Declaring functions

Pine has an extensive library of built-in functions which can be used to create scripts. Users can also create their own functions.

Single-line functions

Simple functions can often be written on one line. This is the syntax of single-line functions:

<identifier>(<list of arguments>) => <expression>

Here is an example:

f(x, y) => x + y

After the function f has been declared, it’s possible to call it using different types of arguments:

a = f(open, close)
b = f(2, 2)
c = f(open, 2)

The type of the value returned by function f is determined automatically and depends on the type of the arguments used in each particular function call. In the example above, the type of variable a is series because the arguments are both series. The type of variable b is integer because arguments are both literal integers. The type of variable c is series because the addition of a series and literal integer produces a series result.

Pine Scipt functions do not support recursion. It is not allowed for a function to call itself from within its own code.

Multi-line functions

Pine also supports multi-line functions with the following syntax:

<identifier>(<list of arguments>) =>
    <variable declaration>
    <variable declaration or expression>

The body of a multi-line function consists of several statements. Each statement is placed on a separate line and must be preceded by 1 indentation (4 spaces or 1 tab). The indentation before the statement indicates that it is a part of the body of the function and not part of the script’s global scope. After the function’s code, the first statement without an indent indicates the body of the function has ended.

Either an expression or a declared variable should be the last statement of the function’s body. The result of this expression (or variable) will be the result of the function’s call. For example:

geom_average(x, y) =>
    a = x*x
    b = y*y
    sqrt(a + b)

The function geom_average has two arguments and creates two variables in the body: a and b. The last statement calls the function sqrt (an extraction of the square root). The geom_average call will return the value of the last expression: (sqrt(a + b)).

Scopes in the script

Variables declared outside the body of a function or of other local blocks belong to the global scope. User-declared and buit-in functions, as well as built-in variables also belong to the global scope.

Each function has its own local scope. All the variables declared within the function, as well as the function’s arguments, belong to the scope of that function, meaning that it is impossible to reference them from outside — e.g., from the global scope or the local scope of another function.

On the other hand, since it is possible to refer to any variable or function declared in the global scope from the scope of a function (except for self-referencing recursive calls), one can say that the local scope is embedded into the global scope.

In Pine, nested functions are not allowed, i.e., one cannot declare a function inside another one. All user functions are declared in the global scope. Local scopes cannot intersect with each other.

Functions that return multiple results

In most cases a function returns only one result, but it is possible to return a list of results (a tuple-like result):

fun(x, y) =>
    a = x+y
    b = x-y
    [a, b]

Special syntax is required for calling such functions:

[res0, res1] = fun(open, close)
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