Automated generation of pretty-printer in Rascal

Question

Can RascalMPL automatically generate pretty printer for a language? if not, what is the feasibility of this functionality within RascalMPL?

Answer 1

We have a number of ways to generate or construct pretty printers. Each with different ins and outs.

1. Write a recursive function with overloaded alternatives for every abstract or concrete syntax rule and use a string template on the right hand side. Use for-templates for lists, recursion for child nodes.

• String templates have auto-indentation for interpolated (recursive) variables.

2. The same, but map to the Box language for declarative two dimensional text layout.

• Box is a generalization of string templates that solves layout constraints in a similar way that CSS does paragraph layout and box layout. It can be found in the standard library.

3. Number 1. can be learned from a corpus of example syntax trees. The clair library (see packages on rascal-mpl.org) contains the code for this prototype.

• This works only on well-behaved ASTs, where the order of children is preserved correctly, for example.

4. Number 2 could also be learned but we should make a clone of 3. for that.
5. We are working on a codebuff clone but it has been a while we could find time for it. If you are interested to help out, please don't hesitate.