hex to decimal conversion (Allgemeines zu Perl)

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hex to decimal conversion

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+13 replies
Gast thegreatonech

2010-06-10 15:05

Hallo,

I've got a hash. every key has a hexadecimal value with two signs like "fe" or "05" or "f4".
I have to put two of this hexs together to a hex with four signs like "fe05". (The first with the second, the third with the forth...)
coverted in decimal and multiplied with 10 i should get some temperatures.

my problem is: i can put the hexs together with "." and convert to decimal with "hex($hexvalue)". but they are not alway right! sometimes i've to put the lower value first ("feff") and sometimes i've to put the higher value first ("fffe") to get a logic result.

the hexs are out of a file. the description of the file means following:

The temperature value is a signed integer (two's complement, low - high representation) containing the temperature multiplied by decimal 10).

when I always take the lower value first I get some logic and some not logic temperatures. I guess I don't understand the "low - high representation" in the description.

i hope that someone can help me!

thank you[/code]
Last edited: 2010-06-10 15:07:15 +0200 (CEST)
- lichtkind
  
  2010-06-10 15:11
  
  User since
  2004-03-22
  5679 Artikel
  ModeratorIn + EditorIn
  
  See
  http://perldoc.perl.org/functions/hex.html
  Tutorien in der Wiki, mein zeug:
  kephra, baumhaus, garten, gezwitscher
  
  Es beginnt immer mit einer Entscheidung.
- +11 replies
- pq
  
  2010-06-10 15:13
  
  User since
  2003-08-04
  12208 Artikel
  Admin1
  
  hi, i'm answering in english, but if you speak german please continue in german then since this forum is a german speaking one.
  
  Guest thegreatonech
  I've got a hash. every key has a hexadecimal value with two signs like "fe" or "05" or "f4".
  
  so, this description tells me you have a hash with values like "fe" or "05".
  you don't mention the keys, so I assume that they don't matter.
  
  Quote
  I have to put two of this hexs together to a hex with four signs like "fe05". (The first with the second, the third with the forth...)
  
  problem at this point: you are talking about first, second and so forth. what is the first and the second? all we have until now is a hash. there is no order in a hash.
  what do you want to do? how is first and second defined? please give example input and output, so maybe we can at least guess from that.
  Always code as if the guy who ends up maintaining your code will be a violent psychopath who knows where you live. -- Damian Conway in "Perl Best Practices"
  lesen: Wie frage ich & perlintro brian's Leitfaden für jedes Perl-Problem
  - +10 replies
  - lichtkind
    
    2010-06-10 15:17
    
    User since
    2004-03-22
    5679 Artikel
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    plus: you consideren that in the right context 05 is interpreted as "5"which added the other hex number ist something completely different.
    Tutorien in der Wiki, mein zeug:
    kephra, baumhaus, garten, gezwitscher
    
    Es beginnt immer mit einer Entscheidung.
    - +9 replies
    - Gast thegreatonech
      
      2010-06-10 15:31
      
      thank you for your fast answers:
      
      @pq: (The first with the second, the third with the forth...) with this I mean the keys of the hash which are from 0 to 511. so i have to put key "0" with key "1" , key "2" with key "3" ...
      
      @plus: at the beginning the i'had single values like 5, put then I'putted a zero in front of them, so now I've every where "05" or "0d"
      
      Last edited: 2010-06-10 15:36:56 +0200 (CEST)
      - +6 replies
      - Gast thegreatonech
        
        2010-06-10 15:55
        
        maybe this can help:
        
        what i've got:
        
        a hash called %temp looking like this: (key and value) max.key =511
        0 58
        1 2
        2 51
        3 2
        4 49
        5 2
        6 42
        7 2
        8 3a
        9 2
        10 33
        11 2
        12 2b
        13 2
        14 24
        15 2
        16 1c
        17 2
        18 15
        19 2
        20 d
        21 2
        22 6
        23 2
        24 fe
        25 1
        26 f7
        .
        
        my code is following:
        
        Code: (dl )
        
