Author Topic: Help with sub(  (Read 2560 times)

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Offline Scipi

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Help with sub(
« on: December 02, 2010, 08:27:07 pm »
I'm writing a small program in TI-BASIC to calculate derivatives, The way I have it so far is that when the final element inputed is to the 1st power, the result is written as x^0. Example: 5x^4+3x^1 would result in 20x^3+3x^0.

I'm trying to cut out that last bit but I keep getting an invalid dim error.

Here's the code I wrote to parse put that bit.
Code: [Select]
:sub(Str2,length(Str2)-2,length(Str2)->X
:if x="^0"
:sub(Str2,1,length(Str2)-2)->Str2

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Offline Yeong

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Re: Help with sub(
« Reply #1 on: December 02, 2010, 08:33:46 pm »
isn't last index is supposed to be 1 lower?
:sub(Str2,length(Str2)-2,length(Str2)-1->X
like this
I believe string value starts with 0.
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Offline FinaleTI

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Re: Help with sub(
« Reply #2 on: December 02, 2010, 08:34:33 pm »
I'm writing a small program in TI-BASIC to calculate derivatives, The way I have it so far is that when the final element inputed is to the 1st power, the result is written as x^0. Example: 5x^4+3x^1 would result in 20x^3+3x^0.

I'm trying to cut out that last bit but I keep getting an invalid dim error.

Here's the code I wrote to parse put that bit.
Code: [Select]
:sub(Str2,length(Str2)-2,length(Str2)->X
:if x="^0"
:sub(Str2,1,length(Str2)-2)->Str2

For one, you can't store a string to X or any real var, and two, that first sub string tries to copy a sub string from two spaces before the end of the string that is the length of the whole string.
sub() works like: sub(String,start position,length of sub string), not sub(String,start position,end position).

Try this code and see if it works:
Code: [Select]
sub(Str2,length(Str2)-1,2
If Ans="^0
sub(Str2,1,length(Str2)-2 -> Str2

Edit: To clarify this:
isn't last index is supposed to be 1 lower?
:sub(Str2,length(Str2)-2,length(Str2)-1->X
like this
I believe string value starts with 0.
It actually starts at 1.
« Last Edit: December 02, 2010, 08:36:23 pm by FinaleTI »


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Offline yunhua98

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Re: Help with sub(
« Reply #3 on: December 02, 2010, 08:36:36 pm »
first of all, you can't store a substring into a variable like "X", and second, when you have length(Str2)-2,length(Str2), that means however many tokens in Str2 minus two is the token you start from, but you want to go the length of Str2!  so you get Invalid Dim.

tl:dr:  syntax of Sub is "sub([string],[token # to start from],[# of tokens])"

EDIT:  super ninja'd  :P
« Last Edit: December 02, 2010, 08:37:00 pm by yunhua98 »

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Offline Yeong

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Re: Help with sub(
« Reply #4 on: December 02, 2010, 08:37:02 pm »
Oops. Ignore mine. I think I was confused with java.
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Offline Scipi

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Re: Help with sub(
« Reply #5 on: December 02, 2010, 08:47:59 pm »
Quote
EDIT:  super ninja'd

Try Uber ninja'd  :D I just got ninja'd three times over!

Thank you everyone. I just started working with the sub( function yesterday so I'm not too familiar with them.

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Wait... This just in, the Omnimagians have sent the UN a list of demands that must be met or else the world will be "submitted to the wrath of Netham45's Lobster Army". Such demands include >9001 crates of peanuts, sacrificial blue lobsters, and a wide assortment of cherry flavored items. With such computing power stored in the hands of such people, we can only hope these demands are met.

In the wake of these events, we can only ask, Why? Why do these people make these demands, what caused them to gather, and what are their future plans...

Offline jnesselr

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Re: Help with sub(
« Reply #6 on: December 02, 2010, 08:54:39 pm »
Quote
EDIT:  super ninja'd

Try Uber ninja'd  :D I just got ninja'd three times over!

Thank you everyone. I just started working with the sub( function yesterday so I'm not too familiar with them.
It's all good. Personally, I wish it could return null strings, and had that last item be the end index instead of length, but whatever.  I think it works well when used correctly.