TinyQL: A minimal but complete implementation of QL in Rascal

Total source lines of code (SLOC): 358.

Author: Tijs van der Storm, CWI.

For the original description of QL see the task description of the language workbench competition 2013

How to use:

• Install VS Code
• Install the Rascal extension from the Market place
• Clone this repository https://github.com/cwi-swat/tiny-ql
• Add the folder tiny-ql to your VS Code workspace (don't rename the folder).
• Open src/IDE.rsc and click on the link above the main function.

Now, the IDE for QL is enabled, and you can open the example questionnaires in examples.

Code overview:

• Syntax.rsc: grammar for QL
• Resolve.rsc: name resolution
• Check.rsc: type checking and cyclic dependency checking
• Compile.rsc: compilation to HTML and Javascript
• IDE.rsc: IDE wiring

IDE Features:

• Syntax highlighting
• Jump-to-definition
• Hover documentation
• Error marking
• Compile button
• Code folding
• Outline

Type checker features:

Errors

• reference to undefined question
• duplicate question declaration with different type
• conditional expression not of boolean type
• operands of invalid type to operator
• computed expression not conforming to declared type.
• cyclic data and control dependencies

Warnings

• empty prompt
• empty then/else-branch
• useless condition
• dead then-branch
• redeclared with different prompt

Notes

Division by zero is caught at run time (an alert will be shown), and 0 will be returned.

Mutual exclusion "bugs" (see mutual.myql for an example) are detected at run time and logged to the console.