A C version of a lexer for the Monkey programming language, originally written in Go, as presented in the book Writing An Interpreter In Go.
Copy pasting from the book:
Here is how we bind values to names in Monkey:
let age = 1;
let name = "Monkey";
let result = 10 * (20 / 2);
Besides integers, booleans and strings, the Monkey interpreter we’re going to build will also support arrays and hashes. Here’s what binding an array of integers to a name looks like:
let myArray = [1, 2, 3, 4, 5];
And here is a hash, where values are associated with keys:
let thorsten = {"name": "Thorsten", "age": 28};
Accessing the elements in arrays and hashes is done with index expressions:
myArray[0] // => 1
thorsten["name"] // => "Thorsten"
The let statements can also be used to bind functions to names. Here’s a small function that adds two numbers:
let add = fn(a, b) { return a + b; };
But Monkey not only supports return statements. Implicit return values are also possible, which means we can leave out the return if we want to:
let add = fn(a, b) { a + b; };
And calling a function is as easy as you’d expect:
add(1, 2);
A more complex function, such as a fibonacci function that returns the Nth Fibonacci number, might look like this:
let fibonacci = fn(x) {
if (x == 0) {
0
} else {
if (x == 1) {
1
} else {
fibonacci(x - 1) + fibonacci(x - 2);
}
}
};
Note the recursive calls to fibonacci itself! Monkey also supports a special type of functions, called higher order functions. These are functions that take other functions as arguments. Here is an example:
let twice = fn(f, x) { return f(f(x)); };
let addTwo = fn(x) { return x + 2; };
twice(addTwo, 2); // => 6
To build the REPL, clone the repository and run:
cd lexer-c
make
The executable will be generated in the bin
directory.
To run the tests:
make test