stacker

⚠️⚠️⚠️ This (DrRacket-based) stacker has been superseded by a new, web-based stacker ⚠️⚠️⚠️

https://github.com/LuKuangChen/stacker-2023

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Another implementation of smol. This implementation presents the execution with a stack-based model.

How to install, update, and uninstall

Please follow these instructions to install or update

1. Make sure you are in the DrRacket app.
2. Go to the menu File | Package Manager.... A window will pop up.
3. Make sure you are in the Do What I Mean tab of the pop-up window.
4. Set the Package Source field to Stacker (or https://github.com/LuKuangChen/stacker.git)
5. Click the Show Details button.
6. Set the Dependencies Mode field to Auto.
7. Click the Install button. (If you have already installed, you will see "Update" instead of "Install".) Most buttons will grey out immediately (except the Abort Install).
8. After the color of those buttons comes back, you can close the pop-up window. This usually takes less than 1 min.

Alternatively, you if the raco tool is availabe, you can install by running raco pkg install Stacker.

To uninstall

1. Make sure you are in the DrRacket app.
2. Go to the menu File | Package Manager.... A window will pop up.
3. Make sure you are in the Currently Installed tab of the pop-up window.
4. Set the Filter field to stacker.
5. Select the first result.
6. Click the Remove button. A confirmation window will pop up.
7. Click the Remove button in the confirmation window. Most buttons will grey out immediately (except the Abort Install).
8. After the color of those buttons comes back, you can close the pop-up window. This usually takes less than 1 min.

How to test whether an installation is successful?

First, make sure you are in the Racket language:

1. Make sure you are in the DrRacket app.
2. Go to the menu Language | Choose Language.... A window will pop up.
3. Select The Racket Language.
4. Click the OK button.

Run the following program in DrRacket

#lang stacker/smol/hof

(defvar x 2)
(defvar y 3)
(+ x y)

You should see a screenshot like this.

Usage

Usually, you will use the Stacker like other Racket #langs.

#lang stacker/smol/hof

(deffun (fact n)
  (if (zero? n)
      1
      (* (fact (- n 1)) n)))
(fact 3)

If you only want to see the (final) result, you can ask the stacker not to show the stack+heap configurations (note the second line). This way you don't need to click through the configurations and hence can see the result sooner.

#lang stacker/smol/hof
#:no-trace

(deffun (fact n)
  (if (zero? n)
      1
      (* (fact (- n 1)) n)))
(fact 3)

Language Levels

1. fun
2. state adds mutable variables and mutable vectors
3. hof adds first-class functions and let{,rec,*}

Grammar

Here is a glossary of smol grammar, where d stands for definitions, e stands for expressions, c stands for constants, and x and f are identifiers (variables).

d ::= (defvar x e)
    | (deffun (f x ...) body)
e ::= c
    | x
    | (lambda (x ...) body)
    | (λ (x ...) body)
    | (let ([x e] ...) body)
    | (letrec ([x e] ...) body)
    | (let* ([x e] ...) body)
    | (begin e ... e)
    | (set! x e)
    | (if e e e)
    | (cond [e e] ... [else e])
    | (cond [e e] ...)
    | (e e ...)

body    ::= d ... e ... e
program ::= d ... e ...