• Donald A Norman. Cognitive engineering. 1986.

• Live Programming
• Programming by Example

Difficult for generic imperative applications!

Proposed Solution

• A domain-specific programming environment for programming GUI applications
• Enforce functional rendering

var i = 23;

function view() {
  return (<div>
    <p>Count: {i}</p>
    <button onclick={inc}>
      Increment
    </button>
  </div>);
}

function inc() {
  i++;
}

• Model holds entire application state
• View generates visible output based on Model
• Update processes events and changes the Model

Many other approaches and implementations

• Elm, Flux, Redux, Cycle.js

Functional Rendering for live programming

• Burckhardt, Fahndrich, de Halleux, McDirmid, Moskal, Tillmann and Kato. It’s Alive! Continuous Feedback in UI Programming. PLDI ’13.

Live code updates to stateful applications with continous feedback

• Changing the program code at runtime
• Keep application state
• Continous feedback
  • Re-evaluate expressions, re-render output, etc.

Input-output examples for synthesizing
human-readable program code

• Source code remains canonical representation of program

Live Program Synthesis of View function

view : Model -> Output

• Current model at runtime used as input
• User creates output example by direct manipulation of GUI
• Repair current view according to input-output example

Changes to constants

Inverting basic operators, gradient descent

• Galenson, Reames, Bodik, Hartmann, Sen. Programmatic and Direct Manipulation, Together at Last. PLDI ’16.

• Formal specification of design space
• Purity of View function enforced either statically or dynamically