From 71cab59a89426890a22a5e42e9f538683a9547bc Mon Sep 17 00:00:00 2001
From: Aadhavan Srinivasan <aadhavan@twomorecents.org>
Date: Thu, 12 Dec 2024 14:49:45 -0500
Subject: [PATCH] Got rid of unnecessary special case to match at end-of-string
Instead, I tweaked the rest of the matching function, so that a special
check isn't necessary. If we are trying to match at the end of a string,
we skip any of the actual matching and proceed straight to finding
0-length matches.
This change was made because, with the special case, capturing groups
weren't getting updated if we had an end-of-string match.
---
matching.go | 22 ++--------------------
1 file changed, 2 insertions(+), 20 deletions(-)
diff --git a/matching.go b/matching.go
index 83e7f04..fc87b6e 100644
--- a/matching.go
+++ b/matching.go
@@ -60,8 +60,7 @@ func (g Group) isValid() bool {
// takeZeroState takes the 0-state (if such a transition exists) for all states in the
// given slice. It returns the resulting states. If any of the resulting states is a 0-state,
// the second ret val is true.
-// The third ret val is a list of all the group numbers of all the opening parentheses we crossed,
-// and the fourth is a list of all the closing parentheses we passed
+// If a state begins or ends a capturing group, its 'thread' is updated to contain the correct index.
func takeZeroState(states []*State, numGroups int, idx int) (rtv []*State, isZero bool) {
for _, state := range states {
if len(state.transitions[EPSILON]) > 0 {
@@ -169,23 +168,6 @@ func findAllMatchesHelper(start *State, str []rune, offset int, numGroups int) (
// The second value here shouldn't be used, because we should exit when the third return value is > than len(str)
return false, []Group{}, offset
}
- // 'Base case' - if we are at the end of the string, check if we can add a zero-length match
- if offset == len(str) {
- // Get all zero-state matches. If we can get to a zero-state without matching anything, we
- // can add a zero-length match. This is all true only if the start state itself matches nothing.
- // TODO - fill in capturing groups for these matches
- if start.isEmpty {
- to_return := newMatch(numGroups + 1)
- if start.groupBegin {
- to_return[start.groupNum].startIdx = offset
- }
- if ok := zeroMatchPossible(str, offset, numGroups, start); ok {
- to_return[0] = Group{offset, offset}
- return true, to_return, offset + 1
- }
- }
- return false, []Group{}, offset + 1
- }
// Hold a list of match indices for the current run. When we
// can no longer find a match, the match with the largest range is
@@ -366,7 +348,7 @@ func findAllMatchesHelper(start *State, str []rune, offset int, numGroups int) (
for _, state := range currentStates {
// Only add the match if the start index is in bounds. If the state has an assertion,
// make sure the assertion checks out.
- if state.isLast && startIdx < len(str) {
+ if state.isLast && i <= len(str) {
if state.assert == NONE || state.checkAssertion(str, i) {
for j := 1; j < numGroups+1; j++ {
tempIndices[j] = state.threadGroups[j]