Liquid

Liquid is a scripting language.

Why

After reading an article about LLVM and how easy it is to create a DSL with it, I created this project (Sadly, I have no link the article itself). That was something I wanted to try. I started with some simple programming language constructs (and with no real concept of what the language should be). Additionally, I wanted to figure out how usable flex and bison are, since I didn't want to develop my own parser and lexer. All things which I had in my mind for a long time but never took the time to do. With LLVM it seams to be a feasible task. Just combining flex/bison with LLVM, voilà, that should be simple, right? However, while defining the syntax, more and more ideas of language elements that would be nice to have came up (thanks to @lucasb-eyer for the inspiring discussions). It resulted in a mix of some popular languages like python (at least the block formatting), ruby, some functional aspects and there may be others. Turns out that it took more time and effort than I thought. But it was still fun.

Installation

Prerequisite

• LLVM 6.0
• flex and bison.
• CMake 3.10

Build

1. Clone this repository.

git clone https://github.com/xkbeyer/liquid.git

2. Create a build directory

mkdir build

3. Change to the build directory and run cmake

cd build
ccmake ..

Make sure all Variables are set properly and then generate the build.

5. Run the make

make

or

make install

6. That's it.

Windows

After cmake was run the solution file is in the build directory. Start Visual Studio and you are ready to compile it.

Usage

liq script-file -h -d -v -q -ipath1;path2...;pathn

where

• h help: shows the usage.
• d debug: Disables the code optimizer.
• v verbose: print a lot of information.
• q quiet: don't show any output.
• i defines a list of additional path to look for files to import.

Liquid does parse the file, generates the code in memory and runs it.

Note Due to a bug at least one option must be set.

Example

./liq test.liq -q

Language Syntax

Literals

Can be any literal word including -_%$? and digits. It must start with a letter or an underscore.

a-b
otto4all
price?
_makeNew!

This can be used for symbols as variable names, function name etc.

Strings

A string is enclosed in " or '. A quote in a string must be escaped by a \.

"This is a string."
"This is
a multiple
line string."
'The man said:"This is a string." and left the place.'
"But \"here\" we need them."

Numbers

Simple Integer numbers, decimal numbers. Currently no binary and hex format is supported.

5
230
-88
27.5
0.345
.1
-1234.56
1.2e2
1.2e+2
1.2e-2

Boolean

A boolean can take the symbol true or false.

Array

An array is a container which can hold elements of arbitary types.

var array = [1,2,3,4]

The elements don't have to be of the same type.

var list = [1+2, 'Otto', true]

Hint: Currently only valid with a var declaration and an assigment.

Adding an element to the array above

list << 5

results in [3, 'Otto', true, 5]

Note This featue is currently under construction and not stable.

Comments

One Line

One line comment starts with #. All characters after that symbol are ignored until the end of line symbol.

Multiple Lines

A comment starts with @{ and ends with @}. All text in between is ignored.

Variable

Name

The same rules as for literals applies.

Declaration

Variables can be declared as integer, number or string.

int i
double d
string text
boolean b

And they can get an initial value:

int _abc = 1
int a = 1
int b = 2 
int a-b = a - b
boolean b = true
string text = 'This is a string.'

The var keyword is used to auto deduce the type of a variable.

var abc = 1  #deduce to int
var s = "Hello" #deduce to string.

Program

A program consists of several program blocks and each program block consists of statements. Each statement can be

• a control expression
• an assignment
• a function declaration
• a variable declaration
• a return statements

and so on.

Program Block

Program blocks are defined by the indention (similar to python).

block1
  block2
    block3
  block2
block1	

Control Expressions

if

if bool-expression 
  statements
else
  statements

while

while id > 0
  id = id - 1
  do-something
else
  display("upps nix\n")

return

return expression

Assignment

var a = 5

Function

Functions are defined as followed:

def aFunction( type param1, type param2 ) : return-type
  statements
  return expression

or if no return value is provided:

def aFunction( type param1, type param2 )
  statements

or if no parameter is needed:

def aFunction()
  statements

and any combination.

Calling a function

aFunction( 1, "text" )
aFunction()
int i = aFunction( 23 )

Class

def classname
    instance variable
    def method
        method-body

Hint: The keyword var can't be used to declare an instance variable.

Creating an object of a class

classname variable

The current class instance can be accesses via the keyword self. This is obligate if a class instance variable will be accessed.

Example:

def simple
    int myint = 5
    def get() : int
        return self.myint

simple p

int i = p.get()

Miscellaneous

Any class method can be declared outside a class declaration if the first argument is the class instance object.

def set(simple s, int val)
    s.myint = val

On the other side each method of a class can be called in two ways

simple p
int i = p.get()

or

int i = get(p)

Importing other script files can be done via the import keyword.

import some-other-file