TinyLang

TinyLang is a template language build as a simple tree-walk interpreter using PEST.

One of the design decisions is that you cannot assign new values to variables inside the template file. So you cannot write something like {% a = 2 %}, you have to actually setup the state on the Rust side. One small exception is the for loop which does assign and create a new variable to be used inside the template.

State

Feature	State	Syntax
HTML	✅	any char
Variables	✅	lowercase alphanumeric e.g. (myvar)
Logical operators	✅	and, or
Print Statements {{}}	✅	{{ 1 + 2 + 3 }}
Bool, String, Numeric types	✅	true, false, 'a string', 3
if/else	✅	{% if true %} {% else %} {% end %}
loops	✅	{%for item in array %} {% end %}
function calls	✅	my_function('abc')
Dot operator	✅	something.something_else

Missing

• Documentation

Examples

Anything not inside {{ }} (print statement) and {% %} (dynamic statement) will be in the output.

The language supports:

Numbers (integers and floats), String (e.g. 'a string'), bool (true and false).

It's possible to use Vectors (Vec<TinyLangType>) and Objects (a variable with a HashMap<String, TinyLangType>), but it's not possible to construct them inside a template file. It's only possible to create those types on the Rust side. You can check the examples on how to use the language at tests/examples.rs .

Using as a library

You can call the eval method which receives the template (&str) and the State (variables and functions accessible inside the template). It returns the parsed string or an error.

You can also try it out at: https://tinylang.elias.tools

Posts

• https://www.elias.sh/posts/peg_and_rust.html

Acknowledges

Thank you @Karreiro for the pair-programming on Twitch.