SML-NJ Parser & Style-checks

For UNC Comp 524

This repository contains supporting libraries and style-checks for SML programs for UNC Comp 524. They depend on SML/NJ, which helpfully exposes Compiler internals as structures which can be used, e.g., to parse a file and create an AST.

An example of parsing a file follows (sml style-utils/sources.cm):

(* make an AST *)
val parsed = FileParser.parse "...";
#ast parsed;

(* pretty print it *)
val depth = ...; (* 1, 2, …, 999, … *)
FileParser.pp depth parsed;

Creating style-checks for UNC Comp 524 is work-in-progress; an example of making a grader is in 524-f20-a3/a3grader.sml (see also 524-f20-a3.cm). The core idea is to write some checks with a return type result and a stringifier result_to_string, and pass that structure to GraderFn---this gives you a structure ascribing to GRADER, whose runall method takes a string representing a file-path and runs all of your checks. For example, A3Grader.runall on a passing implementation:

$ sml -m 524-f20-a3.cm
- A3Grader.runall "SocialDistance.sml";
no disallowed functions: pass
matching derived safe calls matching safe with matcher: pass
matching given safe calls matching safe with matcher: pass
curryable interpolated safe calls interpolated safe: pass
curried once interpolated safe calls curryable interpolated safe: pass
curried twice interpolated safe calls curried once interpolated safe: pass
curried matching given safe calls curryable matching safe with given safe matcher: pass
curried matching derived safe calls curryable matching safe with derived safe matcher: pass
no magic numbers in functions: pass
val it = () : unit

Utilities, such as an easy-to-use result type and stringifier and regexp-matcher for declarations, are in GraderUtils. Opening it is a quick way to get started building a grader.

Note that pass b is Pass if b is true, while fail b is Fail if b is true (and vice-versa for when b is false). This makes it easy to write checks like

(* fail when f is true *)
val does_not_f = fail o f
(* pass when g is true *)
val does_g = pass o g

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All SML/NJ systems contain compiled versions of the libraries we depend on.

To obtain a reference or source copy of the libraries that we depend on, the simplest route is to edit config/targets in your installation to include the line

request src-smlnj

Then run config/install.{sh,bat} with appropriate permissions. Extract compiler.tgz and system.tgz from the installation directory to obtain the full source.