`oris`

An interpreter for the Monkey programming language

Examples

```

line comment starts with `#`

integer

let positive = 42; # use let <identifier> = <expression> to declare variable let negative = -3; let zero = 7 + -7;

boolean

let yes = !false; let no = true == false;

string

let description = "Oris is an interpreter for the monkey programming language";

sequence

let seq = [true, 2, 3, 5, 6 + 1, "hello, world"];

map

key can be integer, boolean or string

let pairs = { 1: true, false: 4, "key": "value" };

function

let double = fn(x) { x * 2 # last expression's value becomes function's return value };

assert_eq(double(3), 6);

`assert_eq` is a builtin function that stops interpreting

if the two arguments are not equal to each other

closure (function can also capture values from environment)

let map = fn(seq, mapper) { let iter = fn(from, to) { if len(from) == 0 { # () around condition is optional return to; }

    iter(                   # call iter recursively
        tail(from),         # built-in `tail` returns elements after the first one
        append(             # built-in `append` add one element to tail and return the new sequence
            to,
            mapper(         # call the captured `mapper` function
                head(from)  # built-in `head` returns the first element
            )
        )
    )
}

iter(seq, [])               # `to` starts with an empty sequence

};

assert_eq(map([1, 2, 3], double), [2, 4, 6]);

calculate fibnacci number

1, 1, 2, 3, 5, 8, 13, 21

let fib = fn(x) { if x < 2 {
return 1; }

fib(x - 1) + fib(x - 2)

};

print(fib(7)); # use built-in function print to write the result 21 to stdout ```

oris