Ruby - Operator Boolean Operators

  1. HOME
  2. Ruby
  3. Operator
  4. Boolean Operators

Introduction

The following operators are available in Ruby for testing expressions that may yield true or false values.

OperatorDescription
and && evaluate the left-hand side; only if the result is true do they then evaluate the right side. and has lower precedence than &&.
or || evaluate the left-hand side; if the result is false, then they evaluate the right side. or has lower precedence than ||.
not ! negate a Boolean value; they return true when false and return false when true.

Because of the difference in precedence, conditions will be evaluated in different orders and may yield different results.

Demo

# Example 1 
if ( 1==3 ) and (2==1) || (3==3) then  
   puts('true')  
else  #   w ww. ja v a  2  s. com
   puts('false')  
end 

# Example 2 
if ( 1==3 ) and (2==1) or (3==3) then  
   puts('true')  
else  
   puts('false')  
end

Result

In fact, Example 1 prints "false," while Example 2 prints "true."

This is because or has lower precedence than ||.

Here, I have rewritten Examples 1 and 2; in each case, the addition of one pair of parentheses has inverted the initial Boolean value returned by the test:

Demo

# Example 1 (b) - now returns true 
if (( 1==3 ) and (2==1)) || (3==3) then  
   puts('true')  
else  # www  .j  a v a  2 s  .com
   puts('false')  
end 

# Example 2 (b) - now returns false 
if ( 1==3 ) and ((2==1) or (3==3)) then  
   puts('true')  
else  
   puts('false')  
end

Result

Related Topics