Substractor

test/binsub.js

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+const chai = require("chai");
+const path = require("path");
+const snarkjs = require("snarkjs");
+const compiler = require("circom");
+
+const assert = chai.assert;
+
+const bigInt = snarkjs.bigInt;
+
+function print(circuit, w, s) {
+    console.log(s + ": " + w[circuit.getSignalIdx(s)]);
+}
+
+function checkSub(_a,_b, circuit) {
+    let a=bigInt(_a);
+    let b=bigInt(_b);
+    if (a.lesser(bigInt.zero)) a = a.add(bigInt.one.shl(16));
+    if (b.lesser(bigInt.zero)) b = b.add(bigInt.one.shl(16));
+    const w = circuit.calculateWitness({a: a, b: b});
+
+    let res = a.sub(b);
+    if (res.lesser(bigInt.zero)) res = res.add(bigInt.one.shl(16));
+    assert( w[circuit.getSignalIdx("main.out")].equals(bigInt(res)) );
+}
+
+describe("BinSub test", () => {
+    let circuit;
+    before( async() => {
+        const cirDef = await compiler(path.join(__dirname, "circuits", "binsub_test.circom"));
+
+        circuit = new snarkjs.Circuit(cirDef);
+
+        console.log("NConstrains BinSub: " + circuit.nConstraints);
+    });
+
+    it("Should check variuos ege cases", async () => {
+        checkSub(0,0, circuit);
+        checkSub(1,0, circuit);
+        checkSub(-1,0, circuit);
+        checkSub(2,1, circuit);
+        checkSub(2,2, circuit);
+        checkSub(2,3, circuit);
+        checkSub(2,-1, circuit);
+        checkSub(2,-2, circuit);
+        checkSub(2,-3, circuit);
+        checkSub(-2,-3, circuit);
+        checkSub(-2,-2, circuit);
+        checkSub(-2,-1, circuit);
+        checkSub(-2,0, circuit);
+        checkSub(-2,1, circuit);
+        checkSub(-2,2, circuit);
+        checkSub(-2,3, circuit);
+    });
+
+
+});

test/circuits/binsub_test.circom

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+include "../../circuits/bitify.circom"
+include "../../circuits/binsub.circom"
+
+template A() {
+    signal private input a;
+    signal input b;
+    signal output out;
+
+    component n2ba = Num2Bits(16);
+    component n2bb = Num2Bits(16);
+    component sub = BinSub(16);
+    component b2n = Bits2Num(16);
+
+    n2ba.in <== a;
+    n2bb.in <== b;
+
+    for (var i=0; i<16; i++) {
+        sub.in[0][i] <== n2ba.out[i];
+        sub.in[1][i] <== n2bb.out[i];
+        b2n.in[i] <== sub.out[i];
+    }
+
+    out <== b2n.out;
+}
+
+component main = A();