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* Added syntactic sugar to the construction of attribute sets to

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`inherit' variables from the surrounding lexical scope.

  E.g.,

    {stdenv, libfoo}: derivation {
      builder = ./bla;
      inherit stdenv libfoo;
      xyzzy = 1;
    }

  is equivalent to

    {stdenv, libfoo}: derivation {
      builder = ./bla;
      stdenv = stdenv;
      libfoo = libfoo;
      xyzzy = 1;
    }

  Note that for mutually recursive attribute set definitions (`rec
  {...}'), this also works, that is, `rec {inherit x;}' is equivalent
  to `let {fresh = x; body = rec {x = fresh;};}', *not*
  `rec {x = x}'.
This commit is contained in:
Eelco Dolstra 2004-02-02 21:39:33 +00:00
parent d9f30fe7c7
commit 1c9c0a5a46
6 changed files with 78 additions and 41 deletions
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20
src/libexpr/parser.y
View file

@ -18,6 +18,7 @@
void setParseResult(void * data, ATerm t);
void parseError(void * data, char * error, int line, int column);
ATerm absParsedPath(void * data, ATerm t);
ATerm fixAttrs(int recursive, ATermList as);
void yyerror(YYLTYPE * loc, yyscan_t scanner, void * data, char * s)
{
@ -33,9 +34,9 @@ void yyerror(YYLTYPE * loc, yyscan_t scanner, void * data, char * s)
%type <t> start expr expr_function expr_assert expr_op
%type <t> expr_app expr_select expr_simple bind formal
%type <ts> binds expr_list formals
%type <ts> binds ids expr_list formals
%token <t> ID INT STR PATH URI
%token IF THEN ELSE ASSERT LET REC EQ NEQ AND OR IMPL
%token IF THEN ELSE ASSERT LET REC INHERIT EQ NEQ AND OR IMPL
%nonassoc IMPL
%left OR
@ -90,9 +91,14 @@ expr_simple
| PATH { $$ = ATmake("Path(<term>)", absParsedPath(data, $1)); }
| URI { $$ = ATmake("Uri(<term>)", $1); }
| '(' expr ')' { $$ = $2; }
| LET '{' binds '}' { $$ = ATmake("LetRec(<term>)", $3); }
| REC '{' binds '}' { $$ = ATmake("Rec(<term>)", $3); }
| '{' binds '}' { $$ = ATmake("Attrs(<term>)", $2); }
/* Let expressions `let {..., body = ...}' are just desugared
into `(rec {..., body = ...}).body'. */
| LET '{' binds '}'
{ $$ = ATmake("Select(<term>, \"body\")", fixAttrs(1, $3)); }
| REC '{' binds '}'
{ $$ = fixAttrs(1, $3); }
| '{' binds '}'
{ $$ = fixAttrs(0, $2); }
| '[' expr_list ']' { $$ = ATmake("List(<term>)", $2); }
| IF expr THEN expr ELSE expr
{ $$ = ATmake("If(<term>, <term>, <term>)", $2, $4, $6); }
@ -106,8 +112,12 @@ binds
bind
: ID '=' expr ';'
{ $$ = ATmake("Bind(<term>, <term>)", $1, $3); }
| INHERIT ids ';'
{ $$ = ATmake("Inherit(<term>)", $2); }
;
ids: ids ID { $$ = ATinsert($1, $2); } | { $$ = ATempty; };
expr_list
: expr_select expr_list { $$ = ATinsert($2, $1); }
/* yes, this is right-recursive, but it doesn't matter since