mul.c

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/*
 * This file is part of the Fun programming language.
 * https://fun-lang.xyz/
 *
 * Copyright 2025 Johannes Findeisen <you@hanez.org>
 * Licensed under the terms of the Apache-2.0 license.
 * https://opensource.org/license/apache-2-0
 */
 
/**
 * @file mul.c
 * @brief Implements the OP_MUL opcode (numeric multiplication) in the VM.
 *
 * Handles the OP_MUL instruction, multiplying two numeric operands and
 * pushing the result. If either operand is a float, multiplication is
 * performed in double precision; otherwise it is 64-bit integer
 * multiplication.
 *
 * Behavior:
 * - Pops two values from the stack.
 * - If any operand is VAL_FLOAT, computes (double)a * (double)b and pushes a VAL_FLOAT.
 * - Else computes a.i * b.i and pushes a VAL_INT.
 *
 * Error Handling:
 * - Raises a runtime error and aborts execution if operands are not numeric.
 *
 * Example:
 * - Bytecode: OP_MUL
 * - Stack before: [3, 4]
 * - Stack after: [12]
 * - Stack before: [2.5, 4]
 * - Stack after: [10.0]
 */
 
case OP_MUL: {
  Value b = pop_value(vm);
  Value a = pop_value(vm);
  if ((a.type == VAL_INT || a.type == VAL_FLOAT) && (b.type == VAL_INT || b.type == VAL_FLOAT)) {
    if (a.type == VAL_FLOAT || b.type == VAL_FLOAT) {
      double da = (a.type == VAL_FLOAT) ? a.d : (double)a.i;
      double db = (b.type == VAL_FLOAT) ? b.d : (double)b.i;
      Value res = make_float(da * db);
      free_value(a);
      free_value(b);
      push_value(vm, res);
    } else {
      Value res = make_int(a.i * b.i);
      free_value(a);
      free_value(b);
      push_value(vm, res);
    }
  } else {
    fprintf(stderr, "Runtime type error: MUL expects numbers, got %s and %s\n",
            value_type_name(a.type), value_type_name(b.type));
    exit(1);
  }
  break;
}