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In this chapter we will cover the basics of using operators in Ruby to build expressions. Ruby provides a number of different types of operators including:

* Assignment Operators
* Math Operators
* Comparison Operators
* Bitwise Operators


== The Anatomy of a Ruby Operation ==

In Ruby, as with most other programming languages, operations consist of values on which the calculation is to be performed (called ''operands'') and an ''operator'' which dictates the operation to be performed. Typically, the ''operands'' are placed either side of the ''operator''. Optionally, the ''assignment'' operator (=) can be used to assign the result of the operation to, for example, a variable. Let's take the most basic of operations, executed in ''irb'':

<pre>
irb(main):036:0> 1 + 1
=> 2
</pre>

Now let's assign the result to a variable called ''result'':

<pre>
irb(main):037:0> result = 1 + 1
=> 2
</pre>

== Performing Ruby Arithmetic using Operators ==
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Ruby provides a number of basic operators for performing arithmetic. These are as follows:

<table border="1" cellspacing="0">
<tr style="background:#efefef;">
<th>Operator</th><th>Description</th>
<tr>
<td>+<td>Addition -  Adds values on either side of the operator </td>
<tr>
<td>-<td>Subtraction - Subtracts right hand operand from left hand operand </td>
<tr>
<td>*<td>Multiplication - Multiplies values on either side of the operator </td>
<tr>
<td>/<td>Division - Divides left hand operand by right hand operand</td>
<tr>
<td>%<td>Modulus - Divides left hand operand by right hand operand and returns remainder</td>
<tr>
<td>**<td>Exponent - Performs exponential (power) calculation on operators</td>
</tr>
</table>

Note that when performing division, if you do not want the result to be truncated to a round number, one of the operands in the operation must be expressed as a float:

<pre>
irb(main):001:0> 10 / 7
=> 1
</pre>

In the above example the result has been rounded down to the nearest whole number. On the other hand, if we express one of the operands as a float, we get a more accurate answer:

<pre>
irb(main):003:0> 10.0 / 7
=> 1.42857142857143
</pre>

== Ruby Assignment Operators ==

Earlier in this chapter we looked the basic assignment operator (=) which allows us to assign the result of an expression, for example ''y = 10''.

The '=' assignment operator does not make any changes to the value before it is assigned to the variable. A number of assignment operators are available, however, that perform arithmetic on the value before assigning it to the variable. These are essentially combined arithmetic and assignment operators. The most common operators of this type, and their "long hand" equivalents are shown below:

<table border="1" cellspacing="0">
<tr style="background:#efefef;">
<th>Combined Operator<th>Equivalent</th>
</tr>
<tr>
<td>x += y<td>x = x + y</td>
<tr>
<td>x -= y<td>x = x - y</td>
<tr>
<td>x /= y<td>x = x / y</td>
<tr>
<td>x *= y<td>x = x * y</td>
<tr>
<td>x %= y<td>x = x % y</td>
<tr>
<td>x **= y<td>x = x ** y</td>
</table>

These combined operators provide a short way of assigning the results of arithmetic expressions between two variables or a variable and a value and having the result assigned to the first variable. For example:

<pre>
x = 10
x += 5 # Assigns a value of 15 to variable x (the same as x = x + 5)

y = 20
y -= 10  # Assigns a value of 10 to variable y (the same as y = y - 10)

x = 10;
y = 5;

x /= y; # Assigns a value of 2 to variable x (the same as x = x / y)
</pre>

== Parallel Assignment ==

Ruby also supports the parallel assignment of variables. This enables multiple variables to be initialized with a single line of Ruby code. For example:

<pre>
a = 10
b = 20
c = 30
</pre>

The above code may be more quickly declared using parallel assignment:

<pre>
a, b, c = 10, 20, 30
</pre>

Parallel assignment is also useful for swapping the values held in two variables:

<pre>
a, b = b, c
</pre>

== Ruby Comparison Operators ==

Comparison operators are used to check for equality between two values. Ruby provides a number of such operators:

<table width="100%" border="1" cellspacing="0">
<tr style="background:#efefef;">
<th>Comparison Operator<th>Description</th>
</tr>
<tr>
<td>==<td>Tests for equality. Returns ''true'' or ''false''</td>
<tr>
<td>.eql?<td>Same as ==.</td>
<tr>
<td>!=<td>Tests for inequality. Returns ''true'' for inequality or ''false'' for equality</td>
<tr>
<td><<td>Less than. Returns ''true'' if first operand is less than second operand. Otherwise returns ''false''</td>
<tr>
<td>><td>Greater than. Returns ''true'' if first operand is greater than second operand. Otherwise returns ''false''.</td>
<tr>
<td>>=<td>Greater than or equal to. Returns ''true'' if first operand is greater than or equal to second operand. Otherwise returns ''false''.</td>
<tr>
<td><=<td>Less than or equal to. Returns ''true'' if first operand is less than or equal to second operand. Otherwise returns ''false''.</td>
<tr>
<td><=><td>Combined comparison operator. Returns 0 if first operand equals second, 1 if first operand is greater than the second and -1 if first operand is less than the second.</td>
</table>

Let's look at some of these operators in action:

<pre>
irb(main):006:0> 1 == 1
=> true

irb(main):015:0> 1.eql? 2
=> false

irb(main):016:0> 10 < 1
=> false

irb(main):019:0> 10 <=> 10
=> 0

irb(main):020:0> 10 <=> 9
=> 1

irb(main):021:0> 10 <=> 11
=> -1
</pre>

== Ruby Bitwise Operators ==

Bitwise operators allow operations to be performed on number at the bit level. As you are probably already aware, computers deal solely with binary (in other words ones and zeros). For example, the computer sees the number 520 as 01010. 

The Ruby bitwise operators allow us to operate at the level of the ones and zeros that make up a number:

<table border="1" cellspacing="0">
<tr style="background:#efefef;">
<th>Combined Operator<th>Equivalent</th>
</tr>
<tr>
<td>~<td>Bitwise NOT (Complement)</td>
<tr>
<td>|<td>Bitwise OR</td>
<tr>
<td>&<td>Bitwise AND</td>
<tr>
<td>^<td>Bitwise Exclusive OR</td>
<tr>
<td><<<td>Bitwise Shift Left</td>
<tr>
<td>>><td>Bitwise Shift Right</td>
</table>

As with the math operators, Ruby also provides a number of combined bitwise operators (for example ~=, >>=, <<= ^=, &=).

== Summary ==

In this chapter of [[Ruby Essentials]] we have covered the basics of Ruby operators, expressions and assignments. In the next chapter we will look at the all important area of [[Ruby Operator Precedence]].


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<hr>
<table border="0" cellspacing="0" width="100%"><tr>
<td width="20%">[[Advanced Ruby Arrays|Previous]]<td align="center">[[Ruby Essentials|Table of Contents]]<td width="20%" align="right">[[Ruby Operator Precedence|Next]]</td>
<tr>
<td width="20%">Advanced Ruby Arrays<td align="center"><td width="20%" align="right">Ruby Operator Precedence</td>
</table>