This Monkey interpreter supports mathematical expressions, variable bindings, functions and the application of those functions, conditionals, return statements and even advanced concepts like higher-order functions and closures.
Supports the following data types: integers, booleans, strings, arrays and hashes.
Made following Writing An Interpreter in Go book
// Bind values to names with let-statements
let version = 1;
let name = "Monkey programming language";
let myArray = [1, 2, 3, 4, 5];
let coolBooleanLiteral = true;
// Use expressions to produce values
let awesomeValue = (10 / 2) * 5 + 30;
let arrayWithValues = [1 + 1, 2 * 2, 3];
Monkey also supports function literals and we can use them to bind a function to a name:
// Define a `fibonacci` function
let fibonacci = fn(x) {
if (x == 0) {
0 // Monkey supports implicit returning of values
} else {
if (x == 1) {
return 1; // ... and explicit return statements
} else {
fibonacci(x - 1) + fibonacci(x - 2); // Recursion! Yay!
}
}
};
Some of the data types:
/ Here is an array containing two hashes, that use strings as keys and integers
// and strings as values
let people = [{"name": "Anna", "age": 24}, {"name": "Bob", "age": 99}];
// Getting elements out of the data types is also supported.
// Here is how we can access array elements by using index expressions:
fibonacci(myArray[4]);
// => 5
// We can also access hash elements with index expressions:
let getName = fn(person) { person["name"]; };
// And here we access array elements and call a function with the element as
// argument:
getName(people[0]); // => "Anna"
getName(people[1]); // => "Bob"
Higher-order functions:
// Define the higher-order function `map`, that calls the given function `f`
// on each element in `arr` and returns an array of the produced values.
let map = fn(arr, f) {
let iter = fn(arr, accumulated) {
if (len(arr) == 0) {
accumulated
} else {
iter(rest(arr), push(accumulated, f(first(arr))));
}
};
iter(arr, []);
};
// Now let's take the `people` array and the `getName` function from above and
// use them with `map`.
map(people, getName); // => ["Anna", "Bob"]
Closures:
// Define the higher-order function `map`, that calls the given function `f`
// on each element in `arr` and returns an array of the produced values.
let map = fn(arr, f) {
let iter = fn(arr, accumulated) {
if (len(arr) == 0) {
accumulated
} else {
iter(rest(arr), push(accumulated, f(first(arr))));
}
};
iter(arr, []);
};
// Now let's take the `people` array and the `getName` function from above and
// use them with `map`.
map(people, getName); // => ["Anna", "Bob"]
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