nordic-dev.net/nix
nordic-dev.net/nix
2
0
Fork 0
mirror of https://github.com/NixOS/nix.git synced 2024-11-01 06:40:50 +00:00
Code Issues Packages Projects Releases Wiki Activity

* Added an operator `?' to test for attribute existence, e.g.,

Browse Source 
`attrs ? x' yields true iff `attrs' has an attribute named `x'.
This commit is contained in:
Eelco Dolstra 2004-03-28 21:15:01 +00:00
parent f958bcdf1f
commit ac4d39f9db
2 changed files with 10 additions and 1 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

9
src/libexpr/eval.cc
View File

@ -288,10 +288,17 @@ Expr evalExpr2(EvalState & state, Expr e)
if (atMatch(m, e) >> "OpOr" >> e1 >> e2)
return makeBool(evalBool(state, e1) || evalBool(state, e2));
/* Attribut set update (//). */
/* Attribute set update (//). */
if (atMatch(m, e) >> "OpUpdate" >> e1 >> e2)
return updateAttrs(evalExpr(state, e1), evalExpr(state, e2));
/* Attribute existence test (?). */
if (atMatch(m, e) >> "OpHasAttr" >> e1 >> name) {
ATermMap attrs;
queryAllAttrs(evalExpr(state, e1), attrs);
return makeBool(attrs.get(name) != 0);
}
/* Barf. */
throw badTerm("invalid expression", e);
}

2
src/libexpr/parser.y
View File

@ -44,6 +44,7 @@ void yyerror(YYLTYPE * loc, yyscan_t scanner, void * data, char * s)
%nonassoc EQ NEQ
%right UPDATE
%left NEG
%nonassoc '?'
%nonassoc '~'
%%
@ -81,6 +82,7 @@ expr_op
| expr_op IMPL expr_op { $$ = ATmake("OpImpl(<term>, <term>)", $1, $3); }
| expr_op UPDATE expr_op { $$ = ATmake("OpUpdate(<term>, <term>)", $1, $3); }
| expr_op '~' expr_op { $$ = ATmake("SubPath(<term>, <term>)", $1, $3); }
| expr_op '?' ID { $$ = ATmake("OpHasAttr(<term>, <term>)", $1, $3); }
| expr_app
;