wroclaw-git-backups/nix
1
0
Fork 0
mirror of https://github.com/NixOS/nix synced 2025-06-26 15:51:15 +02:00
Code Activity

* In the ‘?’ operator, allow attribute paths. For instance, you can

Browse source 
write ‘attrs ? a.b’ to test whether ‘attrs’ has an attribute ‘a’
  containing an attribute ‘b’.  This is more convenient than ‘attrs ?
  a && attrs.a ? b’.

  Slight change in the semantics: it's no longer an error if the
  left-hand side of ‘?’ is not an attribute set.  In that case it just
  returns false.  So, ‘null ? foo’ no longer throws an error.
This commit is contained in:
Eelco Dolstra 2011-07-06 10:58:17 +00:00
parent 34f4b91820
commit 5637037802
4 changed files with 47 additions and 24 deletions
Download patch file Download diff file Expand all files Collapse all files

10
src/libexpr/nixexpr.hh
View file

@ -40,6 +40,12 @@ struct EvalState;
struct StaticEnv;
/* An attribute path is a sequence of attribute names. */
typedef vector<Symbol> AttrPath;
string showAttrPath(const AttrPath & attrPath);
/* Abstract syntax of Nix expressions. */
struct Expr
@ -124,8 +130,8 @@ struct ExprSelect : Expr
struct ExprOpHasAttr : Expr
{
Expr * e;
Symbol name;
ExprOpHasAttr(Expr * e, const Symbol & name) : e(e), name(name) { };
AttrPath attrPath;
ExprOpHasAttr(Expr * e, const AttrPath & attrPath) : e(e), attrPath(attrPath) { };
COMMON_METHODS
};