#!/usr/bin/env golo
module demo.Tour

# A tour of what Turbo Golo colours, one construct per line or two. Every line
# here runs: `golo demos/syntax-tour/tour.golo` prints its way through. What the
# lexer reads but the interpreter's parser then refuses is in lexer-only.golo
# beside this file, which is coloured but does not run.

import gololang.Errors

----
A block comment runs from four dashes to the next four, over as many lines as
it likes, with --- near misses and "quotes" inside it left alone.
----

# Structs, unions and augmentations are capitalised by convention, and the
# convention is what the colour follows.
struct Point = { x, y }

union Shape = {
  Circle = { radius }
  Rect = { width, height }
}

augment Shape$Circle {
  function diameter = |this| -> this: radius() * 2
}

# A declared name is a function even though no parenthesis follows it.
function twice = |x| -> x * 2

function hidden = |x| {
  return x + 1
}

function main = |args| {
  # Numbers: integers, doubles, exponents.
  let count = 42
  let ratio = 3.14
  let small = 1.5e-3
  let big = 2E10

  # Strings, escapes, a multi-line string, and a hash that is not a comment.
  let greeting = "Hello, \"Golo\"\n"
  let hash = "# not a comment"
  let dashes = "---- not a comment ----"
  let multi = """
  a multi-line "string"
  with "quotes" left alone
  """

  # Builtins are the interpreter's own functions; DynamicObject is one too.
  println(greeting + hash + dashes)
  println(multi)
  println(str(count) + " " + str(ratio) + " " + str(small) + " " + str(big))
  let bag = DynamicObject()
  bag: name("Golo")
  println(bag: name())

  # Collections and comprehensions.
  let xs = list[1, 2, 3]
  let squares = list[x * x foreach x in range(1, 6) when x > 2]
  let pairs = map[["one", 1], ["two", 2]]
  println(xs + " " + squares + " " + pairs)

  # Control flow: if, while, for, foreach, match.
  var i = 0
  while i < 2 {
    i = i + 1
  }
  for (var j = 0, j < 2, j = j + 1) {
    println("for " + j)
  }
  foreach x in xs {
    println("foreach " + x)
  }
  let label = match {
    when count < 0 then "negative"
    when count == 0 then "zero"
    otherwise "positive"
  }
  println(label)
  if count > 40 and not (count is null) {
    println("big enough")
  } else {
    println("small")
  }

  # Structs, unions, augmentations, closures.
  let p = Point(1, 2)
  let c = Shape_Circle(2.0)
  println(p: x() + p: y())
  println(c: isCircle() + " " + c: diameter())
  let f = |a, b| -> a + b
  println(f(twice(20), hidden(1)))

  # Errors, and the Option union from gololang.Errors — Some is a variant,
  # not a builtin, so it takes the colour every capitalised name does.
  try {
    throw "boom"
  } catch (e) {
    println("caught: " + e)
  } finally {
    println("done")
  }
  let maybe = Some(1)
  println(maybe: isSome())

  # Names may be any Unicode letter, or an emoji.
  let été = "summer"
  let 😀 = "smile"
  println(été + " " + 😀)

  # Safe navigation on a null.
  let nothing = null
  println(nothing?: x())
}