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* Prevent repeated wrapping of closed terms

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(closed(closed(closed(...)))) since this reduces performance by
  producing bigger terms and killing caching (which incidentally also
  prevents useful infinite recursion detection).
This commit is contained in:
Eelco Dolstra 2005-07-19 11:48:05 +00:00
parent 2135e7c041
commit 0f827cc607
1 changed files with 6 additions and 1 deletions
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7
src/libexpr/nixexpr.cc
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@ -233,7 +233,12 @@ Expr substitute(const ATermMap & subs, Expr e)
if (matchVar(e, name)) { if (matchVar(e, name)) {
Expr sub = subs.get(name); Expr sub = subs.get(name);
return sub ? makeClosed(sub) : e; Expr wrapped;
/* Add a "closed" wrapper around terms that aren't already
closed. The check is necessary to prevent repeated
wrapping, e.g., closed(closed(closed(...))), which kills
caching. */
return sub ? (matchClosed(sub, wrapped) ? sub : makeClosed(sub)) : e;
} }
/* In case of a function, filter out all variables bound by this /* In case of a function, filter out all variables bound by this