langatator/README.md

Langatator

A very basic interpreted programming language.

Background

The goal of this project is to create a simple implementation of a BASIC-like language just to learn a few things along the way and practice my C programming skills.

No need to do complex thing, just to create a simple interpreted language that can be used to do some arithmetics and create for example a number guessing game.

I didn't really study how others languages works beforehand, I'm just guessing how I'm implementing things so that I can make mistakes to learn from.

Progress

• 2022-04-29 : Implementation of a basic evaluator engine to evaluate arithmetic expressions and call functions

ToDo List:

• pow operator
• binary operators
• implement basic math functions
• implement random_int(min, max)
• implement print_number(message)
• implement input_number()
• base of the CLI
• evaluate expression from stdin
• read a file
• allow to set variables
• read line comments
• conditionals
• add unit tests
• function call stack

The language

You would be able to use the lang directly via CLI, via a REPL or by writing in a file (file ext .ltor).

To begin with and order to simplify things we would only have numbers as datatypes (so an abstraction with int or float under the hood).

One instruction set per line.

Comments

Can only use single line comments with #

# this is a comment

Expression evaluation

can only operate on integer

function calls: func(arg_a, arg_b) operators: +, *, /, ^

Set a variable

set {VARNAME} to {EXPRESSION}

Eval an expression without using the result

eval print_number(42)

function definition

function {NAME}
begin
...
end

Conditional structure

if {EXPRESSION} then
begin
    ...
end

Conditional loop

while {EXPRESSION} do
begin
    ...
end

Unconditional loop

repeat {EXPRESSION THAT EVALUATE TO INT}
begin

end

std functions

abs(nb)
sqrt,sin,cos,exp,ln,log etc.
print_number(data)
input_number()
random_int(min, max)

Evaluator (draft)

EDIT: that's not actually quite how I implemented the evaluator.

Map

componentList: bytes steam first byte is a uint8 representing the type of the component then depending on the type of the component there is 0 or N bytes

components types:

• name: integer size: 4 bytes (for int)
• name: open parenthesis size: 0 bytes
• name: close parenthesis size: 0 bytes
• name: float size: 32 bytes (IEEE 754)
• name: operator size: 1 byte (255 operators are possible)
• name: function designator desc: id of a function size: 2 bytes (65536 functions are possibles)

Example map of 9+(5*(8+6))

lexed stream -TYPE:NUMERAL VALUE:9 -TYPE:OPERATOR VALUE:PLUS -TYPE:OPEN_PARENTHESIS VALUE:NULL -TYPE:NUMERAL VALUE:5 -TYPE:OPERATOR VALUE:TIMES -TYPE:OPEN_PARENTHESIS VALUE:NULL -TYPE:NUMERAL VALUE:8 -TYPE:OPERATOR VALUE:PLUS -TYPE:NUMERAL VALUE:6 -TYPE:CLOSE_P VALUE:NULL -TYPE:CLOSE_P VALUE:NULL

scan the whole lexed stream

So there will be a kind of time line with reference, a list of reference

in the begining we allocate two lists, one for the component type, one for the component values

Dynamics lists

we allocate N bytes (uint_8 list[2048])

methods:

list_length() list_assign_int(int index, int value) list_assign_float(int index, float value) list_assign_uint_8(int index, uint_8 value) list_get_int(int index)

etc...