Types and qualifiers

What can a variable hold, and when is its value known? Every value has a type, such as float or string, and a qualifier, which says whether it is fixed when the script is written, when its settings are read, on the first bar, or on every bar.

//@version=6
indicator("Types at work")
const int LEN = 20                              // const: fixed in the text
src = input.source(close, "Source")             // series: an input of the bar's prices
float avg = ta.sma(src, LEN)                    // a typed declaration
bool rising = avg > avg[1]                      // a bool is true or false, never na
plot(avg, "Average", rising ? color.green : color.red)

Types

Type	Holds	Its na
int	Whole numbers. Mixed with a float, it becomes one.	na
float	Numbers with a fraction.	na
bool	true or false.	None: where a condition reads a na, it reads false.
color	A colour and its transparency.	No colour.
string	Text.	The empty string, "".
label, line, box, table, linefill, polyline	A drawing on the chart. See Drawings.	No drawing.
chart.point	A point on the chart: a time, a bar index and a price. See chart.point.	No point.
array<T>, matrix<T>, map<K, V>	Collections of one type. See array, matrix and map.	No collection.
A type you declare	Fields you name. See type.	No object.
An enum you declare	One of the fields you list. See enum.	na

What na does to a calculation, how to test for it and why a bool can't be na are in What na is.

To change a value's type, call the type as a function: int(x) cuts the fraction toward zero, and float, bool, string and color convert as their entries say. box(na), line(na) and the other drawing casts give a typed na.

Qualifiers

A qualifier says when a value is known. They rank from the earliest to the latest:

Qualifier	Known	Examples
const	When the script is written.	Literals such as 20 or "Fast", and names declared const.
input	When the study's settings are read, before the first bar.	What an input.* call returns, but input.source.
simple	On the first bar, then fixed for the run.	syminfo.*, timeframe.*.
series	On each bar, and may change from bar to bar.	close, time, what ta.sma returns.

An expression takes the latest qualifier of its parts, so close * 2 is a series float. Some arguments need an earlier one: ta.ema's length must be a simple int, and an input.int's default a const int. Where the engine checks such an argument, it warns and runs the script anyway: see what a qualifier warning means.

Declaring a variable's type

Write the type before the name: float level = na, var int count = 0, array<float> closes = array.new<float>(). A declaration of na needs its type, since na alone has none: strict Pine refuses x = na. See Declaring.

A collection of collections, such as array<array<int>>, is AmenoScript only. TradingView needs a type with an array field in between. See AmenoScript's extensions.

Types are checked loosely here

This engine runs some scripts TradingView refuses: int n = 1.5 keeps 1.5, a reassignment can change a variable's type, and a number can stand as a condition, as in if close. Check a script on TradingView before relying on it there. The full list is in What runs here that TradingView refuses.