How to iterate through an array, subtracting in BASIC

[+KayBee]

Hi Atarians,

 

I am self teaching BASIC and don't know where to go from here. If I have an array of 100 random integers, and I want to subtract each subscripted value from the one preceding it.

 

 

10 DIM X(100)

20 FOR A=1 TO 100

30 X(A)=INT(10*RND(1))+1

?

50 PRINT?

60 NEXT A

 

goal:

 

X(100)-X(99) print result

X(99)-x(98) print result

etc.

 

Any guidance would be appreciated. Thank you for your time.

KB

 

 

[Rybags]

100 FOR A=100 TO 2 STEP -1

110 ? X(A)-X(A-1)

120 NEXT A

 

You could just do the calculation inside the main loop but the first value wouldn't be calculatable since you need 2 elements defined before you can subtract.

Note arrays have element (0) so you could just DIM to 99 and use it.

[E474]

90 X(100)=INT(10*RND(1))+1

100 FOR A=99 TO 1 STEP -1

110 X(A)=INT(10*RND(1))+1

120 ? X(A+1)-X(A)

130 NEXT A

 

Or similar (no access to Basic at the moment)

[+KayBee]

Yup, got it now. Thank you gentlemen. And of course it seems obvious once you know the answer. Ahhh learning...

 

Cheers,

 

KB