        1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59
        
        for ($x=0; $x<=511; $x=$x+2){ $z=$x+1; if (hex($temp{$x}) > hex($temp{$z})){ $string1 = $temp{$z}; $length = length($string1); if ($length eq 1){ $string1 = "0".$string1; } $string2 = $temp{$x}; $length1 =length($string2); if ($length1 eq 1){ $string2 = "0".$string2; } $hexzahl = $string1.$string2; $deczahl = hex($hexzahl); $calibtemp{$y}= $deczahl; $calibtemp1{$y}= $hexzahl; } else{ $string1 = $temp{$z}; $length = length($string1); if ($length eq 1){ $string1 = "0".$string1; } $string2 = $temp{$x}; $length1 =length($string2); if ($length1 eq 1){ $string2 = "0".$string2; } $hexzahl = $string2.$string1; $deczahl = hex($hexzahl); $calibtemp{$y}= $deczahl; $calibtemp1{$y}= $hexzahl; } open (filename, ">>tempi.dat") or die "Fehler","\n"; print filename "$y"," ","$calibtemp{$y}","\n"; print filename "$y"," ","$calibtemp1{$y}","\n"; close (filename); $y++; }
        
        but the problem is that here i putted always the string with the lower value in front of the string with the higher value but thats not always right. I think it has to be a misunderstanding of the description I mentioned before.
        
        hope that can help
        Last edited: 2010-06-10 15:56:50 +0200 (CEST)
        
        +5 replies
        
        murphy
        
        2010-06-10 16:07
        
        User since
        2004-07-19
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        Guest thegreatonech
        [...]
        but the problem is that here i putted always the string with the lower value in front of the string with the higher value but thats not always right.
        [...]
        
        The description certainly doesn't mean that you have to sort the values before concatenating them. It's very likely that
        Quote
        low - high representation
        means the the low order digits are given first, followed by the high order digits.
        When C++ is your hammer, every problem looks like your thumb.
        
        +4 replies
        
        Gast thegreatonech
        
        2010-06-10 16:19
        
        Quote
        The description certainly doesn't mean that you have to sort the values before concatenating them. It's very likely that means the the low order digits are given first, followed by the high order digits.
        
        so you think I've to put the value of key "0" in front of the value of key "1"?
        I tried that but the results were without any logic!
        '5802' to decimal is 22530 multiplied by decimal 10 gives '2253' degree! but my values should be in the range of about +60 and -90 degrees.
        
        Last edited: 2010-06-10 16:23:13 +0200 (CEST)
        
        +3 replies
        
        murphy
        
        2010-06-10 16:28
        
        User since
        2004-07-19
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        If the low order digits come first, you have to put the value with index 0 after the one with index 1.
        When C++ is your hammer, every problem looks like your thumb.
        
        +2 replies
        
        Gast thegreatonech
        
        2010-06-10 16:41
        
        so I get the right value for this example!
        but unfortunately, there are other examples (not listed here) where I've to turn the indices to get the right value.
        
        I've to mention that the temperature decreases with the index (so index"0".index"1" is higher than index"50".index"51")
        
        i don't get the point.. i'm working the hole day on this! hmmm..
        Last edited: 2010-06-10 16:43:45 +0200 (CEST)
        
        murphy
        
        2010-06-10 16:47
        
        User since
        2004-07-19
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        Well, that's a pity. If the byte order of the data is really not fixed, that could also be a malfunction of your sensor or an error in the data transmission.
        When C++ is your hammer, every problem looks like your thumb.
      - +2 replies
      - murphy
        
        2010-06-10 16:01
        
        User since
        2004-07-19
        1776 Artikel
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        Guest thegreatonech
        [...]
        @pq: (The first with the second, the third with the forth...) with this I mean the keys of the hash which are from 0 to 511. so i have to put key "0" with key "1" , key "2" with key "3" ...
        [...]
        
        Why on earth do you store your data in a hash instead of an array if your keys are consecutive integers?
        
        Anyhow, you can do something like this:
        
        Code (perl): (dl )
        
        1 2 3 4 5 6 7 8 9 10 11 12
        
        use 5.012; my %hash = ( 0 => 'aa', 1 => 'bb', ... ); my $count = 512; my $_; for (0 .. ($count / 2)) { my $i = 2 * $_; say hex($hash{$i} . $hash{$i + 1}); }
        
        (code untested)
        When C++ is your hammer, every problem looks like your thumb.
        
        Gast thegreatonech
        
        2010-06-10 16:09
        
        @murphy:
        
        your right, an array would be better, i will change that.
        But that's not the problem! your code seems clear to me but makes the same mistake like mine! it's always the same order in putting the values together!($i in front of $i+1).

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