logos-blockchain-circuits/misc/comparator.circom

//test
pragma circom 2.1.9;

include "../circomlib/circuits/bitify.circom";
include "../circomlib/circuits/comparators.circom";

// If a or b isn't guaranteed to be less than p use SafeFullComparator
// See https://www.notion.so/nomos-tech/Comparisons-1fd261aa09df81feae1ff3e6612b92a0

template SafeFullLessThan() {
    signal input a;
    signal input b;
    signal output out;

    component bitifier_a = Num2Bits_strict();
    component bitifier_b = Num2Bits_strict();

    bitifier_a.in <== a;
    bitifier_b.in <== b;

    component numifier_a = Bits2Num(252);
    component numifier_b = Bits2Num(252);

    for(var i =0; i<252; i++){
        numifier_a.in[i] <== bitifier_a.out[i+2];
        numifier_b.in[i] <== bitifier_b.out[i+2];
    }

    component A = LessThan(252);
    A.in[0] <== numifier_b.out;
    A.in[1] <== numifier_a.out;

    component B = IsEqual();
    B.in[0] <== numifier_a.out;
    B.in[1] <== numifier_b.out;

    component C = IsEqual();
    C.in[0] <== bitifier_a.out[1];
    C.in[1] <== bitifier_b.out[1];

    component D = IsEqual();
    D.in[0] <== bitifier_a.out[1];
    D.in[1] <== 1;

    component E = IsEqual();
    E.in[0] <== bitifier_a.out[0];
    E.in[1] <== bitifier_b.out[0];

    component F = IsEqual();
    F.in[0] <== bitifier_a.out[0];
    F.in[1] <== 1;

    signal intermediate_results[4];
    intermediate_results[0] <== (1 - C.out) * (1-D.out);
    intermediate_results[1] <== (1 - C.out) * (1-E.out);
    intermediate_results[2] <== intermediate_results[1] * (1- F.out);
    intermediate_results[3] <== B.out * (intermediate_results[0] + intermediate_results[2]);

    out <== (1 - A.out) * ((1 - B.out) + intermediate_results[3]);
}

// Safely compare two n-bit numbers 
// Performs range checks on the inputs to avoid overflow. Range is n <= 252
template SafeLessThan(n) {
    assert(n <= 252);
    signal input in[2];
    signal output out;

    component aInRange = Num2Bits(n);
    aInRange.in <== in[0];
    component bInRange = Num2Bits(n);
    bInRange.in <== in[1];

    component lt = LessThan(n);

    lt.in[0] <== in[0];
    lt.in[1] <== in[1];

    out <== lt.out;
}