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YAMLScript-0.1.0
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/ YAMLScript

NAME

YAMLScript - Programming in YAML

SYNOPSIS

A YAMLScript program 99-bottles.ys:

#!/usr/bin/env yamlscript

main(number=99):
  map:
  - println
  - map(paragraph, range(number, 0, -1))

paragraph(num): |
  $(bottles, num) of beer on the wall,
  $(bottles, num) of beer.
  Take one down, pass it around.
  $(bottles, (num - 1)) of beer on the wall.

bottles(n):
  cond: [
    (n == 0), "No more bottles",
    (n == 1), "1 bottle",
    :else,    "$n bottles" ]

Run: yamlscript 99-bottles.ys 3

3 bottles of beer on the wall,
3 bottles of beer.
Take one down, pass it around.
2 bottles of beer on the wall.

2 bottles of beer on the wall,
2 bottles of beer.
Take one down, pass it around.
1 bottle of beer on the wall.

1 bottle of beer on the wall,
1 bottle of beer.
Take one down, pass it around.
No more bottles of beer on the wall.

Use the YAMLScript REPL:

$ yamlscript
Welcome to YAMLScript [perl]

user=> nums =: range(1 4)
user/nums
user=> nums
(1 2 3)
user=> map: [ println, nums ]
1
2
3
(nil nil nil)
user=> <ctrl-D>         # to exit
$

STATUS

This is very ALPHA software. Expect things to change.

DESCRIPTION

YAMLScript is a programming language that uses YAML as a base syntax. It feels like a YAML encoded Lisp, but with fewer parentheses.

In fact YAMLScript is a Lisp. It's a YAML-based specialized syntax reader for the Lingy programming language. Lingy is a port of the Clojure language to other languages (like Perl). Clojure is a Lisp hosted by the Java JVM.

INSTALLATION

YAMLScript is currently only available as a Perl CPAN module. You install it like so:

$ cpanm YAMLScript

Once installed you will have access to the yamlscript CLI command. You will also have library support to invoke YAMLScript directly from Perl.

YAMLSCRIPT LANGUAGE CAPABILITIES

  • Variable binding

    name =: 'world'

    Variable names use lowercase letters a-z, digits 0-9 and must start with a letter. Name parts may be separated by a dash -.

  • Variable dereferencing

    the-value =: name

    Unquoted words are treated as Lingy symbols.

  • Lingy Expressions

    Plain (unquoted) scalars are treated as Lingy syntax. Scalars starting with ( are Lingy expressions.

    answer =: (2 * 3 * 7)

    You can use a backslash to indicate turn YAML syntax into a Lingy syntax:

    my-vector =: \[1 2 3]

    Without the \ it would be read by YAML as [ "1 2 3" ].

  • String interpolation

    YAMLScript strings need to be quoted, since plain (unquoted) strings are seen as Lingy symbols (variables) or syntax.

    Lingy symbols or expressions preceded by a $ are interpolated into double quoted and literal style YAML scalars.

    # Double quoted strings are interpolated
- greeting =: "Hello, $name!"
# Multiline literal scalars are interpolated
- hi-bye =: |
  Hello, $name.
  Goodbye, $name.
# Single quoted strings are NOT interpolated
- string =: 'Hello, $name!'

  • Fixity:

    In Lingy (a Lisp) you say things like:

    (println (* 3 7))

    YAMLScript lets you say:

    println(3 * 7)

    That is function symbols can be placed before the opening paren. And prefix math operations can be made infix.

  • Function calls

    say:
  join: [' ', "Hello", "world!"]

    or

    say(join(' ' ["Hello" "world!"]))

  • Define functions

    square-and-add(x,y):
  ((x ^ 2) + y)

  • Define multiple arity functions

    sum:
  (): 0
  (x): x
  (x, y): (x + y)
  (x, y, z*): (x + (y + (sum z*)))

  • Conditionals

    if:
- (x > 50)            # condition
- say("$x wins :)")   # then
- say("$x loses :(")  # else

  • Try / Catch

    - try: (42 / 0)
  catch(e):
    say: "Caught error '$e'"

  • Iteration

    for (name):
- [Alice, Bob, Curly]
- say: Hello, $name!

  • Namespacing and Importing Modules

    ns My::Package:
  use:
  - Foo::Bar
  - Another::Module: [this, that]

    YAMLScript modules may be written in YAMLScript, Lingy or Perl.

AUTHORS

Copyright 2022-2023 by Ingy döt Net

This is free software, licensed under:

The MIT (X11) License