Types and methods

A type groups related values into one object. A method is a function you call on a value with a dot.

//@version=5
indicator("Swing tracker", overlay = true)

type Swing
    float price
    int bar
    bool isHigh = true

method distance(Swing this, float from) =>
    math.abs(this.price - from)

var last = Swing.new(high, bar_index)
if ta.pivothigh(high, 5, 5) == high[5]
    last := Swing.new(high[5], bar_index - 5)

plot(last.distance(close), "Distance to last swing high")

Types

type Name is followed by an indented list of fields: [type] name [= default]. Name.new(a, b) or Name.new(price = 1.0) makes an object. A field left out takes its default, else na ("" for a string, false for a bool).

p.price reads a field. p.price := 2 and p.count += 1 change it.

Objects are shared, not copied, when assigned: b = a is the same object. a.copy() (or Name.copy(a)) is a new one with the same fields. An object can hold other objects, arrays, maps and so on.

Methods

method name(Type this, ...) => is called as x.name(...). Two methods can share a name for different types, and a method can be defined on float, string and so on, as in close.double(). A built-in method of the same name (a.size() on an array) still works on its own types.

Types and methods are defined at the top level, before they are used.
Parameters can have defaults and be passed by name.
Reading a field of an na object stops the script with an error on that line.
p[1] is the object the variable held on the previous bar. On the first bar there is none, so guard it: bar_index > 0 ? p[1].x : na.