mirror of
https://github.com/QB64Official/qb64.git
synced 2024-07-16 20:05:14 +00:00
57 lines
1.9 KiB
Markdown
57 lines
1.9 KiB
Markdown
|
The [CVD](CVD) function decodes an 8-byte [STRING](STRING) generated by [MKD$](MKD$) (or read from a file) to [DOUBLE](DOUBLE) numeric values.
|
||
|
|
|
||
|
|
## Syntax
|
||
|
|
|
||
|
|
> result# = [CVD](CVD)(stringData$)
|
||
|
|
|
||
|
|
## Description
|
||
|
|
|
||
|
|
* *CV* functions ([CVD](CVD), [CVS](CVS), [CVI](CVI), [CVL](CVL), [CVDMBF](CVDMBF), [CVSMBF](CVSMBF)) are used to convert values encoded by *MK$* functions ([MKD$](MKD$), [MKS$](MKS$), [MKI$](MKI$), [MKL$](MKL$), [MKDMBF$](MKDMBF$), [MKSMBF$](MKSMBF$)).
|
||
|
|
* Variables of numerical types are also encoded when [PUT](PUT) to a [RANDOM](RANDOM) or [BINARY](BINARY)-access file.
|
||
|
|
* **QB64** has [_CV](_CV) and [_MK$](_MK$) functions which can also deal with extended [Data types](Data-types).
|
||
|
|
* [DOUBLE](DOUBLE) values can range up to 15 decimal point digits. Decimal point accuracy depends on whole value places taken.
|
||
|
|
|
||
|
|
## Example(s)
|
||
|
|
|
||
|
|
Reading an 8-byte encoded string n$ from a file and obtaining the decoded [DOUBLE](DOUBLE) value:
|
||
|
|
|
||
|
|
```vb
|
||
|
|
|
||
|
|
FIELD #1, 8 AS N$, 12 AS B$...
|
||
|
|
GET #1
|
||
|
|
Y# = CVD(N$)
|
||
|
|
|
||
|
|
```
|
||
|
|
|
||
|
|
> *Explanation:* Reads a field from file #1, and converts the first eight bytes (N$) into an double-precision number assigned to the variable Y#.
|
||
|
|
|
||
|
|
Showcases the reduced space to store an encoded number.
|
||
|
|
|
||
|
|
```vb
|
||
|
|
|
||
|
|
a# = 77000.24523213
|
||
|
|
PRINT "Value of a#:"; a#
|
||
|
|
b$ = MKD$(a#)
|
||
|
|
PRINT "Value of a# encoded using MKD$: "; b$
|
||
|
|
PRINT "The string above, decoded using CVD:"; CVD(b$)
|
||
|
|
|
||
|
|
```
|
||
|
|
|
||
|
|
```text
|
||
|
|
|
||
|
|
Value of a#: 77000.24523213
|
||
|
|
|
||
|
|
Value of a# encoded using MKD$: ñåxýâ╠‗@
|
||
|
|
|
||
|
|
The string above, decoded using CVD: 77000.24523213
|
||
|
|
|
||
|
|
```
|
||
|
|
|
||
|
|
> Since the representation of a double-precision number can use up to 15 ASCII characters (fifteen bytes), writing to a file using [MKD$](MKD$) conversion, and then reading back with the [CVD](CVD) conversion can save up to 7 bytes of storage space.
|
||
|
|
|
||
|
|
## See Also
|
||
|
|
|
||
|
|
* [MKD$](MKD$), [MKI$](MKI$), [MKS$](MKS$), [MKL$](MKL$), [MKDMBF$](MKDMBF$), [MKSMBF$](MKSMBF$)
|
||
|
|
* [CVI](CVI), [CVS](CVS), [CVL](CVL), [CVSMBF](CVSMBF), [CVDMBF](CVDMBF)
|
||
|
|
* [_CV](_CV), [_MK$](_MK$)
|