From: jrs@merlyn.demon.co.uk   
      
   JRS:  In article <19cik154cckref8e9duduins86dghajpbi@4ax.com>, dated   
   Sun, 9 Oct 2005 17:07:15, seen in news:comp.lang.pascal.borland, Bart   
    posted :   
   >   
   >Using a faster hashfunction:   
   >   
   >function CodonHash(const ACodon: tCodon): Longint;   
   >begin   
   >  Result := (Ord(ACodon[1]) shl 16) + (Ord(ACodon[2]) shl 8) +   
   >Ord(ACodon[3]);   
   >end;   
      
   Although that's like a Hash, you're not really using it as one.   
      
   It looks like Delphi; I don't recall Return in Pascal.  This should be   
   quicker, and gives the same but with a leading 3.   
      
           function CodonHash(const ACodon: tCodon): Longint;   
           begin CodonHash := Longint(ACodon) end;   
      
   Since it's so simple, don't use a function.   
      
   Or, since the codons are made of ACGU only, encode each letter as 2 bits   
   and store in a byte; you can then look the translation up in a small   
   array of enumerated or string (fill unused entries with 0 or '').   
      
   Since a letter needs only 5 bits, you could try encoding three in a byte   
   as (X1*2+X2)*2+X3; there *may* be no duplicates.  In fact, only 3 bits   
   vary in ACGU : ...X.XX. : so (X1*32+X2)*32+X3 looks safe, using word   
   arithmetic.   
      
   Remember that Pascal is 16-bit, so using a longint is a 2-step process,   
   unlike in 32-bit Delphi.   
      
   Arrange your numbers in order, and use a binary search; for 64 entries,   
   that's about 6 comparisons rather than average 32.   
      
   For elegance, use an enumerated type whenever it suits.   
      
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