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syntax.md

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Syntax

Comments

Line comments start with # and end at the end of the line.

# This is a comment

Keywords

This is a list of all the keywords in Tx.

and as async await break continue else false for fn if import impl in
inout is let loop nil match out or return self struct super trait
true var while Any Array Bool Char Float Int Map Nil Self Str Tuple

Identifiers

Identifiers must start with a letter or underscore and may contain letters, digits and underscores. Identifiers are case sensitives.

simple
snake_case
camelCase
CamelCase
ALL_CAPS
_under_score
abc123

Newlines

Newlines are considered as white space and have no significance

Statements

A Tx program consist of a series of statements. Tx have different kind of statements, like:

  • Declaration statements

  • Control flow statements

  • Expression statements, which are expressions followed by a semicolon ;.

    # function declaration
fn main() Nil {
    # variable declaration
    let x = 5;

    # expression statements
    x;
    x + 1;
    15;
}

Expressions

Expressions produces a value, and are parsed using operator precedence.

PREC OPERATORS DESCRIPTION
1 . () [] {} Function call, Grouping, Subscript, Block scope
2 ! - Not, Negate
3 * / Multiply, Divide
4 + - Add, Substract
5 < > <= >= Less-than, Greater-than
6 == != Equal, Not equal
7 and Logical AND
8 or Logical OR
9 = Assignment

Blocks

Curly braces are used to define blocks. Blocks are expressions and produce a value. The last expression in the block is used as the block result expression. Unless the last expression is followed by a ; (which discard the expression result by making it a statement) in which case the result value is nil.

let x = 5;

let y = {
    let x_squared = x * x;
    let x_cube = x_squared * x;

    # This expression will be assigned to 'y'
    x_cube + x_squared + x
};

let z = {
    # The semicolon suppresses this expression and `nil` is assigned to `z`
    2 * x;
};

In places where a statement is expected, a block can be used without being followed by a ;

let x = 0;

x+1;                # here a ';' is needed to make expr into statement

{ let y = 666; }    # no ';' needed after '}'

{
    let a = 5;
}                   # no ';' needed here neither

Blocks are mandatory for the bodies of functions and control flow statements. The result value of the block is discarted when used as the body for a while or for loop statement.

if (true) { print("hello"); }

if (true) print("hello");      # Invalid syntax