concatenation - Anobium/Great-Cow-BASIC-Help GitHub Wiki

Concatenation

Syntax:

    stringvar = variable1 + variable2

Command Availability:

Available on all microcontrollers

Explanation:

The method joins two variables into another variable.

This method does not change the existing strings, but returns a new string containing the text of the joined variables, see Concatenated String Constraint below.

Concatenation joins the elements of a specified values using the specified separator between each variable.

Warning

Using concatenation with commands like HSerPrint, Print the compiler will create a system string variable.  Examples of two strings constants ( HSerPrint "123"+"456" may yield incorrect results.  See the use of SYSDEFAULTCONCATSTRING below  Without using SYSDEFAULTCONCATSTRING there is a risk that the compiler does not allocate sufficient RAM to hold the concatenated string.   The resulting string may be corrupted as the size of the system string variable if not set using SYSDEFAULTCONCATSTRING within the source program.

Set a specific size of compiler created system string variable

Use the following to set the size of compiler created system string variable.  

The compiler will create system string variables when you concatenate on a commands line like HSerPrint, Print and many others commands.   Using concatenate with a command is bad practice, using a lot of RAM and may create a number of system string variables.   It is recommended to define a string (of a known length), concatenate using an assignment then use the string.  

This constraint does not apply using concatenation as an assignment.  

To control the size of system string variable use the following.   Also, use this constant to set the size when the compiler does not create a system string variable.  

    'Define the constant to control the size of system created string variables called SYSSTRINGPARAM1, SYSSTRINGPARAM2 etc.
    Use #DEFINE  SYSDEFAULTCONCATSTRING  4

    'Then, use
    HSerPrint "A"+"123"   'will print A123. Without the SYSDEFAULTCONCATSTRING constant some microcontrollers may corrupt the result of the concatentation.

Example 1:

    timevariable = 999
    stringvar = "Time = " + str(timevariable) ' Convert the timevariable to a String.  This operation returns Time = 999

Example 2:

An example showing how to set a string to an escape sequence for an ANSI terminal.  You can `Dim`ension a string and then assign the elements like an array.

    dim line2 as string
    line2 =  27, "[", "2", "H", 27, "[","K"
    HSerPrint line2

Will send the following to the terminal. <esc>[2H<esc>[K

Note: Concatenated String Constraint @v0.98.00 and prior versions

When concatenating a string you cannot assign a string to itself.  You must assign the result of string concatenation to another string. See below.

Example to resolve string handling constraint:

    dim outstring1, tmpstring as string * 16
    dim outnumber as byte

    outnumber = 24
    outstring1 = "Result = "
    'This concatenation will yield an incorrect string
    outstring1 = outstring1 +str(outnumber)

    'This concatenation will yield an the correct string. With tmpstring1 containing the correct concatenated string
    tmpstring1 = outstring1 +str(outnumber)

To resolve the constraint simply assign the source string to another string.

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