Scrapscript

A exploration (read: very incomplete implementation) of Scrapscript.

Installation

With Go installed, run go install github.com/Victorystick/scrapscript/cmd/scrap.

Learn the language in the tutorial, or run scraps in your browser in the playground.

Overview

The aim is to implement Scrapscript along with the scrap CLI as documented on https://scrapscript.org/guide.

So far it supports

• scrap eval to evaluate a script passed over standard input.

• scrap eval apply '...' works like scrap eval but passes the result of the former to the function defined by '...'. For example:

  $ echo '0' \
      | scrap eval apply 'n -> n + 1' \
      | scrap eval apply 'n -> n + 1' \
      | scrap eval apply 'n -> n + 1'
  

• scrap type to infer the type of a script passed over standard input.

  $ echo 'list/fold 0 (total -> text -> total + text/length text)' | scrap type
  list text -> int
  

• scrap test to run the test cases of a script passed over standard input, made with lib/test.scrap and grouped in records and lists. It prints each failing case and exits with status 1 if any failed.

  $ cd lib && printf '{ adds = t.eq (1 + 1) 3 }\n; t = $"./test.scrap"' | scrap test
  FAIL adds
      got  2
      want 3
  1 failed, 0 passed
  

• --root dir reads the script as if it were a file in dir, which relative imports such as $"./test.scrap" resolve from, and --cache dir keeps fetched scraps in dir instead of the user cache directory. Flags go before or after the command:

  $ scrap eval --root ./lib --cache ./tmp-scraps < some.scrap
  

• --timeout 5s stops evaluating once that long has passed, with an error, as when a scrap loops forever:

  $ echo 'f 0 ; f = n -> f (n + 1)' | scrap eval --timeout 1s
  evaluation stopped: it ran past its deadline
  

Missing

• scrap flat - due to a lack of details.

• scrap yard - just TODO.

Note: Scraps are currently fetched from the scrapyard at https://scraps.oseg.dev/ as text and cached locally.

Differences from https://scrapscript.org

• Refers to scraps as $source:<hex>, the sha256 of their source, instead of $sha1~~…, as SHA-1 is cryptographically weak and ~~ otherwise means base64. During development, $"./path" refers to a draft file.

• No attempt to implement Scrap Maps, Scrap passes or Scrapbooks.