Go - Basic Syntax

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We discussed the basic structure of a Go program in the previous chapter. Now it will be easy to understand the other basic building blocks of the Go programming language.

Tokens in Go

A Go program consists of various tokens. A token is either a keyword, an identifier, a constant, a string literal, or a symbol. For example, the following Go statement consists of six tokens −

fmt.Println("Hello, World!")

The individual tokens are −

fmt
.
Println
(
   "Hello, World!"
)

Line Separator

In a Go program, the line separator key is a statement terminator. That is, individual statements don't need a special separator like ; in C. The Go compiler internally places ; as the statement terminator to indicate the end of one logical entity.

For example, take a look at the following statements −

fmt.Println("Hello, World!")
fmt.Println("I am in Go Programming World!")

Comments

Comments are like helping texts in your Go program and they are ignored by the compiler. They start with /* and terminates with the characters */ as shown below −

/* my first program in Go */

You cannot have comments within comments and they do not occur within a string or character literals.

Identifiers

A Go identifier is a name used to identify a variable, function, or any other user-defined item. An identifier starts with a letter A to Z or a to z or an underscore _ followed by zero or more letters, underscores, and digits (0 to 9).

identifier = letter { letter | unicode_digit }.

Go does not allow punctuation characters such as @, $, and % within identifiers. Go is a case-sensitive programming language. Thus, Manpower and manpower are two different identifiers in Go. Here are some examples of acceptable identifiers −

mahesh      kumar   abc   move_name   a_123
myname50   _temp    j      a23b9      retVal

Keywords

The following list shows the reserved words in Go. These reserved words may not be used as constant or variable or any other identifier names.

Whitespace in Go

Whitespace is the term used in Go to describe blanks, tabs, newline characters, and comments. A line containing only whitespace, possibly with a comment, is known as a blank line, and a Go compiler totally ignores it.

Whitespaces separate one part of a statement from another and enables the compiler to identify where one element in a statement, such as int, ends and the next element begins. Therefore, in the following statement −

var age int;

There must be at least one whitespace character (usually a space) between int and age for the compiler to be able to distinguish them. On the other hand, in the following statement −

fruit = apples + oranges;   // get the total fruit

No whitespace characters are necessary between fruit and =, or between = and apples, although you are free to include some if you wish for readability purpose.

Variable Definition

A variable definition tells the compiler where and how much storage to create for the variable. Here is the syntax:

var variable_list optional_data_type;

The if statement

An if statement consists of a boolean expression followed by one or more statements.

if(boolean_expression) {
   /* statement(s) will execute if the boolean expression is true */
}

The if else statement

The syntax of an if...else statement in Go programming language is:

if(boolean_expression) {
   /* statement(s) will execute if the boolean expression is true */
} else {
   /* statement(s) will execute if the boolean expression is false */
}

The nested if statements

The syntax for a nested if statement is as follows:

if( boolean_expression 1) {
   /* Executes when the boolean expression 1 is true */
   if(boolean_expression 2) {
      /* Executes when the boolean expression 2 is true */
   }
}

The switch statement

The syntax for expression switch statement in Go programming language is as follows:

switch(boolean-expression or integral type){
   case boolean-expression or integral type :
      statement(s);      
   case boolean-expression or integral type :
      statement(s); 
   
   /* you can have any number of case statements */
   default : /* Optional */
      statement(s);
}

The select statement

The syntax for a select statement in Go programming language is as follows:

select {
   case communication clause  :
      statement(s);      
   case communication clause  :
      statement(s); 
   /* you can have any number of case statements */
   default : /* Optional */
      statement(s);
}

The for Loop

A for loop is a repetition control structure. It allows you to write a loop that needs to execute a specific number of times.

The syntax of for loop in Go programming language is:

for [condition |  ( init; condition; increment ) | Range] {
   statement(s);
}

The nested for loops

The nested for loops allows to use one loop inside another loop. The following section shows a few examples to illustrate the concept:

The break, continue, and goto statements

These control statements change an execution from its normal sequence.

break

The syntax for a break statement in Go is as follows:

break;

continue

The syntax for a continue statement in Go is as follows:

continue;

goto

The syntax for a goto statement in Go is as follows:

goto label;
..
.
label: statement;