laughing-spork

Programing language inspired by Lisp and YAML.

Live demo

https://vitalyvb.github.io/eval/

Converted from Python to JavaScript. Python code had to be changed for the (mostly) successfull conversion.

Some features are not supported by the live versions, for example there's a parse error for YAML lists constructed with [ and ].

Check the browser console for some (error) messages.

Examples

Define a function val. The function computes expression 2 * 2 and returns the value. Call the function.

---
- - define
  - val
  - - '*'
    - 2
    - 2
- val

Result: [<Num: 4>]

---

Flip-flop example with lambda and a closure

---
- - define
  - flip-flop
  - - - lambda
      - - state
      - - lambda
        - []
        - - define
          - state
          - - '*'
            - state
            - -1
        - state
    - 1

- - flip-flop
- - flip-flop
- - flip-flop

Result: [<Num: -1>, <Num: 1>, <Num: -1>]

---

Lambda functions and function composition.

---
- - define
  - inverse
  - - lambda
    - - x
    - - begin
      - - '*'
        - x
        - -1
- - define
  - add2
  - - lambda
    - - x
    - - begin
      - - '+'
        - x
        - 2
- - define
  - compose
  - - lambda
    - - f
      - g
    - - lambda
      - - x
      - - f
        - - g
          - x
- - define
  - comp
  - - compose
    - inverse
    - add2
- - comp
  - 10

Result: [<Num: -12>]

---

A generator using call-with-current-continuation

---
- - define
  - iter
  - - lambda
    - - from
      - to
      - f
    - - if
      - - eq?
        - from
        - to
      - - f
        - from
      - - begin
        - - f
          - from
        - - iter
          - - '+'
            - from
            - 1
          - to
          - f

- - define
  - make-gen
  - - lambda
    - - from
      - to
    - - define
      - control-state

      - - lambda
        - - return
        - - iter
          - from
          - to

          - - lambda
            - - element
            - - define
              - return
              - - begin
                - - call/cc

                  - - lambda
                    - - resume-here
                    - - define
                      - control-state
                      - resume-here
                    - - return
                      - element

        - - return
          - "end"

    - - define
      - generator
      - - lambda
        - []
        - - call/cc
          - control-state

    - generator


- - define
  - gen
  - - make-gen
    - 0
    - 2

- - gen
- - gen
- - gen
- - gen

Result: [<Num: 0>, <Num: 1>, <Num: 2>, <Str: 'end'>]

---

Alternative syntax (not supported by the live demo version)

---
- - define
  - fac'
  - - lambda
    - [ x, acc ]
    - [ if, [ 'eq?', x, 1 ], acc, [ fac', ['-',  x, 1 ], [ '*', acc, x ] ]]

- - define
  - fac
  - - lambda
    - [ x ]
    - [ fac', x, 1 ]

- [ fac, 20 ]

Result: [<Num: 2432902008176640000>]

Built-in functions

Arithmetic and comparison

• +
• *
• -
• /
• eq?

List functions

• list
• first
• rest
• cons
• list?
• length
• empty?
• elem

Standard functions

• debug
• display
• sleep

Special functions:

• &apply
• &apply?
• &apply.exp
• &apply.args
• &apply.tolist
• &list.elist
• &list.eval
• &lambda
• &format
• &if

Very special functions:

• &rest
• begin
• call
• call/cc
• eval
• quote
• define
• defmacro
• callmacro

Prelude macros

• lambda
• if
• defun
• cond

Bugs

Yes.

The name

The name was proposed by GitHub project name generator.

Seems appropriate.