help with program please

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help with program please

pipapowerpongo 17 Jun 2009 19:26

hy everybody,

i'm new in ti basic programming so my queston may be a bit stupid but i'm glad for any help
i wanted to wrtie a prog to read a matrix that i can/could use as a subprogramm

so imagine i have created a matrix with " newmat(3,3)->A
so the matrix A is filled with zeroes

now i want to start the prog readmat(A) that asks step by step the components of A

now my problem: my program works in the way that i can create the new matrix but it has a different name ( in my case it is "mat" but i want the name to be the name as it were before so "A"

how i get the "mat" into "A" inside the program
thanks a lot in advance

readmat(mat)
prgm
dim(mat)->d
d[1]->k
d[2]->l
for i,1,k,1
    for j,1.l.1
        input x
        x->mat[i,j]
    end for
end for
endprgm

Re: help with program please

DarkerLine 17 Jun 2009 19:51

The indirection command, #, does what you want: given a string such as "x", #"x" refers to the variable with that name (in this case, x).

For your program, you'd change dim(mat) to dim(#mat), and x→mat[i,j] to x→#mat[i,j]. Then to input the components of A, call readmat("A") (the argument should be a string, since it refers to the name of the variable).

Re: help with program please

pipapowerpongo 17 Jun 2009 21:25

it works!!!!!!!
thanks a lot

but isnt there another more elegant way by returning a value of a funktion, i mean by entering into a program with some varialble "prog(variable), doing something with it and giving that variable another value

like thist you have to remember that you have to put in a string so enter with ""

Re: help with program please

DarkerLine 17 Jun 2009 22:02

Unfortunately, there isn't a better way. If you used a function, you could return a variable, but that isn't quite the same thing, and you can't use Input in a function anyway.

Re: help with program please

pipapowerpongo 17 Jun 2009 22:03

i guess my question is not really clear
here the codes

readmat(mat)
Prgm
ClrIO
Local d,k,l,i,j,x
dim(#mat)->d
d[1]->k
d[2]->l
Disp k,l
For i,1,k,1
  ClrIO
  For j,1,l,1
    Disp "a"&string(i)&","&string(j)&"="
    Input x
    x->#mat[i,j]
    EndFor
EndFor

matradd()
Prgm
ClrIO
Disp "1. matrix"
Prompt mat1
readmat("mat1")
Disp "2. matrix"
Prompt mat2
readmat("mat2")
Disp mat1,mat2
Disp "+","="
Disp mat1+mat2
Disp
EndPrgm
EndPrgm

in home i define 2 matrixes 2x2 and name them q and w
then i call matradd
and it works, so it shows the two new matrixes q and w and the addition of theese both matrixes
but in home q and w are still the same then before
so if i wanna use the program readmat as a subprogramm in another programm it doesnt do what i wannt it to

i hope this make my question a bit clearer a bit clearer now

Re: help with program please

DarkerLine 17 Jun 2009 23:00

Okay here is what is going on.

When the calculator reaches Prompt mat1 in the code, it asks you for a value to store to the variable mat1. You enter q, so it takes the value of the matrix q, and stores it to a new matrix called mat1. Then readmat("mat1"), due to the indirection tricks we used, inputs values to store into mat1. The matrix q never gets modified.

If you want to modify a variable outside the program, you'll need the name of the variable, as opposed to the value of the variable, and Prompt won't help you with that. You want to read a string (variable names are strings), so use InputStr. In this case, you'd replace Prompt mat1 with InputStr name1. I use a variable called name1 to emphasize that we're not dealing with a matrix here, but the name of a matrix variable.

Then, since we already have a variable name, we can call readmat(name1) with no additional quotes necessary. If you run this program and enter q when prompted, name1 will be equal to "q", and readmat(name1) will be readmat("q"), and read entries into the variable q.

As for the rest of matradd(): change the part for the second matrix in the same way. For the last part, to get at the values of the matrices whose names we have, we'll need to use # again:

Disp #name1, #name2
Disp "+", "="
Disp #name1+#name2

If you ever end up learning a real programming language (such as C) you'll learn about pointers. With the # command, variable names are like pointers in TI-Basic, except real pointers use memory addresses instead. Probably best not to worry about this too much for now.

Last edited on 17 Jun 2009 23:00 by DarkerLine Show more

Re: help with program please

pipapowerpongo 17 Jun 2009 23:27

thanks a lot thats what i was looking for

i know a bit of c++, and was looing for pointers but couldnt find any similar in tibasic

is there anywhere a place in the forum where everybody puts on his programms for everybody, i guess thats the best way to learn it!

i still got 1 question: what do u think about writing in c, compiling on computer and then sending it to the calculator? is that a better way, or just more complicated?

thanks again

Re: help with program please

DarkerLine 17 Jun 2009 23:46

It depends on what you're doing. Math programs are probably best written in TI-Basic (a C program compiled with TIGCC will use the same routines anyway, so it won't be any faster, but it will be more annoying to write). Anything else, C is fairly good for, and some people prefer writing programs on the computer anyway.

Re: help with program please

rhombus p 18 Jun 2009 12:14

couldn't you write it in C and then compile it to asm? that would be faster.

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Re: help with program please

DarkerLine 18 Jun 2009 15:06

That is in fact what we're talking about here.

Re: help with program please

rhombus p 18 Jun 2009 15:13

oh, woops

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