Go Concepts - Operators

External

• Go Specification - Operators: https://golang.org/ref/spec#Operators

Internal

• Lexical Structure

+

Addition or concatenation. The compiler figures out the semantics based on the operands' types.

Applies to:

• strings

-

Subtraction

*

* is the multiplication operator.

As "address operator", * is used with pointers as dereference operator. For more details see reference and dereference operators.

* designates pointer types.

&

& is the reference operator. For more details see reference and dereference operators.

/

Division

%

Remainder

=

The assignment operator.

+=

Addition and assignment.

==

The equality operator. Returns a boolean value.

Can be used to test string equality.

[]

"[]" is the indexing operator. If the index is out of bounds, the runtime generates a run-time panic:

panic: runtime error: index out of range

Applies to:

• strings
• arrays
• slices
• maps

:=

Short variable declaration operator. It does variable declaration and assignment (initialization). The type of the variable is inferred from the right side expression.

<-

<- is the left arrow operator. It is used to send and receive messages on channels.

.

. is used for field access and method calls:

Field Access

Used to access of a struct's fields.

When used for field access, . can be used both with a struct value or a pointer to that struct value. In both situations it has the same semantics.

Also see fields

Method Call

Used to invoke a method on the instance of the type the method is associated with, or on the pointer to an instance of the type the method is associated with.

When designating a method call, . can be used both with a value or a pointer. In both situations it has the same semantics. If ptr is a pointer, then ptr.m() is a shorthand for (&ptr).m(),

Also see methods.

Function Call

Used to invoke a function from a package:

fmt.Println(...)