Syntax

Tao’s grammar is small and regular. Semicolons and parentheses are mostly optional; newlines are ordinary whitespace.

Comments

Line comments start with // and run to the end of the line.

// this is a comment
let x = 1

Structure of a program

A program is a sequence of top-level statements: const, fun, data, import, package, or an expression.

Inside a function body, the block holds let, assignment, return, leave, loop, or an expression.

package app

import a.b.c

const LIMIT = 100

data Point {
  x = 0
  y = 0
}

fun add(a, b) {
  return a + b
}

add(2, 3)

Semicolons

Semicolons after statements are optional. Both of these are valid and equivalent:

fun f(x) { let a = 1; a + 1 }; f(0)

fun f(x) {
  let a = 1
  a + 1
}
f(0)

Keywords

Tao has exactly seventeen keywords:

if     else  loop  leave  switch  package  import
const  data  fun   let    mut     try      return
and    or    not

Identifiers

Identifiers start with a letter or underscore, then any letters, digits, or underscores. Built-in names are capitalized (True, False, None).

Operators

Operators are grouped by precedence, from tightest to loosest. Higher rows bind tighter.

! and not are unary logical negation, binding as tightly as unary minus.

Flexible condition syntax

The parentheses around if and switch conditions are optional:

if x { 1 }

if (x) { 1 }