Koko Muroya edited this page Jan 17, 2018 · 2 revisions

dGoI Visualiser

A tool for web browsers (http://koko-m.github.io/GoI-Visualiser/) that simulates execution of the dynamic GoI abstract machine for the lambda-calculus.

What is the dynamic GoI abstract machine?

Given the graph representation of an untyped lambda-term, the dynamic GoI abstract machine simulates its evaluation by token-guided graph rewriting. An agent called "token" moves around the graph and triggers rewrites, using its own data. The machine can simulate three evaluation strategies: namely, call-by-need, left-to-right call-by-value, and right-to-left call-by-value.


  1. Select an example, or enter your own closed lambda-term.
  2. Select an evaluation strategy, or click the >> button if you are happy with the current strategy.
  3. Click the button.

Un-checking the Draw button stops drawing graphs. An execution can be paused by the ❚❚ button, resumed by the button, and run step-by-step by the ►| button. The button refreshes the drawing.

If you do not see any graphs, try reloading several times.

Accepted terms

Only pure untyped lambda-terms are accepted, in the following grammar. You may need more parenthesis than you expect, especially for function application.

<var> := {variables}
<expr> ::= <var>  # variables
         | (\lambda <var>. <expr>)     # abstraction
         | (<expr> <expr>)             # application

Note that you will see the character λ as soon as you type \lambda.

What you can see

  • A graph, with the token indicated by the red edge.
    • Its Graphviz source is shown in the left gray box.
  • The token data below the graph, whose top lines are always the latest:
    • The left data is rewrite flag. The graph is rewritten whenever the flag is raised, i.e. set to <λ> or <!>.
    • The middle data is computation stack, used to determine the order of evaluating a function and its argument.
    • The right data is box stack, used to manage duplication of sub-graphs wrapped in a dashed box.

For more information




This tool uses graph-viz-d3-js for generating diagrams, and lo-js for parsing terms.

Clone this wiki locally
You can’t perform that action at this time.
You signed in with another tab or window. Reload to refresh your session. You signed out in another tab or window. Reload to refresh your session.
Press h to open a hovercard with more details.