set.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 set.c
 * @brief Implements the OP_SET opcode for setting elements in arrays in the VM.
 *
 * Handles the OP_SET instruction, which sets a value at a specified index in an array.
 * The value, index, and array are popped from the stack; the value is returned back
 * on the stack (as a copy) to mirror expression semantics.
 *
 * Behavior:
 * - Pops the value, index, and array from the stack.
 * - Sets the value at the specified index in the array.
 * - Pushes a copy of the value back onto the stack.
 *
 * Error Handling:
 * - Exits with a runtime error if the array or index is of the wrong type.
 * - Exits with a runtime error if the index is out of bounds.
 *
 * Example:
 * - Bytecode: OP_SET
 * - Stack before: [42, 1, [10, 20, 30]]
 * - Stack after: [42]
 */
 
case OP_SET: {
  Value v = pop_value(vm);
  Value idx = pop_value(vm);
  Value arr = pop_value(vm);
  if (arr.type != VAL_ARRAY || idx.type != VAL_INT) {
    fprintf(stderr, "Runtime type error: ARR_SET expects (array, int, value)\n");
    exit(1);
  }
  if (!array_set(&arr, (int)idx.i, v)) {
    fprintf(stderr, "Runtime error: set index out of range\n");
    exit(1);
  }
  free_value(arr);
  free_value(idx);
  /* v already owned by array; push copy for return value */
  push_value(vm, copy_value(&v));
  free_value(v);
  break;
}