F♭
F♭ (pronounced F-flat) is a toy language.
F♭ is a dynamically typed array-oriented concatenative language like Forth, Joy, and others. F♭ is meant to be used interactively, for example in a CLI REPL, like R or the command shell, or in a stack based calculator. This constraint dictates many of the language features.
Features
Flat functional concatenative language
Stack based
RPN
Dynamic Types
Arbitrary-precision decimal and complex number type.
JSON format is a valid f-flat programs.
Why?
-
Designing a programming language in another language is a great way to learn about programming languages in general and the host language in particular.
-
Concatenative languages, with inherent functional composition, are a great way to explore functional programming and mathematics. Higher order functions (including math functions) are composed of smaller functions.
-
Because 0.1 + 0.2 = 0.3 and sqrt of -1 is not "not a number".
Example
Welcome to F♭ REPL Interpreter
F♭ Version 0.0.0 (C) 2000-2017 J. Harshbarger
f♭> 0.1 0.2 +
[ 0.3 ]
f♭> 0.3 =
[ true ]
f♭> clr
[]
f♭> -1 sqrt
[ 0+1i ]
f♭> 1 atan 4 *
[ 0+1i, 3.1415926535897932385 ]
f♭> * exp
[ -1-3.7356616720497115803e-20i ]
f♭> abs
[ 1 ]
f♭> clr
[]
f♭> "mersenne?" [ 2 swap ^ 1 - prime? ] ;
[]
f♭> 10 integers
[ [ 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 ] ]
f♭> [ mersenne? ] map
[ [ true, true, true, false, true, false, true, false, false, false ] ]
f♭> clr
[]
f♭> 1000 !
[ 4.0238726007709377384e+2567 ]
f♭> clr
[]
f♭> i !
[ 0.49801566811835599106-0.15494982830181068731i ]
f♭> { first: "Manfred" }
[ { first: 'Manfred' } ]
f♭> { last: 'von Thun' }
[ { first: 'Manfred' }, { last: 'von Thun' } ]
f♭> +
[ { first: 'Manfred', last: 'von Thun' } ]
f♭> clr
[ ]
f♭> [ 1 2 3 ]
[ [ 1 2 3 ] ]
f♭> dup
[ [ 1 2 3 ] [ 1 2 3 ] ]
f♭> [ 2 * ]
[ [ 1 2 3 ] [ 1 2 3 ] [ 2 * ] ]
f♭> map
[ [ 1 2 3 ] [ 2 4 6 ] ]
f♭> +
[ [ 1 2 3 2 4 6 ] ]
f♭> +
[ [ 1 2 3 2 4 6 ] ]
f♭> clr
[ ]
f♭> dbl-sqr-cat: [ dup [ 2 * ] map + ] ;
[ ]
f♭> [ 1 2 3 ]
[ [ 1 2 3 ] ]
f♭> dbl-sqr-cat
[ [ 1 2 3 2 4 6 ] ]
f♭> 'dbl-sqr-cat' see
[ '[ dup [ 2 * ] map + ]' ]
f♭> drop
[ ]
f♭> dbl-sqr-cat: expand
[ dup,2,*,*,Symbol((),swap,eval,dequote,+ ]
See other examples and guides here.
Project Goals
- conceptually simple
- interactive first
- minimal hidden state
- easy to type and read
- reads left to right, top to bottom
- whitespace not significant syntax
- no lambdas/parameters
- interactive development
- case insensitive
- flat concatenative language
- name code not values
- multiple return values
- concatenation is composition/pipeline style
- no unnecessary parentheses
- no surprises
- immutable data
- arbitrary-precision decimal and complex numbers
- percent values
- both double and single quotes
- returns error objects (TBD)
- pure functions
- host language interface (TBD)
- session saving (TBD)
- undo/redo
- state is serializable (TBD)
- modules, namespaces, and "closures"
Influences
- Many concatenative languages (HP RPL, Forth, Joy, Factor, XY)
- Haskell
- JavaScript
License
MIT