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Forum Index : Microcontroller and PC projects : PicoMite - left shift (<<) operator - bugy ?!!
| Author | Message | ||||
homa Guru  Joined: 05/11/2021 Location: GermanyPosts: 471 |
hello specialists, I need an evaluation here. Is the left shift (<<) function broken here? Or do I have a mistake in my thinking? I found this while trying to store the RFID bitstream from the Manchester code in a 64 bit integer. Look at the code and the output: PicoMite MMBasic Version 5.07.01 Copyright 2011-2021 Geoff Graham Copyright 2016-2021 Peter Mather > list ' test shift - bug ?!! Dim b=&hFFFFFFFFFFFFFFFF Print Bin$(b),b b=&b1 Print Bin$(b),b b=b<<1 Xor 1 Print Bin$(b),b b=b<<1 Xor 0 Print Bin$(b),b b=0 Print Bin$(b),b For i=1 To 65 b=b<<1 Xor 1 Print i, Bin$(b) Next i > run 1111111111111111111111111111111111111111111111111111111111111111 -1 1 1 11 3 110 6 0 0 1 1 2 11 3 111 4 1111 5 11111 6 111111 7 1111111 8 11111111 9 111111111 10 1111111111 11 11111111111 12 111111111111 13 1111111111111 14 11111111111111 15 111111111111111 16 1111111111111111 17 11111111111111111 18 111111111111111111 19 1111111111111111111 20 11111111111111111111 21 111111111111111111111 22 1111111111111111111111 23 11111111111111111111111 24 111111111111111111111111 25 1111111111111111111111111 26 11111111111111111111111111 27 111111111111111111111111111 28 1111111111111111111111111111 29 11111111111111111111111111111 30 111111111111111111111111111111 31 1111111111111111111111111111111 32 11111111111111111111111111111111 33 111111111111111111111111111111111 34 1111111111111111111111111111111111 35 11111111111111111111111111111111111 36 111111111111111111111111111111111111 37 1111111111111111111111111111111111111 38 11111111111111111111111111111111111111 39 111111111111111111111111111111111111111 40 1111111111111111111111111111111111111111 41 11111111111111111111111111111111111111111 42 111111111111111111111111111111111111111111 43 1111111111111111111111111111111111111111111 44 11111111111111111111111111111111111111111111 45 111111111111111111111111111111111111111111111 46 1111111111111111111111111111111111111111111111 47 11111111111111111111111111111111111111111111111 48 111111111111111111111111111111111111111111111111 49 1111111111111111111111111111111111111111111111111 50 11111111111111111111111111111111111111111111111111 51 111111111111111111111111111111111111111111111111111 52 1111111111111111111111111111111111111111111111111111 53 11111111111111111111111111111111111111111111111111111 54 1000000000000000000000000000000000000000000000000000000 55 10000000000000000000000000000000000000000000000000000000 56 100000000000000000000000000000000000000000000000000000000 57 1000000000000000000000000000000000000000000000000000000000 58 10000000000000000000000000000000000000000000000000000000000 59 100000000000000000000000000000000000000000000000000000000000 60 1000000000000000000000000000000000000000000000000000000000000 61 10000000000000000000000000000000000000000000000000000000000000 62 100000000000000000000000000000000000000000000000000000000000000 63 1000000000000000000000000000000000000000000000000000000000000000 64 1 65 11 > |
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TassyJim Guru Joined: 07/08/2011 Location: AustraliaPosts: 6283 |
Dim integer b You may also run into the sign bit causing odd results. Edited 2022-01-16 07:36 by TassyJim VK7JH MMedit |
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| homa Guru Joined: 05/11/2021 Location: GermanyPosts: 471 |
