Fix exponential time behaviour when constructing Alt (#106)

fangyi-zhou · web-flow · commit 60f476a7d092 · 2021-12-03T15:46:23.000-06:00
Fixes #97 by removing a duplicate evaluation Signed-off-by: Fangyi Zhou <fangyi.zhou15@imperial.ac.uk>
diff --git a/src/syntax/sedlex.ml b/src/syntax/sedlex.ml
@@ -38,7 +38,7 @@ let alt r1 r2 succ =
   | Some c1, Some c2 -> chars (Cset.union c1 c2) succ
   | _ ->
     let n = new_node () in
-    n.eps <- [r1 succ; r2 succ];
+    n.eps <- [nr1; nr2];
     n
 
 let rep r succ =

Original file line number	Diff line number	Diff line change
`@@ -38,7 +38,7 @@ let alt r1 r2 succ =`
`38`	`38`	`\| Some c1, Some c2 -> chars (Cset.union c1 c2) succ`
`39`	`39`	`\| _ ->`
`40`	`40`	`let n = new_node () in`
`41`		`- n.eps <- [r1 succ; r2 succ];`
	`41`	`+ n.eps <- [nr1; nr2];`
`42`	`42`	`n`
`43`	`43`
`44`	`44`	`let rep r succ =`