From cbcf142f5760a365614003a2c1c5ab20277ddd7f Mon Sep 17 00:00:00 2001
From: David Wilson <david@daviwil.com>
Date: Thu, 17 Mar 2022 18:59:32 +0200
Subject: [PATCH] language: Add modulo `%` operator that works on integers

---
 src/compiler.c |  3 +++
 src/disasm.c   |  2 ++
 src/op.h       |  1 +
 src/scanner.c  |  2 ++
 src/scanner.h  |  1 +
 src/vm.c       | 10 ++++++++++
 6 files changed, 19 insertions(+)

diff --git a/src/compiler.c b/src/compiler.c
index 6d6e6f3..b4f8528 100644
--- a/src/compiler.c
+++ b/src/compiler.c
@@ -953,6 +953,9 @@ static void compiler_parse_operator_call(CompilerContext *ctx, Token *call_token
   case TokenKindSlash:
     compiler_emit_byte(ctx, OP_DIVIDE);
     break;
+  case TokenKindPercent:
+    compiler_emit_byte(ctx, OP_MODULO);
+    break;
   case TokenKindAnd:
     compiler_emit_byte(ctx, OP_AND);
     break;
diff --git a/src/disasm.c b/src/disasm.c
index 1b88b75..f972386 100644
--- a/src/disasm.c
+++ b/src/disasm.c
@@ -72,6 +72,8 @@ int mesche_disasm_instr(Chunk *chunk, int offset) {
     return mesche_disasm_simple_instr("OP_MULTIPLY", offset);
   case OP_DIVIDE:
     return mesche_disasm_simple_instr("OP_DIVIDE", offset);
+  case OP_MODULO:
+    return mesche_disasm_simple_instr("OP_MODULO", offset);
   case OP_NEGATE:
     return mesche_disasm_simple_instr("OP_NEGATE", offset);
   case OP_AND:
diff --git a/src/op.h b/src/op.h
index 91dc507..f05b4c5 100644
--- a/src/op.h
+++ b/src/op.h
@@ -13,6 +13,7 @@ typedef enum {
   OP_SUBTRACT,
   OP_MULTIPLY,
   OP_DIVIDE,
+  OP_MODULO,
   OP_NEGATE, // TODO: Remove in favor of SUBTRACT!
   OP_AND,
   OP_OR,
diff --git a/src/scanner.c b/src/scanner.c
index 37b5081..4a5c2c0 100644
--- a/src/scanner.c
+++ b/src/scanner.c
@@ -320,6 +320,8 @@ Token mesche_scanner_next_token(Scanner *scanner) {
     return scanner_make_token(scanner, TokenKindStar);
   case '/':
     return scanner_make_token(scanner, TokenKindSlash);
+  case '%':
+    return scanner_make_token(scanner, TokenKindPercent);
   case '>': {
     if (scanner_peek(scanner) == '=') {
       scanner_next_char(scanner);
diff --git a/src/scanner.h b/src/scanner.h
index 8ad9597..ca5e323 100644
--- a/src/scanner.h
+++ b/src/scanner.h
@@ -21,6 +21,7 @@ typedef enum {
   TokenKindMinus,
   TokenKindStar,
   TokenKindSlash,
+  TokenKindPercent,
   TokenKindAnd,
   TokenKindOr,
   TokenKindNot,
diff --git a/src/vm.c b/src/vm.c
index bd02904..b7b08a0 100644
--- a/src/vm.c
+++ b/src/vm.c
@@ -751,6 +751,16 @@ InterpretResult mesche_vm_run(VM *vm) {
     case OP_DIVIDE:
       BINARY_OP(NUMBER_VAL, IS_NUMBER, AS_NUMBER, /);
       break;
+    case OP_MODULO: {
+      if (!IS_NUMBER(vm_stack_peek(vm, 0)) || !IS_NUMBER(vm_stack_peek(vm, 1))) {
+        vm_runtime_error(vm, "Operands must be numbers.");
+        return INTERPRET_RUNTIME_ERROR;
+      }
+      int b = (int)AS_NUMBER(mesche_vm_stack_pop(vm));
+      int a = (int)AS_NUMBER(mesche_vm_stack_pop(vm));
+      mesche_vm_stack_push(vm, NUMBER_VAL(a % b));
+      break;
+    }
     case OP_AND:
       BINARY_OP(BOOL_VAL, IS_ANY, AS_BOOL, &&);
       break;