How do that use uniform and mx_noise_float?

Questions
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1

this._deltaTime = uniform(float());
const boidSpeed = uniform(3); // defined

this.computePosition = Fn(()=>{
const boid_pos = positionStorage.element(instanceIndex).toVar();
const boid_dir = directionStorage.element(instanceIndex).toVar();
const noise_offset = noiseStorage.element(instanceIndex).toVar();
const tempVec2 = boid_pos.mul(time.div(100.).add(noise_offset));

        const noise =mx_noise_float(boid_pos.mul(time.div(100.).add(noise_offset))).add(1.0).div(2.0).toVar();

// that velocity how to use noise ,use addAssign while report error ,add will to
const velocity = boidSpeed.mul(float(10).add(sin(time))).toVar();
// i want use this
//eg :const velocity = boidSpeed.mul(float(10).mul(sin(time)).add(noise)).toVar() or
//eg: velocity.addAssign(noise)

        boid_pos.addAssign(boid_dir.mul(velocity).mul(this._deltaTime));
        positionStorage.element(instanceIndex).assign(boid_pos);
    })().compute(_times_);