@include _ext.texi

@node Getting Started
@chapter Getting Started

Welcome to the O programming language! This chapter will introduce you to the
basics of the language's syntax. We'll cover variables, data types, operators,
control flow, and functions.

By the end of this chapter, you'll have a solid foundation in the O language
syntax and be ready to start writing your own programs. If you are already
familiar with C-like languages, you will find out that @code{O} behave pretty
much the same with some small quirks. Let's dive in!

@section An olang program

An O programming language program starts with a @code{main} function. This
function must return the program exit code.

@sethl olang
@verbatim
fn main(): u8 {
  return 0
}
@end verbatim

To compile the program you can use @code{olc}.

@sethl- bash
@verbatim
olc my_prog.ol -o my_prog
./my_prog
@end verbatim

@section Functions

Unlike C, O language does not require function prototypes. This means you can
call a function before it's defined, making your code more flexible and easier
to read in many cases.

@sethl olang
@verbatim
fn main(): u8 {
  return fib(8)
}

fn add(a: u32, b: u32): u32 {
  return a + b
}

fn fib(n: u32): u32 {
  if n <= 2 {
    return n
  }

  return add(fib(n - 1), fib(n - 2))
}
@end verbatim

@section Comments

Comments starts with a @code{#}.

@sethl- olang
@verbatim
# Hi I'm a comment and I'll be ignored by the compiler.
@end verbatim

@section Variables

@sethl- olang
@verbatim
var answer: u32 = 42
@end verbatim

@section Flow control

Any non zero expr is true.

@subsection If-Else

@sethl olang
@verbatim
if expr {
  # statement
} else if expr {
  # statement
} else {
  # statement
}
@end verbatim

While loop

@sethl olang
@verbatim
while expr {
  # statement
}
@end verbatim

@subsection While loop

@sethl olang
@verbatim
while expr {
  # statement
}
@end verbatim

@section Primitive data types

@table @samp

@item u8

Unsigned 8 bits.

@item u16

Unsigned 16 bits.

@item u32

Unsigned 32 bits.

@item u64

Unsigned 64 bits.

@end table

@section Binary Operations

@subsection Logical

@table @samp

@item Equals

@sethl- olang
@verbatim
expr1 == expr2
@end verbatim

Results zero (false) or one (true).

@item Less

@sethl- olang
@verbatim
expr1 < expr2
@end verbatim

Results zero (false) or one (true).

@item Less Equal

@sethl- olang
@verbatim
expr1 <= expr2
@end verbatim

Results zero (false) or one (true).

@item Greater

@sethl- olang
@verbatim
expr1 > expr2
@end verbatim

Results zero (false) or one (true).

@item Greater Equal

@sethl- olang
@verbatim
expr1 >= expr2
@end verbatim

Results zero (false) or one (true).

@item Or

@sethl- olang
@verbatim
expr1 || expr2
@end verbatim

Results zero (false) if both are true or one (true) if any is true.

@item And

@sethl- olang
@verbatim
expr1 && expr2
@end verbatim

Results zero (false) if any is false or one (true) if both are true.

@end table

@subsection Bitwise

@table @samp

@item Shift left

@sethl- olang
@verbatim
n << bits
@end verbatim

@item Shift left

@sethl- olang
@verbatim
n >> bits
@end verbatim

@item And

@sethl- olang
@verbatim
n & bits
@end verbatim

@item Or

@sethl- olang
@verbatim
n | bits
@end verbatim

@end table

@subsection Arithmetic

@table @samp

@item Addition

@sethl- olang
@verbatim
expr1 + expr2
@end verbatim

@item Subtraction

@sethl- olang
@verbatim
expr1 - expr2
@end verbatim

@item Multiplication

@sethl- olang
@verbatim
expr1 * expr2
@end verbatim

@item Division

@sethl- olang
@verbatim
expr1 / expr2
@end verbatim

@item Remaining

@sethl- olang
@verbatim
expr1 % expr2
@end verbatim

@end table

@section Pointers

Dealing with memory address.

@subsection Address of (&)

Get the address of a variable.

@sethl olang
@verbatim
var my_var: u32 = 0

var my_pointer: u32* = &my_var
@end verbatim

@subsection Dereferencing (*)

Accessing the value of the address a pointer points to.

@sethl olang
@verbatim
var my_var: u32 = 0

# The result of *my_pointer is the value of my_var (0).
*my_pointer

*my_pointer = 42
@end verbatim

The program above sets the @code{my_var}'s to 42.