Four Ways of Writing Go Iteration

Go Iteration

Iteration in programming referring to the action that is keep repeating of an instruction, and known as Loop.

For statement

In Go programming language, there is no while or do-while statement, they are all unified as for statement.

There are three ways to write a for statement.

// With init, condition and post
for i := 0; i < 10; i++ {
    sum += i
}

// Only condition
b := true
for b {
	b = false
}

// for without a condition
for {
	break
}

Range statement

Range is similar like foreach loop in a way. Below is the clause from the The Go Programming Language Specification for the For Statement

A "for" statement with a "range" clause iterates through all entries of an array, slice, string or map, or values received on a channel. For each entry it assigns iteration values to corresponding iteration variables if present and then executes the block.

Loop for a index and value

for index, value := range m {

}

Loop for a key and value

for k, v := range m {
	
}

Loop for the first item

for k := range m {
	
}

Loop for the second item

for _, v := range m {
    
}

Caveats

According to the Effective Go documentation, for statement in Go has no,

• comma operator and

• ++ and -- are statements not expressions

Below is the clause from the The Go Programming Language Specification for the For Statement

Finally, Go has no comma operator and ++ and -- are statements not expressions. Thus if you want to run multiple variables in a for you should use parallel assignment (although that precludes ++ and --).

Hence, multiple variables should be used in a for statement.

for i < 10 {
    // Syntax error: unexpected ++ at end of statement
	sum = j++
	// Syntax error: unexpected ++, expecting expression
	sum = ++j
	// Valid Expression
	sum += j
}

However that precludes ++ and --