Basics of Operators & Expressions

In Go programming, operators are symbols or combinations of symbols that perform various operations on values or variables.

An expression is a combination of values and operators that yield an evaluated value. For example, 7 + 9 is an expression that yields 16, and 7 * 9 is an expression that yields 63, as the * operator represents multiplication.

In this chapter, we will explore the Arithmetic operators. Most of the remaining operators will be discussed in subsequent sections, as relevant.

Operator	Function
`+`	Addition
`-`	Subtraction
`*`	Multiplication
`/`	Division
`%`	Remainder(Mod)
`++`	Increment
`--`	Decrement

Studying the following code and its corresponding outputs can be a valuable exercise in code comprehension. All the arithmetic operators are elucidated within the code using comments, along with the respective output.

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package main
import "fmt"
 
func main() {
 
	// Addition
	fmt.Println("Addition (7 + 9):", 7+9) // Outputs 16
 
	// Subtraction
	fmt.Println("Subtraction (7 - 9):", 7-9) // Outputs -2
 
	// Multiplication
	fmt.Println("Multiplication (7 * 9):", 7*9) // Outputs 63
 
	// Division
	fmt.Println("Division (10 / 2):", 10/2) // Outputs 5
	fmt.Println("Division (7 / 9):", 7/9)   // Outputs 0, reason will be explained in the next section
 
	// Remainder (Modulus)
	fmt.Println("Mod (10 % 2)", 10%2) // Outputs 0
	fmt.Println("Mod (10 % 3)", 10%3) // Outputs 1
	fmt.Println("Mod (10 % 4)", 10%4) // Outputs 2
 
	var myVar = 1
	fmt.Println("Value:", myVar) // Outputs 1
 
	// Increment Operator (++)
	// Increases a variable's value by 1
	myVar++
	fmt.Println("Value (after ++):", myVar) // Outputs 2
 
	// Decrement Operator (--)
	// Decreases a variable's value by 1
	myVar--
	fmt.Println("Value (after --)", myVar) // Outputs 1
}

By default, in Go, expressions are evaluated using the BODMAS (also known as PEMDAS) rule. According to this rule, an expression is evaluated in the following order:

Brackets;

Exponents;

Division;

Multiplication;

Addition;

Subtraction;

Consider the expression 1 + 3 * 4 / 2. The order of evaluation and the result are as follows:

1 + 3 * 4 / 2 → 1 + 3 * 2 → 1 + 6 → 7

Hence, fmt.Println(1 + 3 * 4 / 2) outputs 7.

We can use brackets to change the order of operations and, consequently, the result:

(1 + 3) * 4 / 2 → 4 * 4 / 2 → 4 * 2 → 8

Brackets can also be nested for more precise control of operations:

((1 - 3) + 4) / 2 → (-2 + 4) / 2 → 2 / 2 → 1

In the above case, subtraction was performed first, followed by addition, and then division.

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Seção 1. Capítulo 7