Make optimizations based on the purity of predicates.

This allows something like

    $ ./bfs -empty -false

to avoid evaluating -empty, just like find.

1 files changed, 6 insertions, 2 deletions

diff --git a/bfs.h b/bfs.h
index c9b248d..b365a53 100644
--- a/bfs.h
+++ b/bfs.h
@@ -111,12 +111,13 @@ enum timeunit {
 };
 
 struct expr {
+	/** The function that evaluates this expression. */
+	eval_fn *eval;
+
 	/** The left hand side of the expression. */
 	struct expr *lhs;
 	/** The right hand side of the expression. */
 	struct expr *rhs;
-	/** The function that evaluates this expression. */
-	eval_fn *eval;
 
 	/** The optional comparison flag. */
 	enum cmpflag cmp;
@@ -138,6 +139,9 @@ struct expr {
 
 	/** Optional string data for this expression. */
 	const char *sdata;
+
+	/** Whether this expression has no side effects. */
+	bool pure;
 };
 
 /**