ACR Electronics FPR-10 PROGRAMMER Manuel télécharger pdf (Page 61)

Parker Hannifin

Programming Basics 61

Parentheses

Using parentheses, you can group operations in an expression to

change the order in which they are performed.

Operational Order

For example, the expression

4 + 6 / 2

provides the answer 7, and not 5, because division performs before

addition. When a mathematical expression contains operators that

have the same rank, operations are performed left to right. For

example, in the expression

2 + 6 / 3 * 5 - 9

division and multiplication perform before addition and subtraction.

The first operation is 6 / 3; the second operation multiplies the result

2 by 5, which results as 10. In the third operation, add 2 to 10, which

results as 12. In the fourth operation, subtract 9 from 12 to produce

the final answer of 3.

By using parentheses, you can change the order of operations in an

expression. That is, operations in parentheses are performed first,

then operations outside the parentheses. For example, the

expression

(2 + 6 / 3) * 5 - 9

results in an answer of 11, while the expression

(2 + 6 / 3) * (5 - 9)

results in -16 as the answer.

Nested Parentheses

You can also embed parentheses, where operations in the deepest

parentheses are performed first. For example, the expression

((7 + 3) / 2) * 3

contains embedded parentheses. From the example, the first

operation is 7+3, the second operation is 10/2, and the third

operation is 5*3, which results in 15 as the answer.

Examples

The following demonstrate some simple uses of expressions. The

examples assume memory space is allocated for the variables.

Example 1

The following causes axis X to move position to the resulting value of

the expression.

X(P0 + P2 * P30)

1 2 ... 56 57 58 59 60 61 62 63 64 65 66 ... 198 199

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ACR Electronics FPR-10 PROGRAMMER Manuel Page 61