o1js/dist/node/lib/provable/core/exists.js

TypeScript framework for zk-SNARKs and zkApps

import { Snarky } from '../../../bindings.js';
import { FieldConst } from './fieldvar.js';
import { MlArray, MlOption } from '../../ml/base.js';
import { createField } from './field-constructor.js';
import { TupleN } from '../../util/types.js';
export { createVarField, exists, existsAsync, existsOne };
/**
 * Witness `size` field element variables by passing a callback that returns `size` bigints.
 *
 * Note: this is called "exists" because in a proof, you use it like this:
 * > "I prove that there exists x, such that (some statement)"
 */
function exists(size, compute) {
    // enter prover block
    let finish = Snarky.run.enterAsProver(size);
    if (!Snarky.run.inProver()) {
        // step outside prover block and create vars: compile case
        let vars = MlArray.mapFrom(finish(MlOption()), createVarField);
        return TupleN.fromArray(size, vars);
    }
    // run the callback to get values to witness
    let values = compute();
    if (values.length !== size)
        throw Error(`Expected witnessed values of length ${size}, got ${values.length}.`);
    // note: here, we deliberately reduce the bigint values modulo the field size
    // this makes it easier to use normal arithmetic in low-level gadgets,
    // i.e. you can just witness x - y and it will be a field subtraction
    let inputValues = MlArray.mapTo(values, FieldConst.fromBigint);
    // step outside prover block and create vars: prover case
    let fieldVars = finish(MlOption(inputValues));
    let vars = MlArray.mapFrom(fieldVars, createVarField);
    return TupleN.fromArray(size, vars);
}
/**
 * Variant of {@link exists} that witnesses 1 field element.
 */
function existsOne(compute) {
    return exists(1, () => [compute()])[0];
}
/**
 * Async variant of {@link exists}, which allows an async callback.
 */
async function existsAsync(size, compute) {
    // enter prover block
    let finish = Snarky.run.enterAsProver(size);
    if (!Snarky.run.inProver()) {
        let vars = MlArray.mapFrom(finish(MlOption()), createVarField);
        return TupleN.fromArray(size, vars);
    }
    // run the async callback to get values to witness
    let values = await compute();
    if (values.length !== size)
        throw Error(`Expected witnessed values of length ${size}, got ${values.length}.`);
    // note: here, we deliberately reduce the bigint values modulo the field size
    // this makes it easier to use normal arithmetic in low-level gadgets,
    // i.e. you can just witness x - y and it will be a field subtraction
    let inputValues = MlArray.mapTo(values, FieldConst.fromBigint);
    let fieldVars = finish(MlOption(inputValues));
    let vars = MlArray.mapFrom(fieldVars, createVarField);
    return TupleN.fromArray(size, vars);
}
// helpers for varfields
function createVarField(x) {
    return createField(x);
}
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