circomlib/circuits/comparators.circom
2019-07-08 14:08:04 +02:00

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/*
Copyright 2018 0KIMS association.
This file is part of circom (Zero Knowledge Circuit Compiler).
circom is a free software: you can redistribute it and/or modify it
under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.
circom 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. See the GNU General Public
License for more details.
You should have received a copy of the GNU General Public License
along with circom. If not, see <https://www.gnu.org/licenses/>.
*/
include "bitify.circom";
include "binsum.circom";
template IsZero() {
signal input in;
signal output out;
signal inv;
inv <-- in!=0 ? 1/in : 0;
out <== -in*inv +1;
in*out === 0;
}
template IsEqual() {
signal input in[2];
signal output out;
component isz = IsZero();
in[1] - in[0] ==> isz.in;
isz.out ==> out;
}
template ForceEqualIfEnabled() {
signal input enabled;
signal input in[2];
component isz = IsZero();
in[1] - in[0] ==> isz.in;
(1 - isz.out)*enabled === 0;
}
/*
// N is the number of bits the input have.
// The MSF is the sign bit.
template LessThan(n) {
signal input in[2];
signal output out;
component num2Bits0;
component num2Bits1;
component adder;
adder = BinSum(n, 2);
num2Bits0 = Num2Bits(n);
num2Bits1 = Num2BitsNeg(n);
in[0] ==> num2Bits0.in;
in[1] ==> num2Bits1.in;
var i;
for (i=0;i<n;i++) {
num2Bits0.out[i] ==> adder.in[0][i];
num2Bits1.out[i] ==> adder.in[1][i];
}
adder.out[n-1] ==> out;
}
*/
template LessThan(n) {
signal input in[2];
signal output out;
component n2b = Num2Bits(n*2+1);
n2b.in <== in[0]+ (1<<n) - in[1];
out <== 1-n2b.out[n];
}
// N is the number of bits the input have.
// The MSF is the sign bit.
template LessEqThan(n) {
signal input in[2];
signal output out;
component lt = LessThan(n);
lt.in[0] <== in[0];
lt.in[1] <== in[1]+1;
lt.out ==> out;
}
// N is the number of bits the input have.
// The MSF is the sign bit.
template GreaterThan(n) {
signal input in[2];
signal output out;
component lt = LessThan(n);
lt.in[0] <== in[1];
lt.in[1] <== in[0];
lt.out ==> out;
}
// N is the number of bits the input have.
// The MSF is the sign bit.
template GreaterEqThan(n) {
signal input in[2];
signal output out;
component lt = LessThan(n);
lt.in[0] <== in[1];
lt.in[1] <== in[0]+1;
lt.out ==> out;
}