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Forum Index : Microcontroller and PC projects : CMM2: What is LONGSTRING RESIZE trying to do (bug?)
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thwill Guru  Joined: 16/09/2019 Location: United KingdomPosts: 4311 |
Found whilst writing unit-tests for Linux MMBasic: On the CMM2: > list "longstring_resize.bas" Option Base 0 Option Default None Option Explicit On Dim lstr%(100) Print "Should be 0, is" LLen(lstr%()) LongString Append lstr%(), "Hello World" Print "Should be 11, is" LLen(lstr%()) LongString Resize lstr%(), 4 Print "Should be 4 (?), is" LLen(lstr%()) > run "longstring_resize.bas" Should be 0, is 0 Should be 11, is 11 Should be 4 (?), is 5 Also note that the documentation for LONGSTRING RESIZE in the manual is incorrect as it is missing the array%() parameter, ditto LONGSTRING SETBYTE. Best wishes, Tom MMBasic for Linux, Game*Mite, CMM2 Welcome Tape, Creaky old text adventures |
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| matherp Guru Joined: 11/12/2012 Location: United KingdomPosts: 10310 |
This is the faulty line dest[0] = getint(argv[2],OptionBase,j-OptionBase)+1; should probably be dest[0] = getint(argv[2],OptionBase,j+OptionBase ); You might want to check the use of OptionBase throughout the longstring commands GetByte and SetByte are byte array index operations and should respect OptionByte Everything else are string operations where the first element is always one and OptionByte is irrelevant (except that it determines the size of the array and hence how many bytes are available) The bug is relatively benign and resize was really only there to allow setbyte on a newly created zero length longstring Edited 2021-09-06 02:29 by matherp |
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| thwill Guru Joined: 16/09/2019 Location: United KingdomPosts: 4311 |
Don't you mean: dest[0] = getint(argv[2], 0, j) ? As the minimum number of bytes/characters is always 0 and the maximum number is always 8 * (number of elements in the array - 1). Best wishes, Tom MMBasic for Linux, Game*Mite, CMM2 Welcome Tape, Creaky old text adventures |
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| matherp Guru Joined: 11/12/2012 Location: United KingdomPosts: 10310 |
this is the confusion of option base. I wish it didn't exist as it causes so much special case code. Does resize correspond to array indicies (e.g 1-8) or the number of slots (e.g 0-8)? Does 0 make sense? is it the same as clear? Edited 2021-09-06 17:15 by matherp |
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| thwill Guru Joined: 16/09/2019 Location: United KingdomPosts: 4311 |
You and me both. I hate it, and its partner in crime the "sizes" specified when arrays are declared being the maximum bound instead of the (sane to me) number of elements  .My opinion is that it is the number of byte/character elements and as a result any value that could be returned by LLEN should be a valid argument to LONGSTRING RESIZE hence 0 does make sense even though it is the same as LONGSTRING CLEAR ... otherwise the client code has to special case for 0 when it comes up as the result of a calculation. I would also argue that LONGSTRING TRIM should behave the same, currently it doesn't allow 1 and doesn't allow you to trim the entire string or beyond. I feel these "arbitrary" restrictions just make writing the client-code more difficult. However YMMV and I don't want the behaviour of MMBasic for Linux to differ as that just compounds the problem. Best wishes, Tom P.S. with the benefit of hindsight you could probably make an argument that LONGSTRING SETBYTE and LGETBYTE don't really belong in the language at all since we have POKE and PEEK. I guess there is a slight performance improvement. Edited 2021-09-06 18:44 by thwill MMBasic for Linux, Game*Mite, CMM2 Welcome Tape, Creaky old text adventures |
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jirsoft Guru Joined: 18/09/2020 Location: Czech RepublicPosts: 533 |
I find it not so bad for 2 reasons: 1. I don't need everytime in the loop calculate size-1 as TO limit. (You haven't this problem in C as the upper for for loop is not reachable) 2. I'm programming with OPTION BASE 0, but sometimes not using first element (0), so I have this way eliminated MMBasic's problem with one element array... Jiri Napoleon Commander and SimplEd for CMM2 (GitHub), CMM2.fun |
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| matherp Guru Joined: 11/12/2012 Location: United KingdomPosts: 10310 |
Tom Change your code to dest[0] = getint(argv[2], 0, j) I'll do the same if/when there is another CMM2 release |
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| thwill Guru Joined: 16/09/2019 Location: United KingdomPosts: 4311 |
Than you Peter, I will do so. Best wishes, Tom MMBasic for Linux, Game*Mite, CMM2 Welcome Tape, Creaky old text adventures |
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