call

call(x, args...)

If x is not a Function, then x(args...) is equivalent to call(x, args...). This means that function-like behavior can be added to any type by defining new call methods.

Examples

  1. Call a function with arguments:

    julia> function add_numbers(a, b)
              return a + b
          end
    julia> call(add_numbers, 5, 3)
    8

    In this example, the call function is used to invoke the add_numbers function with arguments 5 and 3. It returns the sum of the two numbers.

  2. Call a function-like object:

    julia> struct MultiplyByTwo
              value::Int
          end
    
    julia> (m::MultiplyByTwo)(x) = m.value * x
    
    julia> m = MultiplyByTwo(5)
    julia> call(m, 3)
    15

    Here, the call function is used to invoke the function-like behavior of the MultiplyByTwo object. The call method defined for MultiplyByTwo multiplies the object's value field with the argument x.

  3. Handle non-function objects:
    julia> x = 10
    julia> call(x, "Hello, world!")
    ERROR: MethodError: objects of type Int64 are not callable

    If the provided x is not a function or a function-like object, an error will be thrown. In this example, calling call with an integer x results in a MethodError because integers are not callable.

Common mistake example:

julia> call(5, 3)
ERROR: MethodError: objects of type Int64 are not callable

In this example, the mistake is passing an integer 5 as the first argument to call. Since integers are not callable, a MethodError is thrown. Make sure to pass a callable object or a function as the first argument to call.

See Also

User Contributed Notes

Add a Note

The format of note supported is markdown, use triple backtick to start and end a code block.

*Required Field
Details

Checking you are not a robot: