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ville56
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Joined: 08/06/2022
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Posted: 12:58pm 17 Oct 2024

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I'm DIMing a float array with

DIM float xy(10)

OPTION BASE is not defined and thus is 0. I can access xy(0) to xy(10) which gives 11 elements. The manual says for DIM arrays the the NUMBER of elements is specified which would give xy(0) to xy(9). Why can i access the element xy(10) ....??? From my POV i should get an index out of bounds error. Btw, base and number of elements checked with BOUND ... no problems to see there.

Where did my thoughts thake the wrong exit?

Environment is WebMite, MMBasic 6.00.00RC8

Regards Gerald

73 de OE1HGA, Gerald

Mixtel90

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Posted: 01:36pm 17 Oct 2024

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The array bounds are only checked at runtime.
The DIM statement index is for the last element, not the number of elements including the zeroeth one. :)

If you use OPTION BASE 1 then you get an error if you attempt to reference x(0), but not if you use OPTION BASE 0.

AFAIK this is pretty normal behaviour in BASIC.
.
Edited 2024-10-17 23:38 by Mixtel90

Mick

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ville56
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Posted: 02:24pm 17 Oct 2024

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So this is an error in the manual as it says this is the number of elements not the index of the elements.

73 de OE1HGA, Gerald

Geoffg

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Posted: 02:38pm 17 Oct 2024

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Small point but OK, I will fix it.

Geoff

Geoff Graham - http://geoffg.net

Mixtel90

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Posted: 02:57pm 17 Oct 2024

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I don't think I've ever used OPTION BASE 1. I just check the boundaries if necessary. :) After all, if it goes out of bounds you're going to have to trap the error anyway or you'll leave the user with a crashed program, so why bother?

Mick

Zilog Inside! nascom.info for Nascom & Gemini
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Volhout
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Posted: 03:27pm 17 Oct 2024

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Mick,

Sometimes option base 1 is handy.

In the thermal camera there is a lot of vendor provided arrays an indexes in the documentation. These where in base 1 (in example the left most pixel in the array is (1,1) and not (0,0). Rather than continuously changing the pointer when transferring data from vendor array to arrays that can be processed with MATH statements (and getting confused), I used option base 1.

Also option base 1 in (this is standard in basic) strings. There is no left$(a$,0). The first character has index 1.

Volhout

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javavi

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Joined: 01/10/2023
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Posted: 03:42pm 17 Oct 2024

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In the LUA programming language, all array indices start with 1 only.

Mixtel90

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Posted: 03:54pm 17 Oct 2024

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I knew there was something putting me off LUA..... :)

If I want to use an array from 1 then I just ignore the zero element. I don't bother with OPTION BASE. I often DIM arrays slightly too big anyway. Sloppy, I know, but I'm rarely that stuck for RAM. :)

Mick

Zilog Inside! nascom.info for Nascom & Gemini
Preliminary MMBasic docs & my PCB designs

ville56
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Posted: 05:52pm 17 Oct 2024

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Thank you Geoff and sorry guys, i didn't want to start a discussion about base 0 or 1 ... ;-).
I'm just hunting a bug and I wanted to make sure I understand at least the language elements i'm using.

73 de OE1HGA, Gerald

toml_12953
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Posted: 12:07pm 18 Oct 2024

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Mixtel90 said The array bounds are only checked at runtime.
The DIM statement index is for the last element, not the number of elements including the zeroeth one. :)

If you use OPTION BASE 1 then you get an error if you attempt to reference x(0), but not if you use OPTION BASE 0.

AFAIK this is pretty normal behaviour in BASIC.
.

I believe he's saying that, when using OPTION BASE 0, you can still access array(10) which should flag an error. OPTION BASE 1 does work properly.

matherp
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Posted: 01:04pm 18 Oct 2024

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Quote I believe he's saying that, when using OPTION BASE 0, you can still access array(10) which should flag an error.

No it shouldn't

Quote The DIM statement index is for the last element, not the number of elements including the zeroeth one.

This correct

OPTION BASE 0 (default) creates an array from 0 to n where n is the dimension requested e.g. dim a(10) has elements 0-10. This is completely standard with most Basics and has been the way MMBasic works since its inception

stanleyella

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Posted: 04:59pm 18 Oct 2024

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dim sprite1(wh,bl,bl,bl,bl,bk,bk,bk,bk,bk,bk,bl,bl,bl,bl,wh,
bk,bl,re,re,re,bl,bl,bk,bk,bl,bl,re,re,re,bl,bk,
bk,bk,bk,bl,re,wh,bl,bk,bk,bl,wh,re,bl,bk,bk,bk,
bk,bk,bk,bl,re,wh,bl,bk,bk,bl,wh,re,bl,bk,bk,bk,
bk,bk,bk,bk,bl,wh,bl,bk,bk,bl,wh,bl,bk,bk,bk,bk,
bk,bk,bk,bk,bk,bl,bl,bk,bk,bl,bl,bk,bk,bk,bk,bk,
bk,bk,bk,bk,bk,bk,bk,bk,bk,bk,bk,bk,bk,bk,bk,bk,
bk,bk,bk,bk,ye,ye,ye,bk,bk,ye,ye,ye,bk,bk,bk,bk,
bk,bk,bk,ye,bk,bk,bk,bk,bk,bk,bk,bk,ye,bk,bk,bk,
bk,ye,ye,bk,bk,bk,bk,bk,bk,bk,bk,bk,bk,ye,ye,bk,
bk,ye,bk,bk,bk,bk,bk,bk,bk,bk,bk,bk,bk,bk,ye,bk,
ye,bk,bk,bk,bk,bk,bk,bk,bk,bk,bk,bk,bk,bk,bl,ye,
ye,bk,bk,bk,bk,bk,bk,bk,bk,bk,bk,bk,bk,bk,bk,ye,
ye,bk,bk,bk,bk,bk,bk,bk,bk,bk,bk,bk,bk,bk,bk,ye,
bk,ye,bk,bk,bk,bk,bk,bk,bk,bk,bk,bk,bk,bk,ye,bk,
bk,bk,ye,bk,bk,bk,bk,bk,bk,bk,bk,bk,bk,ye,bk,bk)

but get Error : Expected closing bracket
using mmedit ??
posted on another thread. regards, stan

matherp
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Posted: 05:02pm 18 Oct 2024

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Of course you do. MMbasic has never supported multi-line statements. You were shown how to do it with DATA statements

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