From c1d28086339ea0c7ca8ccf2cd7431cf7a4fa7ec7 Mon Sep 17 00:00:00 2001
From: James <101812526+WoodchuckXL@users.noreply.github.com>
Date: Wed, 17 Jun 2026 14:41:55 -0400
Subject: [PATCH] Fix string negative indexing

---
 src/classes/strng.c          | 17 ++++++++++++++++-
 test/string/index_neg.morpho |  5 +++++
 2 files changed, 21 insertions(+), 1 deletion(-)
 create mode 100644 test/string/index_neg.morpho

diff --git a/src/classes/strng.c b/src/classes/strng.c
index 2d1ca699..70bbaf02 100644
--- a/src/classes/strng.c
+++ b/src/classes/strng.c
@@ -176,6 +176,7 @@ int string_countchars(objectstring *s) {
 
 /** Get a pointer to the i'th character of a string */
 char *string_index(objectstring *s, int i) {
+    if (i<0) return NULL;
     int n=0;
     for (char *c = s->string; *c!='\0'; ) {
         if (i==n) return (char *) c;
@@ -219,6 +220,20 @@ value String_clone(vm *v, int nargs, value *args) {
     return out;
 }
 
+/** Gets a specified character from a string */
+value String_getindex(vm *v, int nargs, value *args) {
+    objectstring *slf = MORPHO_GETSTRING(MORPHO_SELF(args));
+    value out=MORPHO_NIL;
+    int n=MORPHO_GETINTEGERVALUE(MORPHO_GETARG(args, 0));
+
+    char *c = string_index(slf, n);
+    if (c) {
+        out=object_stringfromcstring(c, morpho_utf8numberofbytes(c));
+        morpho_bindobjects(v, 1, &out);
+    } else morpho_runtimeerror(v, VM_OUTOFBOUNDS);
+    return out;
+}
+
 /** Enumerate members of a string */
 value String_enumerate(vm *v, int nargs, value *args) {
     objectstring *slf = MORPHO_GETSTRING(MORPHO_SELF(args));
@@ -292,7 +307,7 @@ MORPHO_BEGINCLASS(String)
 MORPHO_METHOD_SIGNATURE(MORPHO_COUNT_METHOD, "Int ()", String_count, MORPHO_FN_PUREFN),
 MORPHO_METHOD_SIGNATURE(MORPHO_PRINT_METHOD, "String ()", String_print, MORPHO_FN_IO),
 MORPHO_METHOD_SIGNATURE(MORPHO_CLONE_METHOD, "String ()", String_clone, MORPHO_FN_PUREFN|MORPHO_FN_ALLOCATES),
-MORPHO_METHOD_SIGNATURE(MORPHO_GETINDEX_METHOD, "(Int)", String_enumerate, MORPHO_FN_THROWS),
+MORPHO_METHOD_SIGNATURE(MORPHO_GETINDEX_METHOD, "String (Int)", String_getindex, MORPHO_FN_THROWS),
 MORPHO_METHOD_SIGNATURE(MORPHO_GETINDEX_METHOD, "Nil (...)", String_enumerate__err, MORPHO_FN_THROWS),
 MORPHO_METHOD_SIGNATURE(MORPHO_ENUMERATE_METHOD, "(Int)", String_enumerate, MORPHO_FN_THROWS),
 MORPHO_METHOD_SIGNATURE(MORPHO_ENUMERATE_METHOD, "Nil (...)", String_enumerate__err, MORPHO_FN_THROWS),
diff --git a/test/string/index_neg.morpho b/test/string/index_neg.morpho
new file mode 100644
index 00000000..c58dee6e
--- /dev/null
+++ b/test/string/index_neg.morpho
@@ -0,0 +1,5 @@
+var s = "Hello"
+
+print s[-1]
+// expect Error 'IndxBnds'
+