It is practically impossible to teach good programming to students that have had a prior exposure to Hatter: as potential programmers they are mentally mutilated beyond hope of regeneration.
-– Edsger W. Dijkstra (allegedly)
Hatter is a small, whitespace sensitive templating language with HTML support built right in. Its HTML features and syntax are a cheap knock off of Imba, except Hatter produces raw, static HTML - no JavaScript in sight.
Hatter can be used to generate static web sites or to render server side content in a good ol' fashioned web application - either with Vial or your Rust web framework of choice.
If you're feeling adventerous, or mad as a hatter, you can use the standalone binary to turn templates into HTML files, or include the zero-dependency Rust library in your (web/cli/?) application.
Here are a few basic examples of what Hatter looks like and the HTML it generates:
<!-- Hatter -->
<#main> Hi there!
<!-- Generated HTML -->
<div id='main'>Hi there!</div><span.big.bold> Welcome!
<span class='big bold'>Welcome!</span><.links> for link in nav-links
<a href={link.href}> link.text
<div class='links'>
<a href='/link1'>First Link</a>
<a href='/link2'>2nd Link</a>
<a href='/link3'>Final Link</a>
</div><form GET="/search">
<input@query:text placeholder="Search..." /> <input:submit />
<form method='GET' action='/search'>
<input name='query' type='text' placeholder='Search...' />
<input type='submit' />
</form>- Auto-closing HTML tags and code blocks based on indentation:
<h1> Welcome, <i> Robbecomes<h1> Welcome, <i> Rob </i></h1>
- Shorthand for
id,class,type, andnameattributes:<div#id><div.class1.class2><input@form-field-name><input:text>
- Dynamic values for regular attributes:
<div page-num={page.id}>
- Conditionally set attributes or enable shorthand:
<div .logged-in=logged-in?><div data-map=is-map?>
- String interpolation:
<span.greeting> "Hey there {name}. 2 + 2 is {2 + 2}"
- Shorthand interpolation:
<span #page-{page.id} .is-{page.type}> page.title
- Implicit divs:
<#main>becomes<div id='main'>
- Implicit closing tags:
<i>delicious</>becomes<i>delicious</i>
- Easy inline JavaScript:
<li> <a onclick=(alert("Oink!"))> "🐷"
- Basic types:
bool, int, float, string, list, map, fn
- Loop over
listandmap:<ul> for page in pages do <li id=page-{page.id}> page.namefor k, v in some-map do <td> k </> <td> v
- if/else statements
if logged_in? then <h2> Welcome back!
- Error-checked assignment with
:=and=:name := 'Bob'will error if name is already set.name = 'Bob'will error if name isn't already set.
- Call functions defined in Rust:
<div.name> to-uppercase(name)
- Define your own Hatter functions with strict arity and implicit
return values:
def greet(name) do print("Hey there, {name}!")greet("Lydia")printsHey there, Lydia!
- Define your own Hatter operators:
def ++(a, b) do concat(to-uppercase(a), ' ', to-uppercase(b))"one" ++ "two"returnsONE TWO
- Closures and function literals:
adder := fn(x) fn(y) x + ythenadd1 := adder(1)add1(200)returns201
- Call functions with keyword arguments:
def greet(title, name) do print("Hiya, {title}. {name}!")greet(name: "Marley", title: "Dr")printsHiya, Dr. Marley!
dokeyword for one-line blocks:if 2 > 1 do print("Obviously")for x in list do print(x)
thenkeyword for one-lineifstatements:if 2 > 1 then print("Yup!") else if 2 < 1 then print("Impossible.")
- Hatter will add a
<!DOCTYPE>and wrap everything in<html>if the first tag in your template is<head>.
There are two ways to use Hatter:
Hatter can (primarily) be used as a templating language from within your Rust applications.
Simply add Hatter to Cargo.toml:
[dependencies]
hatter = "0.1"Then create a hatter::Env, which represents the top-level Hatter
scope for your template, to set variables and render your template:
use hatter::{Args, Env, Value};
let mut env = Env::new();
env.set("name", "Bobby Boucher");
env.set("age", 31);
env.render(r#"
<p> <b>Name:</> name
<p> <b>Age:</> age
"#)You can also write functions in Rust and make them available to your HTML templates:
use hatter::prelude::*;
fn quote(args: Args) -> Result<Value> {
let file = std::fs::read_to_string("quotes.txt")?;
let list_of_quotes: Vec<_> = file.split('\n').collect();
let line = match args.need_number(0)? as usize {
n if n > list_of_quotes.len() => 0,
n => n,
};
Value::from(list_of_quotes[line]).ok()
}
fn main() {
let mut env = Env::new();
env.set("quote", quote);
println!("{}", env.render("<div> quote(1)").unwrap());
}For more infomation see the API Documentation.
Hatter can be used as a regular command line program to turn .hat
files into HTML.
Just install it using cargo:
cargo install hatterThen point it at any .hat file:
$ cat test.hat
<b.test> "Testing 1 2 3 {2 + 2}"
$ hatter test.hat
<b class='test'>Testing 1 2 3 4 </b>You can also install Hatter with a readline-powered REPL:
cargo install hatter --features replTo launch it, start hatter with no arguments:
$ hatter
Hatter v0.0.1 REPL
>> 1 + 2
3- HTMLized error page
- show error location in source text on runtime errors
- Define your own tags:
def <item(item)> do <li.item data-id={item.id}> item.text.
- Optional type checking for functions
- stdlib
- VSCode Extension
- luacheck-style tool
- LSPc
Hatter is licensed under either of the following, at your pleasure:
- Apache License, Version 2.0, (LICENSE-APACHE or http://www.apache.org/licenses/LICENSE-2.0)
- MIT License (LICENSE-MIT or http://opensource.org/licenses/MIT)
Imba is licensed under the MIT License.