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+--- Thread: Han...question about your eqnlib app. (/thread-9511.html)
Han...question about your eqnlib app. - webmasterpdx - 11-17-2017 06:43 AM
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
RE: Han...question about your eqnlib app. - Han - 11-17-2017 03:55 PM
(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");