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...