cannot infer argument types

[bioinfornatics]

Hi,

I have this error message ( i.e title ) and i do not see where i 
am wrong:


     this( in ubyte wordLength, in string sequence ){
         kMer = wordLength;
         bytePerChar = cast(ubyte)(T.sizeof / kMer);

         char[ubyte] toCharTmp;
         ubyte[char] toNumTmp;
         foreach( ubyte i, const char letter; 
sequence.dup.sort.uniq() ){
             if(i !in toCharTmp)
                 toCharTmp[ i ]  = letter;
             toNumTmp[ letter ]  = i;
         }
         toChar  = toCharTmp.rehash;
         toNum   = toNumTmp.rehash;
     }

Error is given at <foreach line>

I have removed explicit type on this line… but I have always same 
error!