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+--- Thread: Equation stored in variable, then used by Solver (/thread-1249.html)
Equation stored in variable, then used by Solver - Alfon - 05-05-2014 10:59 PM
Is there a way to store an equation in a variable, then use the solve application to retrieve this equation from the variable and then solve it?
RE: Equation stored in variable, then used by Solver - Han - 05-06-2014 01:08 AM
You can save the equation in a string. Likewise, I would consider a separate string for the variables.
E.g.
Code:
// formula: F=ma; we'll use the global variable F and create m and a as needed
vars:={ "m", "a" };
eqns:="F=m*a";
// initialize solver
local cmd,i, n:=SIZE(vars);
for i from 1 to n do
cmd:=vars(i) + ":=0"; // set initial value to 0;
CAS(cmd); // call CAS to evaluate cmd as if run from command line
end;
E1:=eqns; // set E1
// … code here to start the app, see STARTAPP() or STARTVIEW()
// clean up, if needed
for i from 1 to d no
cmd:="purge(" + vars(i) +")"; // create a purge command
CAS(cmd); // purge the variable
end;These routines can easily to combined into a solver app to build an actual equation library with complete support for custom equations and variables. I'm currently working on one, but have been sidetracked with several other projects…
RE: Equation stored in variable, then used by Solver - Angus - 05-06-2014 07:17 AM
Han, is that part of program code? What did you show? How would you use it? Do you -have- to store equations to a global, capitalized variable F? Do you assign the variable list m,a and the equation prior to program start?
A working example with additional comments would be beneficial. Thanks.
RE: Equation stored in variable, then used by Solver - CR Haeger - 05-06-2014 12:03 PM
I have saved formulas into CAS variables, defined solve.E1:='CAS variable' (a formula) then used Solver.
Here is a thread about this: http://www.hpmuseum.org/forum/thread-955.html
Best,
Carl
RE: Equation stored in variable, then used by Solver - Angus - 05-06-2014 12:15 PM
Thank you, I remember your thread. You don't use any strings, I see? Copying over a note to the cas is not really user friendly. :-(
I had the feeling Han tried to add more automation on the one hand and on the other I feel like that is an example to learn to avoid issues when programming the calculator.
What is about string usage and no string usage. I studied the patch notes and did not notice any changes concerning these topics (that is data handling) so there is a need to get used to how things are now. They are likely to last.....
I might be old or I might not have enough time for the calculator there is even the chance of being too stupit, but I did not really understand this device. I can play with it, I find interessting aspects, but once I really need it I get stuck and can't find the right way to work with it. It still did not become a tool, it is still a toy which frustrates me.