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* Change the semantics of "with" so that inner "withs" take 

precedence, i.e. `with {x=1;}; with {x=2;}; x' evaluates to 2'.
  This has a simpler implementation and seems more natural.  There
  doesn't seem to be any code in Nixpkgs or NixOS that relies on the
  old behaviour.
This commit is contained in:
Eelco Dolstra 2010-04-14 08:37:08 +00:00
parent 816f9c0f6f
commit 85d13c8f93
2 changed files with 2 additions and 25 deletions
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25
src/libexpr/eval.cc
View File

@ -232,19 +232,6 @@ void mkPath(Value & v, const char * s)
}
Value * EvalState::lookupWith(Env * env, const Symbol & name)
{
if (!env) return 0;
Value * v = lookupWith(env->up, name);
if (v) return v;
Bindings::iterator i = env->bindings.find(sWith);
if (i == env->bindings.end()) return 0;
Bindings::iterator j = i->second.attrs->find(name);
if (j != i->second.attrs->end()) return &j->second;
return 0;
}
Value * EvalState::lookupVar(Env * env, const Symbol & name)
{
/* First look for a regular variable binding for `name'. */
@ -254,22 +241,14 @@ Value * EvalState::lookupVar(Env * env, const Symbol & name)
}
/* Otherwise, look for a `with' attribute set containing `name'.
Outer `withs' take precedence (i.e. `with {x=1;}; with {x=2;};
x' evaluates to 1). */
Value * v = lookupWith(env, name);
if (v) return v;
/* Alternative implementation where the inner `withs' take
precedence (i.e. `with {x=1;}; with {x=2;}; x' evaluates to
2). */
#if 0
Inner `withs' take precedence (i.e. `with {x=1;}; with {x=2;};
x' evaluates to 2). */
for (Env * env2 = env; env2; env2 = env2->up) {
Bindings::iterator i = env2->bindings.find(sWith);
if (i == env2->bindings.end()) continue;
Bindings::iterator j = i->second.attrs->find(name);
if (j != i->second.attrs->end()) return &j->second;
}
#endif
throwEvalError("undefined variable `%1%'", name);
}

2
src/libexpr/eval.hh
View File

@ -240,8 +240,6 @@ private:
Value * lookupVar(Env * env, const Symbol & name);
Value * lookupWith(Env * env, const Symbol & name);
friend class ExprVar;
friend class ExprAttrs;
friend class ExprLet;