Example

const { monad: optionMonad, none, some } = await import("./option.js");

const optionA = some(1);
const optionB = some(2);
const optionC = some(3);

const computation = doT(optionMonad)
    .addM("a", optionA)
    .addM("b", optionB)
    .addWith("bSquared", ({ b }) => b * b)
    .addM("c", optionC);

expect(
    computation
        .addMWith("cSqrt", ({ c }) => {
            const sqrt = Math.sqrt(c);
            return Number.isInteger(sqrt) ? some(sqrt) : none();
        })
        .finish(({ bSquared, cSqrt }) => bSquared + cSqrt),
).toStrictEqual(
    none(),
);

const result = computation.finish(({ a, b, c }) => a + b + c);
expect(result).toStrictEqual(some(6));
Copy