DOUBLE Function

Reference Guide > D Routines > DOUBLE Function

DOUBLE Function

The DOUBLE function does the following:

Converts an expression to double-precision floating-point data type.

Extracts data from an expression and places it in a double-precision floating-point scalar or array.

enabled.

Usage

This form is used to convert data:

result = DOUBLE(expr)

This form is used to extract data:

result = DOUBLE(expr, offset, [dim1, ..., dimn ])

Input Parameters

To convert data:

expr — The expression to be converted.

To extract data:

expr — The expression from which to extract data.

offset — The offset, in bytes, from the beginning of expr to where the extraction is to begin.

dimi — (optional) The dimensions of the result. May be any scalar expression. Up to eight dimensions may be specified.

Returned Value

For data conversion:

result — A copy of expr converted to double-precision floating-point data type.

For data extraction:

result — If offset is used, DOUBLE does not convert result, but allows fields of data extracted from expr to be treated as double-precision floating-point data. If no dimensions are specified, the result is scalar.

Keywords

None.

Example

In this example, DOUBLE is used in two ways. First, DOUBLE is used to convert an integer array to double precision, floating point. Next, DOUBLE is used to extract a subarray from the double precision array created in the first step.

; Create an integer vector of length 6 that is initialized to the

; a = INDGEN(6) value of its one-dimensional subscript.

a = INDGEN(6)

PRINT, a

; PV-WAVE prints: 0  1  2  3  4  5

; Convert a to double precision, floating point.

b = DOUBLE(a)

INFO, b

; PV-WAVE prints: B       DOUBLE    = Array(6)

PRINT, b

; PV-WAVE prints:

;   0.00000000    1.0000000    2.0000000    3.0000000

;   4.0000000     5.0000000

; Extract the last four elements of b, and place them in

; a 2-by-2 double-precision, floating-point array.

c = DOUBLE(b, 16, 2, 2)

INFO, c

; PV-WAVE prints: C           DOUBLE    = Array(2, 2)

PM, c

; PV-WAVE prints:

;    2.0000000      4.0000000

;    3.0000000      5.0000000

note	If you want to place the double-precision value of a constant into a variable, it is much better to use the d or D constant notation rather than the double function. Because passing a float to the DOUBLE function will not produce the desired precision. For example: x = .0705230784D