Han...question about your eqnlib app.

[webmasterpdx]

I notice that when this app is selected, when in CAS mode, I tried to see what the value of x was, and it says 0. Then I typed purge(x) and it says x doesn't exist....but x returns 0 every time. I eventually discovered it was due to the eqnlib app being selected. When I selected another app, x disappeared....

Why is this?
Thx
-Donald

[Han]

(11-17-2017 06:43 AM)webmasterpdx Wrote:  I notice that when this app is selected, when in CAS mode, I tried to see what the value of x was, and it says 0. Then I typed purge(x) and it says x doesn't exist....but x returns 0 every time. I eventually discovered it was due to the eqnlib app being selected. When I selected another app, x disappeared....

Why is this?
Thx
-Donald

It is likely because your system of equations uses the variable x. When you create a system of equations, the app tries to automate the creation of variables when it can, or forces you to create a variable when it cannot. In the latter case, it creates an app variable via:

AVars("nameofvariable"):=0;

once you declare the variable name and sets its default value to 0. App variables are specific to only that app. The variable remains until a new system is selected/created in which x is no longer a variable. The app tries to keep track of the usage of x -- if after a while it detects that x has become stale, it will also delete it then using:

DelAVars("nameofvariable");