Supplementing Generated Ada : Detecting Changes in Value

Detecting Changes in Value

If the event expression ch(), tr() or fs() is applied to an expression that uses a Data-Item or condition, it is necessary to preserve the previous value of the element. This is done by maintaining a duplicate copy of the element that is updated at the end of every step. (This makes detecting ch() on a large array or complex record a very slow process, because it takes time on every step.) The duplicate copy of the variable is named prev_<element>.

The following table lists the affected element types:

 
define base Data-Item
Note:  

Element—is the name of the element as listed in the .info file. This is normally the same as the Element Name in the Properties, unless there are duplicate Element Names.

Type—is the name of the User-Defined Type. It is also listed in the info file.