isqrt.c

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/*
 * This file is part of the Fun programming language.
 * https://fun-lang.xyz/
 *
 * Copyright 2026 Johannes Findeisen <you@hanez.org>
 * Licensed under the terms of the Apache-2.0 license.
 * https://opensource.org/license/apache-2-0
 */


case OP_ISQRT: {
 Value v = pop_value(vm);
 if (!((v.type == VAL_INT) || (v.type == VAL_FLOAT))) {
 fprintf(stderr, "Runtime type error: ISQRT expects number, got %s\n", value_type_name(v.type));
 exit(1);
 }
 int64_t a = (v.type == VAL_INT) ? v.i : (int64_t)v.d;
 if (a <= 0) {
 free_value(v);
 push_value(vm, make_int(0));
 break;
 }
 /* Binary isqrt inline */
 uint64_t n = (uint64_t)a;
 uint64_t x = 0;
 uint64_t bit = (uint64_t)1 << 62; /* highest even bit set */
 while (bit > n)
 bit >>= 2;
 while (bit != 0) {
 if (n >= x + bit) {
 n -= x + bit;
 x = (x >> 1) + bit;
 } else {
 x >>= 1;
 }
 bit >>= 2;
 }
 int64_t r = (int64_t)x;
 free_value(v);
 push_value(vm, make_int(r));
 break;
}