# 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 things, 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
- 2022-05-15 Clear progress being able to use simple while and if though thre are many glitches

ToDo List:

- [X] pow operator
- [X] binary operators
- [X] implement basic math functions
- [X] implement random_int(min, max)
- [X] implement print_number(message)
- [X] add unit tests
- [X] allow to set variables
- [X] read line comments
- [X] add modulus operator '%'
- [ ] add support for multiple characters operators
- [ ] add inclusive operators like '!=', '>=', '<='
- [ ] add support for priority operators
- [X] add input_number() std function
- [ ] add type() std function
- [X] add ceil() and floor() std functions
- [X] base of the CLI
- [ ] evaluate expression from stdin
- [X] read a file
- [X] if statements
- [X] while statements (with break and continue)
- [ ] repeat statement
- [ ] add functions support
- [ ] add config header file
- [ ] ability to modify keywords and customize the lang
- [ ] add static string support (just for ui)
- [ ] add print_string function
- [ ] add basic number list support
- [ ] add fully features strings support
- [ ] add [classic problem solving](https://rosettacode.org) with code examples
- [ ] add Web Assembly support and publish a demo website
- [ ] refactor: remove inconsistency on how functions returns error codes

## Installation

You will need to compile the code from source.

- Clone this repository
- Then compile (eg. with `make`)

I use GNU Make with GCC, but I'm sure you can use any C compilers though you may need to edit some part of the code to cope with other compilers (eg. binary constants).


## 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`).

One instruction set per line.

### Comments

Can only use single line comments with `#`

```
# this is a comment
```

### Data types

To begin with and order to simplify things we would only have numbers as datatypes.

When a variable is declared it can be 32 bit integer or 32 bit float.

The language may support strings literals in the future.

### Expression evaluation

function calls: func(arg_a, arg_b)
operators: +, *, /, ^, %, =, <, >, &, |, !

### Set a variable

```
set {VARNAME} to {EXPRESSION}
```

### Evaluate an expression without using the result

```
print_number(42)
```

### function definition

```
function {NAME} do
  ...
end
```

### Conditional structure

```
if {EXPRESSION} then
  ...
end
```

### Conditional loop

```
while {EXPRESSION} do
  ...
end
```

### Unconditional loop

```
repeat {INT EXPRESSION} do
  ...
end
```

```
repeat i from {INT EXPRESSION} to {INT EXPRESSION} do
  ...
end
```

### std functions

```
abs(nb)
sqrt,sin,cos,exp,ln,log etc.
print_number(nb)
input_number()
ceil(nb)
floor(nb)
random_int(min, max)
random_float(min, max)
type(var) -> return the type of a var as int
is_int(var)
is_float(var)
print_string(str)
print_newline()
print_ascii(nb)
```

# 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...