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Number datatype


Pointer2.png How to combine two numbers to one and vice versa Pointer.png

To combine two numbers into one, use the next function

   nCombined = VisNumberMakeLong( nValue1, nValue2 )

You can find this function in vtmisc.apl
Beware that the two input parameters must have a value between 0 and 65535.

To get the two values back from the combined number

   Set nValue1= SalNumberLow( nCombined )
   Set nValue2= SalNumberHigh( nCombined )

Pointer2.png How to convert a number to string using prefixed zeros Pointer.png

An easy way to do that is using this function

   sResult = SalFmtFormatNumber( nValue, sPicture )

So if you want to have a string with 5 characters and if nValue results in less characters and should be prefixed with zeros

   Set nValue = 12
   Set sResult = SalFmtFormatNumber( nValue, "00000" )      ! Picture parameter has 5 zeros specified

   ! sResult has the value "00012"

Pointer2.png An alternative way to define a number in boolean expressions Pointer.png

Look at the next piece of code

   If bOk = TRUE
      Set nValue = 1
      Set nValue = -1

It can be rewritten using one line of code using this function from vtmisc.apl

   nResult = VisNumberChoose( bExpression, nTrueNumber, nFalseNumber )

So the If/Else construction above can be rewritten to

   Set nValue = VisNumberChoose( bOk = TRUE, 1, -1 )

See also:

MediaWikiLink.png String : An alternative way to define a string in boolean expressions

Pointer2.png How to convert from one base to another (eg decimal to hexadecimal to binary) Pointer.png

Developers familiar with the C(++) language will probably know conversion functions like itoa and strtol.
The itoa function (integer to ASCII) is able to convert/format a decimal integer number to a given base (eg hexadecimal, binary, octal etc).
The function strtol does the opposite, converting a base to decimal.

These functions are also available to other programming languages with the MSCRT library (C runtime).
So also for TD.

First declare these external functions (below the declarations for TD versions prior to TD5.1, ANSI) :

Library name: MSVCRT.dll
   Function: _itoa
      Export Ordinal: 0
         Number: INT
         Receive String: LPSTR
         Number: INT
   Function: strtol
      Export Ordinal: 0
         Number: LONG
         String: LPCSTR
         Number: LPVOID
         Number: INT

Below the declarations for TD 5.1 and higher versions (UNICODE) :

Library name: MSVCRT.dll
   Function: _itow
      Export Ordinal: 0
         String: LPWSTR
         Number: INT
         Receive String: LPWSTR
         Number: INT
   Function: wcstol
      Export Ordinal: 0
         Number: LONG
         String: LPCWSTR
         Number: LPVOID
         Number: INT

See more info concerning these CRT functions on MSDN:

Web.png _itoa, _i64toa, _ui64toa, _itow, _i64tow, _ui64tow
Web.png strtol, wcstol, _strtol_l, _wcstol_l

The next piece of code converts a decimal integer to the given base

   Call SalStrSetBufferLength( sBuffer, 32 )
   ! Set nToBase to 2..36 (2 = binary, 8 = octal, 10 = decimal, 16 = hexadecimal)
   Call _itoa( nDecimalNumber, sBuffer, nToBase )
   ! sBuffer holds the converted decimal in the given base

Here the code to convert a base number to decimal

   Set nNumber = strtol( sBaseValue, NUMBER_Null, nBase )


   ! Next, decimal to hexadecimal
   Call _itoa( 125, sBuffer, 16 )
   ! sBuffer = "7d"
   ! Next, decimal to octal
   Call _itoa( 125, sBuffer, 8 )
   ! sBuffer = "175"
   ! Next, decimal to binary
   Call _itoa( 125, sBuffer, 2)
   ! sBuffer = "1111101"
   ! Next, binary to decimal
   Set nNumber = strtol( "101, NUMBER_Null, 2 )
   ! nNumber = 5

Using these functions you are able to convert from one base to another.

The sample can be downloaded below, it uses wrapper PAL functions for the CRT functions and a Base2Base function.
(Separate samples for TD5.1 and higher also provided).


Pointer2.png Endianness in TD: Little-endian vs Big-endian Pointer.png

In computing, memory commonly stores binary data by splitting it into 8 bit units (bytes).
When a data word uses multiple such units, the order of storing these bytes into memory becomes important.
The terms endian and endianness, refer to how bytes of a data word are ordered within memory.

Windows (and TD) is using Little-endian to store the sequence of bytes in memory.

Let's compare the two endianesses:
Assume we have a 32 bit number (= 4 bytes) value represented as hex value : 0xAABBCCDD

A TD number value will be stored as Little-endian which look like this :


The same value in Big-endian looks like this:


The difference is the sequence from left to right where the bytes are stored.

When you need to use Big-endian numbers, for instance when sending data to an external system which uses Big-endian sequence
you need to convert the TD Little-endian buffer to Big-endian before sending it.
When you send the Little-endian style, the receiving party will interpret the data incorrectly.
And also the way back. receiving Big-endian data will be wrongly interpreted by TD. You first have to convert the value
to Little-endian before using it.

To convert a TD number to Big-endian and back to Little-endian, use the WinApi functions in the WinSock library.
With the functions htons (16 bits value), htonl (32 bits value) you convert Little-endian to Big-endian.
With the functions ntohs (16 bits value), ntohl (32 bits value) you convert Big-endian to Little-endian.

Look at the sample application which shows how to implement this.