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Publication 2098-PM001E-EN-P — July 2002

Programming Motion Control in C 1-21

Relational and Logical

Operators

The relational operators (<, <=, >=, >) make comparisons that test

expressions. They have lower precedence than arithmetic operators,

but higher precedence than the equality operators (==, !=). The logical

operators (&& and ||) have a lower precedence than either the

relational operators and equality operators.

Each of these operators (except the unary !) compares the value to the

left of the operator to the value at its right.

The table below lists the precedence and describes the functions of

these operators.

The numeric value of relational and logical expressions is 1 if the

relation is true, and 0 if the relation is false. The unary negation

operator ! converts a non-zero operand into 0 and a zero operand into

1.

Conditional Expressions

Conditional expressions are a compact way of writing if-else

statements using “?”, the ternary operator. (If-Else is introduced on

page 1-24.)

The operator requires three operands, each of which is an expression,

and the condition is evaluated from left to right.

expressionl ? expression2 : expression3

The value of the whole expression equals the value of expression2 if

expression1 is true, else it equals the value of expression3.

Operator: Precedence: Function: Limitations:

< 1 Is less than

<= Is less than or equal to Rounding may cause

errors with floating

point numbers.

(e.g., 3 * 1/3 is 1, but 3

* 0.333333 is

0.999999).

>= Is greater than or equal to

> Is greater than

== 2 Is equal to

!= Is not equal to

&& 3 And

|| 4 Or

!

(unary form)

5Not

1 2 ... 28 29 30 31 32 33 34 35 36 37 38 ... 113 114

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