The binary relational operators determine the following relationships:
Syntax
relational-expression :
shift-expression
relational-expression < shift-expression
relational-expression > shift-expression
relational-expression <= shift-expression
relational-expression >= shift-expression
The relational operators have left-to-right associativity. Both operands of relational operators must be of arithmetic or pointer type. They yield values of type int. The value returned is 0 if the relationship in the expression is false; otherwise, it is 1. Consider the following code, which demonstrates several relational expressions:
#include <iostream.h>
void main()
{
cout << "The true expression 3 > 2 yields: "
<< (3 > 2) << "\n";
cout << "The false expression 20 < 10 yields: "
<< (20 < 10) << "\n";
cout << "The expression 10 < 20 < 5 yields: "
<< (10 < 20 < 5) << "\n";
}
The output from this program is:
The true expression 3 > 2 yields 1
The false expression 20 < 10 yields 0
The expression 10 < 20 < 5 yields 1
The expressions in the preceding example must be enclosed in parentheses because the insertion operator (<<) has higher precedence than the relational operators. Therefore, the first expression without the parentheses would be evaluated as:
(cout << "The true expression 3 > 2 yields: " << 3) < (2 << "\n");
Note that the third expression evaluates to 1 — because of the left-to-right associativity of relational operators, the explicit grouping of the expression 10 < 20 < 5 is:
(10 < 20) < 5
Therefore, the test performed is:
1 < 5
and the result is 1 (or true).
The usual arithmetic conversions covered in Arithmetic Conversions in Chapter 3 are applied to operands of arithmetic types.