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Functional Computer Programming Language

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Overview

fcpl is an expression-based, dynamic, weakly typed, functional programming language which transpliles into JavaScript. Its syntax is inspired by F# and CoffeeScript.

Examples

Hello World Program

// import print from the standard library
Import <| "std.print"
// log "Hello, World!" to the console
"Hello, World!" |> Print

Factorial Program

// import the standard library
Import <| "std"

Fun <| (Fact, (x), {
    If <| ((x, 1) |> GreaterOrEqualTo, {
        (
            x, 
            ((x, 1) |> Difference) |> Fact
        ) |> Product |> Return
    }, {
        1 |> Return
    }) |> Return
})

For <| (10, (x), {
    (x) |> Fact |> Print
})

Getting Started

You can run the fcpl command line by running:

node ./src/main.js

You can transpile an fcpl file by running:

node ./src/main.js FILE_PATH

This will output the transpiled JavaScript into ./output/output.js

Example:

node ./src/main.js ./examples/helloworld.fcpl && node ./output/output.js

Language Reference

fcpl source code consists of Variables, Literals and the Pipe Operator - No Exceptions.

The Pipe Operator

The Pipe Operator |> is a versitile operator which is used to control the flow of state through function calls.

// in other programming languages you might find the following:
Print("All your codebase are belong to us.")

// in fcpl you would write:
"All your codebase are belong to us." |> Print

fcpl also supports a left-facing Pipe Operator:

Print <| "All your codebase are belong to us."

Any Literal, Variable or Expression can be passed through the Pipe Operator

Literals

fcpl has 5 types of Literal values: String, Number, Collection, Pure Scope and Impure Scope.

Strings are wrapped in double quotes and behave identically to JavaScript Strings.

"Hello, World!" |> Print
"Hello \n World!" |> Print

Numbers:

10 |> Print
10.83 |> Print

Collections are wrapped in () brackets and are used to group data.

(3,1,4,1,5,9) |> Print // Prints: [3, 1, 4, 1, 5, 9]
// they can contain different types of literals
("This is a string",1,4,1,"This too",9) |> Print
// they can contain other collections too
(("this is a nested collection", 99),1) |> Print

Pure Scopes contain immutable state and pure expressions and is wrapped in {} brackets.

{
    "Printing from a pure scope." |> Print
}

You are not allowed to use impure state inside of a pure scope:

// assign the Literal 10 to the Id 'impureValue' as a Variable
(impureValue, 10) |> ImpureAssign
{
    impureValue |> Print // creates a compile time error: you are not allowed to use impure state inside of a pure scope.
}

You also cant create impure state inside of a pure scope:

{
    (impureValue, 10) |> ImpureAssign // creates a compile time error: you cant use ImpureAssign inside of a Pure Scope
}

Impure Scopes contain mutable and immutable state and impure or pure expressions. They are wrapped with [] brackets.

[
    // declaring mutable, impure state
    (impureValue, 10) |> ImpureAssign
    impureValue |> Print
]

Variables

Variables are a container for a Literal value. You can declare a variable through the ImpureAssign, PureAssign, or Fun built-in functions.

// set 'variableName' to "variable value" as an impure, mutable variable
(variableName, "variable value") |> ImpureAssign
// set 'x' to 10 as a pure, immutable variable
(x, 10) |> PureAssign

Functions are also assigned to a variable.

// set 'FunctionName' to a pure function which takes two arguments and returns 0
Fun <| (FunctionName, (functionParameter1, functionParameter2), {
    functionParameter1 |> Print
    functionParameter2 |> Print
    0 |> Return
})

// set 'ImpureFunctionName' to an impure function which takes two arguments and returns 0
// notice the `[]` brackets
Fun <| (ImpureFunctionName, (functionParameter1, functionParameter2), [
    functionParameter1 |> Print
    functionParameter2 |> Print
    0 |> Return
])

Dmrgn/fcpl