Go Functions

External

• https://go.dev/ref/spec#Function_types

Internal

• Go Language

Overview

A function is a block of instructions, grouped together, and that optimally have a name. Functions exists for code reusability reasons: the function is declared once and then can be invoked any number of times. The functions can be reused from within the project, or from other projects, if the function is declared as part of a package that is imported in the project that needs to use the function.

Go functions allow variables to be declared, inside the function, with the short variable declaration.

Declaration

The function declaration starts with the func keyword.

func <function_name>([parameters]) [(return_declaration)] {
  // body
  [return [return_values]]
}

Parameters

Parameters are optional.

Invocation

All functions, except main() must be invoked explicitly from the program to execute.

A function is invoked, or called by specifying the function name, mandatory followed by open parentheses, optionally followed by arguments, if the function has parameters, then mandatory followed by closing parenthesis.

See:

Variables, Parameters, Arguments

main()

All programs in Go must have a main() function, where the program execution starts. The main() function must be declared in the main package.

You never call this function. When a program is executed, the main() gets called automatically.

Pass by Value vs. Pass by Reference vs. Pass by Pointer

Arrays are passed by value.

Built-in Functions

Built-in functions are available by default, without importing any package. Their names are predeclared function identifiers. They give access to Go's internal data structures. Their semantics depends on the arguments.

append()	cap()	close()	complex()	copy()
delete()	imag()	len()	make()	new()
panic()	print()	println()	real()	recover()

Length and Capacity

https://golang.org/ref/spec#Length_and_capacity

len()

len() returns string length, array length, slice length and map size.

cap()

cap() returns slice capacity.

Complex Number Manipulation

complex()

real()

imag()

TO DO: Continue to Distribute These Built-in Functions

close()

Allocation: new()

Making slices, maps and channels: make()

Appending to and copying slices: append(), copy()

Deletion of map elements delete()

Handling panics panic(), recover()

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Built-in functions for type conversions.

deplete this Go Concepts - Functions