I don't think so, check the manual on page 21: BUT there the variable in the example is marked %, so I changed the test programme that way. See there! So I think it is not a direct error. The variable is by default a floating point number with no suffix. :-( What a guessing error. ESPECIALLY BECAUSE THE FIRST LINES WORKED! 64-bit Unsigned Integers MMBasic on the PicoMite supports 64-bit signed integers. This means that there are 63 bits for holding the number and one bit (the most significant bit) which is used to indicate the sign (positive or negative). However it is possible to use full 64-bit unsigned numbers as long as you do not do any arithmetic on the numbers. 64-bit unsigned numbers can be created using the &H, &O or &B prefixes to a number and these numbers can be stored in an integer variable. You then have a limited range of operations that you can perform on these. They are << (shift left), >> (shift right), AND (bitwise and), OR (bitwise or), XOR (bitwise exclusive or), INV (bitwise inversion), = (equal to) and <> (not equal to). Arithmetic operators such as division or addition may be confused by a 64-bit unsigned number and could return nonsense results. Note that shift right is a signed operation. This means that if the top bit is a one (a negative signed number) and you shift right then it will shift in ones to maintain the sign. To display 64-bit unsigned numbers you should use the HEX$(), OCT$() or BIN$() functions. For example, the following 64-bit unsigned operation will return the expected results: X% = &HFFFF0000FFFF0044 Y% = &H800FFFFFFFFFFFFF X% = X% AND Y% PRINT HEX$(X%, 16) Will display "800F0000FFFF0044" > list ' test shift - bug ?!! Dim b%=&hFFFFFFFFFFFFFFFF Print Bin$(b%),b% b%=&b1 Print Bin$(b%),b% b%=b%<<1 Xor 1 Print Bin$(b%),b% b%=b%<<1 Xor 0 Print Bin$(b%),b% b%=0 Print Bin$(b%),b% For i=1 To 65 b%=b%<<1 Xor 1 Print i, Bin$(b%) Next i > run 1111111111111111111111111111111111111111111111111111111111111111 -1 1 1 11 3 110 6 0 0 1 1 2 11 3 111 4 1111 5 11111 6 111111 7 1111111 8 11111111 9 111111111 10 1111111111 11 11111111111 12 111111111111 13 1111111111111 14 11111111111111 15 111111111111111 16 1111111111111111 17 11111111111111111 18 111111111111111111 19 1111111111111111111 20 11111111111111111111 21 111111111111111111111 22 1111111111111111111111 23 11111111111111111111111 24 111111111111111111111111 25 1111111111111111111111111 26 11111111111111111111111111 27 111111111111111111111111111 28 1111111111111111111111111111 29 11111111111111111111111111111 30 111111111111111111111111111111 31 1111111111111111111111111111111 32 11111111111111111111111111111111 33 111111111111111111111111111111111 34 1111111111111111111111111111111111 35 11111111111111111111111111111111111 36 111111111111111111111111111111111111 37 1111111111111111111111111111111111111 38 11111111111111111111111111111111111111 39 111111111111111111111111111111111111111 40 1111111111111111111111111111111111111111 41 11111111111111111111111111111111111111111 42 111111111111111111111111111111111111111111 43 1111111111111111111111111111111111111111111 44 11111111111111111111111111111111111111111111 45 111111111111111111111111111111111111111111111 46 1111111111111111111111111111111111111111111111 47 11111111111111111111111111111111111111111111111 48 111111111111111111111111111111111111111111111111 49 1111111111111111111111111111111111111111111111111 50 11111111111111111111111111111111111111111111111111 51 111111111111111111111111111111111111111111111111111 52 1111111111111111111111111111111111111111111111111111 53 11111111111111111111111111111111111111111111111111111 54 111111111111111111111111111111111111111111111111111111 55 1111111111111111111111111111111111111111111111111111111 56 11111111111111111111111111111111111111111111111111111111 57 111111111111111111111111111111111111111111111111111111111 58 1111111111111111111111111111111111111111111111111111111111 59 11111111111111111111111111111111111111111111111111111111111 60 111111111111111111111111111111111111111111111111111111111111 61 1111111111111111111111111111111111111111111111111111111111111 62 11111111111111111111111111111111111111111111111111111111111111 63 111111111111111111111111111111111111111111111111111111111111111 64 1111111111111111111111111111111111111111111111111111111111111111 65 1111111111111111111111111111111111111111111111111111111111111111 > Edited 2022-01-16 08:38 by homa |
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