[Math] How to create an array in TI-89 Titanium calculator

calculator

Has anyone experienced using TI-89 BASIC programming to solve math problems? I want to create an array using TI-89 but I don't know how?

Update
I tried both

{0, 0, 0, 0}->A

and

[0, 0, 0, 0]->A

Basically, I want to create a boolean array to check for duplicate digits of a number.

Update 1

dup(n)
Prgm
    {0,0,0,0,0,0,0,0,0,0}->a
    1->d // digit
    While n > 0
        mod(10,n)->d
        If a[d] = 0 Then 1->a[d]
        Else Return 1
        EndIf
        floor(n/10)->n
    EndWhile    
    Return 0
EndPrgm

Thanks,
Chan

Best Answer

I don't have an 89 at hand to check, but I suspect that you can use lists (contained in {}, comma-separated) in much the same way you'd use an array, including subscript-based accessing.

As it turns out, I do have a TI Voyage 200, which is functionally identical to a TI-89 Titanium (runs the same OS, but more memory, better screen, QWERTY keyboard). I am able to store a list into a variable:

{2,4,6,8}->a (where -> is the "sto>" key)

and access items in that list:

a[3] is reformatted as $a_3$ and returns 6.

In what way was {0, 0, 0, 0}->A not working for you?

Okay, here are some relatively messy thoughts, but hopefully some of it will be helpful. You can create a list of the digits in a number n with

seq(mod(floor(n/10^k),10),k,0,floor(log(n)))->digitList

(the ones digit will be the first item in the list, ...)

Now, having a list of the digits, you can sort the list using

SortA digitList

Construct a list of the differences between successive terms of digitList (where there will be 0s for duplicated digits):

∆List(digitList)->deltaList

Now, you can do something like looping over deltaList and whenever you find a zero, check the corresponding location in digitList to see which digit is repeated.

Alternately, you could step through the sorted digitList, tracking the previous entry, and find duplicates that way.

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