Functional Reactive Programming (FRP)

ClosureBT embraces Functional Reactive Programming principles through reactive variables and transformation pipelines. Variables are signal-based data streams that automatically propagate changes through a series of transformations.

UsePipe: Composing Transformations

UsePipe chains multiple transformation operations on a reactive variable, creating a functional pipeline where data flows from left to right through each stage:

var mousePos = UseEveryTick(MousePlaneCastPosition);

// Create a pipeline: throttle → buffer → transform
var mousePosAverage = UsePipe(mousePos,
    v => UseThrottle(0.025f, v),          // Stage 1: Sample every 25ms
    v => UseRollingBuffer(15, false, v),  // Stage 2: Keep last 15 values
    v => UseSelect(v, buffer =>           // Stage 3: Calculate average
    {
        var avg = Vector3.zero;
        foreach (var pos in buffer)
            avg += pos;
        return avg / buffer.Count;
    }));

// Result: mousePosAverage automatically updates with smoothed mouse position

var mousePos = UseEveryTick(MousePlaneCastPosition);

// Create a pipeline: throttle → buffer → transform
var mousePosAverage = UsePipe(mousePos,
    v => UseThrottle(0.025f, v),          // Stage 1: Sample every 25ms
    v => UseRollingBuffer(15, false, v),  // Stage 2: Keep last 15 values
    v => UseSelect(v, buffer =>           // Stage 3: Calculate average
    {
        var avg = Vector3.zero;
        foreach (var pos in buffer)
            avg += pos;
        return avg / buffer.Count;
    }));

// Result: mousePosAverage automatically updates with smoothed mouse position

The visualization below shows how data flows through a pipeline:

Each stage in the pipeline transforms the incoming data stream:

• Source: The origin of data (e.g., mouse position, sensor input)
• Throttle: Limits update frequency to prevent excessive computations
• Buffer: Collects multiple values for aggregate operations
• Select/Transform: Maps values to new forms (like LINQ's Select)

Use Methods: Reactive Operators

ClosureBT provides a library of Use* methods for building reactive pipelines. These are similar to RxJS operators or LINQ methods, designed for composing reactive data flows:

var mousePos = UseEveryTick(MouseWorldPosition);
var health = UseEveryTick(() => player.health);

var mousePos = UseEveryTick(MouseWorldPosition);
var health = UseEveryTick(() => player.health);

var mousePos = UseEveryTick(MousePosition);
var throttled = UseThrottle(0.1f, mousePos); // Max once per 100ms

var mousePos = UseEveryTick(MousePosition);
var throttled = UseThrottle(0.1f, mousePos); // Max once per 100ms

var positions = UseRollingBuffer(10, false, mousePos);
// positions.Value is a List<Vector3> with last 10 positions

var positions = UseRollingBuffer(10, false, mousePos);
// positions.Value is a List<Vector3> with last 10 positions

var health = UseEveryTick(() => player.health);
var healthPercent = UseSelect(health, h => h / 100f);

var health = UseEveryTick(() => player.health);
var healthPercent = UseSelect(health, h => h / 100f);

var target = UseEveryTick(() => currentTarget);
var targetChanged = UseValueDidChange(target);

OnTick(() => {
    if (targetChanged.Value)
        Debug.Log("New target acquired!");
});

var target = UseEveryTick(() => currentTarget);
var targetChanged = UseValueDidChange(target);

OnTick(() => {
    if (targetChanged.Value)
        Debug.Log("New target acquired!");
});

var isMoving = UseEveryTick(() => velocity.magnitude > 0.1f);
var movingDuration = UseTimePredicateElapsed(isMoving, _ => isMoving.Value);
// movingDuration.Value = seconds the entity has been moving

var isMoving = UseEveryTick(() => velocity.magnitude > 0.1f);
var movingDuration = UseTimePredicateElapsed(isMoving, _ => isMoving.Value);
// movingDuration.Value = seconds the entity has been moving

Complete Use Methods Reference

All available reactive operators in ClosureBT: