
-%token IF THEN ELSE ASSERT LET REC INHERIT EQ NEQ AND OR IMPL
+%token IF THEN ELSE ASSERT WITH LET REC INHERIT EQ NEQ AND OR IMPL
 
 %nonassoc IMPL
 %left OR
@@ -67,12 +67,10 @@ expr_function
     { $$ = ATmake("Function(<term>, <term>, <term>)", $2, $5, CUR_POS); }
   | ID ':' expr_function
     { $$ = ATmake("Function1(<term>, <term>, <term>)", $1, $3, CUR_POS); }
-  | expr_assert
-  ;
-
-expr_assert
-  : ASSERT expr ';' expr_assert
+  | ASSERT expr ';' expr_function
     { $$ = ATmake("Assert(<term>, <term>, <term>)", $2, $4, CUR_POS); }
+  | WITH expr ';' expr_function
+    { $$ = ATmake("With(<term>, <term>, <term>)", $2, $4, CUR_POS); }
   | expr_if
   ;
 
-- 
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