bosc v0.0.13

Bosc

A data-driven, object-oriented scripting language

Hello World

'Hello World!' print

'Hello World!'

Countdown

5 times #([x] 5 - x) push 'Boom'

{ '0': 5,
  '1': 4,
  '2': 3,
  '3': 2,
  '4': 1,
  '5': 'Boom' }

Pascals Triangle

local : choose #([n k]
  n ! / (k ! * ((n - k) !))) ,

local : pascals #([rows]
  rows times #([n]
    (n + 1) times #([k] n `choose` k))) ,

$(pascals 6) map #([x] x join ' ') join '\n' print

1
1 1
1 2 1
1 3 3 1
1 4 6 4 1
1 5 10 10 5 1

Objects (or Tables)

Everything is an Object

In Bosc there is only one data structure: the table. Everything is a table, including primitives like 3, 'Hello', and true. Hence forth I will use the terms object and table interchangeably.

The table is most similar to a map or dictionary in other languages. However, it also acts as an array by letting numerical keys represent list entries.

There are three ways to define a table: as a list [1 2 3], as a map {key 'value'}, and as a function #([args] symbol1 symbol2). In the end though, the different forms just choose how each value is assigned to a key.

Don't worry about the local : [variable] we will come back to that later.

local : list [1 2 3] ,
local : map  { name 'Gabe' age 23 } ,
local : fun  #([x] x + 1)

{ local: self,
 list: { '0': 1, '1': 2, '2': 3 },
 map: { name: 'Gabe', age: 23 },
 fun: { '0': 'x', '1': '+', '2': 1, args: { '0': 'x' } } }

The Interpreter

The interpreter is very simple and for the most part has one expectation about the structure of your code. Let me explain:

1. The first symbol consumed should be an object, for example 3.
2. The second symbol should be a method of the preceding object, for example +.
3. The next zero or more symbols should be the arguments for the previous method, for example 4.
4. Once the method is evaluated it takes the returned object and returns to state 2 (expecting another method).

Note that symbols are delimited by spaces.

Following the above process, lets explore the code block bellow:

3 + 4 / 2

3.5

In this example 3 is our object, + is our method, and 4 is the single argument (to the + method). This returns the object 7, which subsequently has the method / which takes the argument 2. The end result is the object 3.5.

Storing data with local

Like everything else in Bosc, local is a table. Every table comes preloaded with the : method. The : method takes two arguments, a key and a value, and creates that entry in the source object. It then returns the object manipulated. So, like in our earlier example, when we say local : x 3 we are assigning the value 3 to the x key of our local object.

local receives some special treatment from the interpreter. When the interpreter encounters an unknown symbol (variable name) it will check the local table for that key. If found it will inject the corresponding value in place of the symbol. Look at the example bellow. After we have defined x, we can use it as symbol in future statements.

local also has some special properties to enable lexical scoping -- we will explore this more when we learn how to define methods.

local : x 3 ,
x + 10

13

A quick note about ,

, is another preloaded method that comes with every object in Bosc. It takes one argument -- and then returns that argument. This allows one to switch the object they are currently operating on. In the example above, after the statement local : x 3, I no longer want to call any methods on local. Therefore, by using the , method I can switch gears and make x my source object.

Functions/Methods

A function is list of symbols with an args key that defines a list of arguments. The short hand to define a function is #([args] symbols).

The $( ... ) special form

The only exception to the object-method-argument rule is the special form $(function arg1 arg2). This allows one to call a function without having to reference local. That being said, there is never a strict requirement to do so. This is equivalent to local function arg1 arg2.

local : func #([x] x + 1) ,
$(func 5) ; Same result as "local fun 5"

6

To be continued . . .