Campbell-scientific CR1000 Measurement and Control System Manual de usuario descargar pdf (Pagina 494)

100

101

Appendix A. CRBasic Programming Instructions

494

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The result of these operators is the value of the left hand operand with all of its

bits moved by the specified number of positions. The resulting "holes" are filled

with zeroes.

Consider a sensor or protocol that produces an integer value that is a composite of

various "packed" fields. This approach is quite common to conserve bandwidth

and/or storage space. Consider the following example of an eight-byte value:

• bits 7-6: value_1

• bits 5-4: value_2

• bits 3-0: value_3

Code to extract these values is shown in CRBasic example Using Bit-Shift

Operators

(p. 494).

With unsigned integers, shifting left is equivalent to multiplying by two. Shifting

right is equivalent to dividing by two.

<<

Bitwiseleftshift

Syntax

Variable = Numeric Expression >> Amount

>>

Bitwiserightshift

Syntax

Variable = Numeric Expression >> Amount

&

BitwiseANDassignment‐‐PerformsabitwiseANDofavariablewithan

expressionandassignstheresultbacktothevariable.

A.6.4 Compound-assignment operators

Table 117. Compound-Assignment Operators

Symbo

Name Function

Exponent

assignment

Raises the value of a variable to the power of an expression and

assigns the result back to the variable.

Multiplication

assignment

Multiplies the value of a variable by the value of an expression and

assigns the result to the variable.

Addition

assignment

Adds the value of an expression to the value of a variable and

assigns the result to the variable. Also concatenates a String

expression to a String variable and assigns the result to the

variable.

Subtraction

assignment

Subtracts the value of an expression from the value of a variable

and assigns the result to the variable.

Division

assignment

Divides the value of a variable by the value of an expression and

assigns the result to the variable.

Division integer

assignment

Divides the value of a variable by the value of an expression and

assigns the integer result to the variable.

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