From 6d782d65b74e49180ee1cc9da997116e54d8d781 Mon Sep 17 00:00:00 2001
From: Maxwell Jeffress <maxwelljeffress@proton.me>
Date: Mon, 1 Dec 2025 12:28:15 +1100
Subject: [PATCH] Add string operations

---
 README.md         | 10 +++++-----
 src/interpreter.c | 48 +++++++++++++++++++++++++++++++++++++++++++++++
 src/interpreter.h |  2 +-
 tests/string.grnd | 11 +++++++++++
 4 files changed, 65 insertions(+), 6 deletions(-)
 create mode 100644 tests/string.grnd

diff --git a/README.md b/README.md
index 6b40625..c4526b6 100644
--- a/README.md
+++ b/README.md
@@ -25,13 +25,13 @@ Progress marker:
     - [x] Labels
     - [x] Console I/O
     - [x] Control flow
-    - [ ] Data
+    - [x] Data
         - [x] Variable creation
         - [x] Variable access
-        - [ ] Lists
-            - [ ] Creation
-            - [ ] Access
-        - [ ] String operations
+        - [x] Lists
+            - [x] Creation
+            - [x] Access
+        - [x] String operations
     - [x] Maths
     - [x] Comparisions
     - [ ] Type conversions
diff --git a/src/interpreter.c b/src/interpreter.c
index b53e446..1bba766 100644
--- a/src/interpreter.c
+++ b/src/interpreter.c
@@ -696,6 +696,54 @@ void interpretGroundInstruction(GroundInstruction inst, GroundScope* scope) {
             }
             break;
         }
+        
+        /*
+         * STRING OPERATIONS 
+         * Allows easier manipulation of strings.
+         * Instructions: 
+         *    getstrcharat, getstrsize
+        */
+        case GETSTRCHARAT: {
+            if (in->args.length < 3) {
+                runtimeError(TOO_FEW_ARGS, "Expecting 3 args", in, currentInstruction);
+            }
+            if (in->args.length > 3) {
+                runtimeError(TOO_MANY_ARGS, "Expecting 3 args", in, currentInstruction);
+            }
+            if (in->args.args[0].type != VALUE && in->args.args[0].value.value.type != STRING) {
+                runtimeError(ARG_TYPE_MISMATCH, "Expecting a String for arg 1", in, currentInstruction);
+            }
+            if (in->args.args[1].type != VALUE && in->args.args[1].value.value.type != INT) {
+                runtimeError(ARG_TYPE_MISMATCH, "Expecting an Int for arg 2", in, currentInstruction);
+            }
+            if (in->args.args[2].type != DIRREF) {
+                runtimeError(ARG_TYPE_MISMATCH, "Expecting a DirectRef for arg 3", in, currentInstruction);
+            }
+            char* str = in->args.args[0].value.value.data.stringVal;
+            int64_t idx = in->args.args[1].value.value.data.intVal;
+            if (idx < strlen(str)) {
+                addVariable(scope->variables, in->args.args[2].value.refName, createCharGroundValue(str[idx]));
+            } else {
+                runtimeError(STRING_ERROR, "Out of bounds index", in, currentInstruction);
+            }
+            break;
+        }
+        case GETSTRSIZE: {
+            if (in->args.length < 2) {
+                runtimeError(TOO_FEW_ARGS, "Expecting 2 args", in, currentInstruction);
+            }
+            if (in->args.length > 2) {
+                runtimeError(TOO_MANY_ARGS, "Expecting 2 args", in, currentInstruction);
+            }
+            if (in->args.args[0].type != VALUE && in->args.args[0].value.value.type != STRING) {
+                runtimeError(ARG_TYPE_MISMATCH, "Expecting a String for arg 1", in, currentInstruction);
+            }
+            if (in->args.args[1].type != DIRREF) {
+                runtimeError(ARG_TYPE_MISMATCH, "Expecting a DirectRef for arg 2", in, currentInstruction);
+            }
+            addVariable(scope->variables, in->args.args[1].value.refName, createIntGroundValue(strlen(in->args.args[0].value.value.data.stringVal)));
+            break;
+        }
 
         /*
          * COMPARISONS
diff --git a/src/interpreter.h b/src/interpreter.h
index c0bb0ad..3c35069 100644
--- a/src/interpreter.h
+++ b/src/interpreter.h
@@ -7,7 +7,7 @@
 #include "include/uthash.h"
 
 typedef enum GroundRuntimeError {
-    ARG_TYPE_MISMATCH, TOO_FEW_ARGS, TOO_MANY_ARGS, UNKNOWN_LABEL, UNKNOWN_VARIABLE, LIST_ERROR, FIXME 
+    ARG_TYPE_MISMATCH, TOO_FEW_ARGS, TOO_MANY_ARGS, UNKNOWN_LABEL, UNKNOWN_VARIABLE, LIST_ERROR, STRING_ERROR, FIXME 
 } GroundRuntimeError;
 
 typedef struct GroundLabel {
diff --git a/tests/string.grnd b/tests/string.grnd
new file mode 100644
index 0000000..8e0b4e2
--- /dev/null
+++ b/tests/string.grnd
@@ -0,0 +1,11 @@
+input &str
+getstrsize $str &size
+set &idx 0
+@loop
+getstrcharat $str $idx &char
+println $char
+add 1 $idx &idx
+equal $idx $size &cond
+if $cond %loopend
+jump %loop
+@loopend