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/**************************************************************************/
/* */
/* The Why platform for program certification */
/* */
/* Copyright (C) 2002-2011 */
/* */
/* Jean-Christophe FILLIATRE, CNRS & Univ. Paris-sud 11 */
/* Claude MARCHE, INRIA & Univ. Paris-sud 11 */
/* Yannick MOY, Univ. Paris-sud 11 */
/* Romain BARDOU, Univ. Paris-sud 11 */
/* */
/* Secondary contributors: */
/* */
/* Thierry HUBERT, Univ. Paris-sud 11 (former Caduceus front-end) */
/* Nicolas ROUSSET, Univ. Paris-sud 11 (on Jessie & Krakatoa) */
/* Ali AYAD, CNRS & CEA Saclay (floating-point support) */
/* Sylvie BOLDO, INRIA (floating-point support) */
/* Jean-Francois COUCHOT, INRIA (sort encodings, hyps pruning) */
/* Mehdi DOGGUY, Univ. Paris-sud 11 (Why GUI) */
/* */
/* This software is free software; you can redistribute it and/or */
/* modify it under the terms of the GNU Lesser General Public */
/* License version 2.1, with the special exception on linking */
/* described in file LICENSE. */
/* */
/* This software is distributed in the hope that it will be useful, */
/* but WITHOUT ANY WARRANTY; without even the implied warranty of */
/* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. */
/* */
/**************************************************************************/
//@+ CheckArithOverflow = no
//@ logic integer sqr(integer x) = x * x;
class Isqrt {
/*@ requires x >= 0;
@ ensures \result >= 0 && sqr(\result) <= x && x < sqr(\result + 1);
@*/
static int isqrt(int x) {
int count = 0, sum = 1;
/*@ loop_invariant count >= 0 && x >= sqr(count) && sum == sqr(count+1);
@ loop_variant x - count;
@*/
while (sum <= x) sum += 2 * ++count + 1;
return count;
}
//@ ensures \result == 4;
static int main () {
int r;
r = isqrt(17);
//@ assert r < 4 ==> false;
//@ assert r > 4 ==> false;
return r;
}
}
/*
Local Variables:
compile-command: "make Isqrt.why3ml"
End:
*/
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