PLang

PLang is a simple programming language that I made in course of a university course (MDDEV). It supports all the basic operations like conditionals, loops, and functions. It also supports variables, but they are not required. It is not meant to be used for anything serious, but it is a fun language to play around with.

Antlr4

PLang uses Antlr4 to parse the code. The grammar is in PLang.g4 file. The generated Antlr4 files are located in build/generated-src/antlr/main.

The ANTLR files will be generated automatically when executing any tests or building the project using gradle. To generate the files, without building the project use the gradle task generateGrammarSource.

Usage

PLang can be evaluated using the PLangEvaluator class which has an evaluate method that takes a String or an InputStream and an optional PLangContext as input.

PLangContext

The PLangContext is a class that holds the variables and functions. You can set variables using the addVariable method and get them using the getVariable method.
Functions can be set using the addFunction method and called using the callFunction method. At the moment only functions with no, one or two arguments are supported.

Example

val result = 0

val ctx = PLangContext()
ctx.addVariable("a", 1)
ctx.addVariable("b", 2)
ctx.addFunction("add", { arg1, arg2 -> result = arg1 + arg2 })

PLangEvaluator().evaluate("""
    add(a, b)
""", ctx)
println(result) // 3

Default Functions

At the moment there is only one default function out. It prints the given argument to the console.

Examples

You can see some examples in the test directory.

Syntax

Variables

Variables are declared with the def keyword. They can be assigned to with the = operator.

def x = "foo"
def y = 6 + 3
def z = y * 3
x = "bar"

Functions

Functions are declared with the def keyword. At the moment it's possible to define functions with zero, one or two parameters.

def function_1 (arg) {
    function_2(arg)
}
def function_2 (arg) {
    out(arg)
}
function_1("argument")

Conditionals

Conditionals are declared with the if keyword. They can be chained with the else if keyword. The else keyword can be used to catch all other cases.

if foo == "bar" {
    do_something()
} else if foo == "baz" {
    do_something_else_if()
} else if foo == "qux" {
    do_something_else_if()
} else {
    do_something_else()
}

Loops

Loops are declared with the loop keyword.

def i = 0

loop i < 10 {
    i = i + 1
}

Comments

Comments are started with // and end at the end of the line.