This tool presents how programs work. It focuses on presenting on the (call) stack, environments, and the heap. Such program must be written in SMoL, an educational language that support many language features commonly found in modern programming languages. SMoL has three surface syntaxes: Python-like, JavaScript-like, and Racket-like. Although programs must be written in the Racket-like syntax, this tool is able to present programs in two other, possibly more favorable syntaxes.
SMoL = Standard Model of Languages It includes (mutable) variables, mutable vectors (i.e., arrays), and first-class function.
See this document for more details.
All parameters are optional.
| (URL) Parameter | Type | Meaning |
|---|---|---|
program |
String | the program to run, written in the Lispy syntax |
syntax |
Lispy or JavaScript (or JS) or Python (or PY) |
the syntax in which to present everything |
nNext |
Non-negative Integer | simulate clicking the Next button nNext times |
randomSeed |
String | the seed used to generate heap addresses |
readOnlyMode |
Anything | when this parameter is set, stacker will present a much simpler UI that is just enough for reading the trace |
printOnRequest |
Anything | when this parameter is set, stacker will only print values as requested by (print v) (rather than printing all values returned to the top-level) |
To see examples of parameters, you can run programs in the stacker and then click the share buttons.
Programs that can be presented in Python-like syntax might or might not have a Python-equivalent semantics.
Programs that can be presented in JavaScript-like syntax might or might nor have a JavaScript-equivalent semantics.
Parsing errors are not reported with source code locations.
Keyboard shortcut is unstable.
ReScript-React registers tons of unused event handlers to the root element. This might raise accessibility problem.
Add list-processing higher-order functions.
letrec is interpreted as a block. It might be better to treat it as a primitive syntax.
let* is read as nested let. It might be better to treat it as a primitive syntax.
Some programs can't be presented in Python-syntax. This restriction is
mostly caused by the facts that Python have no let expressions, and
that Python's lambda only allow exactly one expression as its body.
Python uses the same syntax for variable definition and variable
mutation. Although this design might work well most of the time, there
are programs, especially tricky programs, where disambiguation is
needed. Python disambiguates with local and global keywords. We
made some effect to insert the keywords properly, but there is likely
a few corner-cases where the Python mode doesn't faithfully represent
Python or where a SMoL program can't be translated to Python. For
example, if a lambda mutates a free variable, we can't translate
that to Python.
npm install
This will install dependency packages.
npm run rescriptThis will start a ReScript program that keeps .res programs and
.js programs in sync.
npm run webpackThis will run a Webpack program that keeps .css, .js, etc. and the
final webpage in sync.
Xyz.res: a React componentxyz.res: a modulewebpack.config.js: the webpack configuration
https://developer.mozilla.org/en-US/docs/Web/Accessibility/ARIA
"No ARIA is better than bad ARIA."
https://inclusive-components.design/tooltips-toggletips/
Tooltips are a last resort, where space really is at a premium
This software application is developed by Kuang-Chen Lu (me) and Shriram Krishnamurthi.
The design is originally based on the systems designed by Shriram and John Clements. The original design can be found in the following publication:
Clements, John, and Shriram Krishnamurthi. "Towards a Notional Machine for Runtime Stacks and Scope: When Stacks Don’t Stack Up." Proceedings of the 2022 ACM Conference on International Computing Education Research-Volume 1. 2022.
During the revision of the design, many people have contributed feedback, notably:
- Students who attended CSCI1730 in 2022
- Kuang-Chen's friends and/or peers: Elijah Rivera, Siddhartha Prasad, Yanyan Ren, Yanru Liao
- Several audiences of the Stacker talk in the 12th RacketCon, notably