CVD - QB64Official/qb64 GitHub Wiki

The CVD function decodes an 8-byte STRING generated by MKD$ (or read from a file) to DOUBLE numeric values.

Syntax

result# = CVD(stringData$)

Description

CV functions (CVD, CVS, CVI, CVL, CVDMBF, CVSMBF) are used to convert values encoded by MK$ functions (MKD$, MKS$, MKI$, MKL$, MKDMBF$, MKSMBF$).
Variables of numerical types are also encoded when PUT to a RANDOM or BINARY-access file.
QB64 has _CV and _MK$ functions which can also deal with extended Data types.
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 value:


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.


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$)


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$ conversion, and then reading back with the CVD conversion can save up to 7 bytes of storage space.