HP Prime and Strings  Printable Version + HP Forums (https://archived.hpcalc.org/museumforum) + Forum: HP Museum Forums (https://archived.hpcalc.org/museumforum/forum1.html) + Forum: Old HP Forum Archives (https://archived.hpcalc.org/museumforum/forum2.html) + Thread: HP Prime and Strings (/thread250753.html) 
HP Prime and Strings  Han  09192013 Since the HP Prime is able to handle strings, is it possible to take strings and convert them into functions? I know back in the TI85 there was such a command. Does/will the HP Prime have the ability to ask users to input a function to be used as a symbolic object like equations in the HP48 series?
I tried using the INPUT command but it seems to only accept numerical inputs.
Re: HP Prime and Strings  Eddie W. Shore  09192013 What I found to be the most successful is to pass functions as strings as arguments. Example:
\\ calculate the numerical derivative of f(X) at X = N f(X) = 3*e^X  3*X^2. Find f'(1). NDER("3*e^X  3*X^2",1) returns 2.15484. We could also use strings to store functions into graphing functions or equations. Example: "3*X+4"  > F1 Hope this helps, Eddie
Re: HP Prime and Strings  Gilles Carpentier  09192013
Quote: INPUT allows all type of argument but you have put the right delimiters: " " [ ] { } etc. be carefull that A..Z variables are only numericals
The INPUT command is very powerfull (default value, on line help ...)
Re: HP Prime and Strings  Han  09192013 Could you give me an example of how to ask the user to enter in a function that can be used as a function? Ideally I would like to have something like: f(x,y)=
and have the user enter in a formula that can be used later on.
Re: HP Prime and Strings  Namir  09202013 Here is an example of a Newton method that uses a string parameter sFx to pass a string image for a function:
EXPORT Newton(sFx,xguess,toler)
Samples calls are: Newton("EXP(X)3*X^2",1,.00000001) The function uses the predefined variable X to store values of xguess (the guess for the root) and xguess+h, before calling function EXPR(sFx).
Namir
Re: HP Prime and Strings  Han  09202013 Thank you for sharing your example, Namir. What I was looking for in particular, however, was an example on how to use INPUT in order to get a function. My goal is to create an interactive app, as opposed to a function like yours in which everything is entered at once. My attempt below results in an inputformlike interface (much like the HP48 series) but the default value is 0, and not a formula.
EXPORT EXAMPLE() INPUT(F,"Graph 3D","f(x,y)=","Enter the function to graph","1/390*(X^3*YX*Y^3"); END; If I do enter a new formula "X*Y" or 'X*Y'  with the quotes  I get a syntax error. If I take out the quotes, then (as expected), the value of F is whatever X*Y is equal to the moment the program was run. However, this is not what I want, since I cannot evaluate F at different values of X and Y later within my program. Secondly, if such a procedure should work, then presumably F is a string. How would I then convert a string object into a function?
Edited: 20 Sept 2013, 10:16 a.m.
Re: HP Prime and Strings  Han  09202013 Quote:
To clarify, I was not referring the the arguments of the INPUT command. Instead the INPUT command  when in use  seems to only allow the user to enter in numerical values when the program is running.
