differences between txtadd and += operator

Hi everybody

operator += seems not working properly when the initial var is an empty string or if the string contains only white spaces. Is it normal ?

krpano version 1.21 is used.

have a good day.

	<action name="x" autorun="true" >
		set(a, '');
		def(b, string, ' ');
		
		txtadd(a, 'aaa');  
		b +='bbb';
		trace ('a= ', a, ' b= ', b);    // result is a= aaa b= 0bbb    leading 0 unexpected...
</action>

Hi Tuur

Thanks for your answer. To remove some strangeness for my question, this is extracted from KRPANO doc...

Variable assignments
Syntax:
variable=expression;
With variable assignments new variables can be created or the value of exiting variables be changed.
The expression can be either a simple value or another variable or a more complex expression.
These variable assigment operatos are available:
= - just set/copy the value.
+= - add the value.
-= - subtract the value.
*= - multiple the variable with the given value.
/= - divide the variable by the given value.

and this one extracted from release notes for version 1.21, but OK, not in "official" documentation

New: Support also <action> autorun="true" (same as autorun="onstart").
New: deprecatedwarnings - show a warning when using old deprecated actions.

according to the doc , the real problem is rather the unexpected behavior of += operator for strings...

Last point, i am sorry for my bad english. (i am French...)

thanks Klaus and Tuur