Recently on another list a challenge was thrown down to solve the=

following using the quickest and shortest code. X-> X*2+1

This boils down in assembler to 2 lines. Someone then set about
seeing how their C compilers fared.

With FED C I noticed the difference in code length caused by just=
 a
simple change to the syntax.

There was only one compiler that managed a two line code however=
 the
professional version is quite expensive.

Code Follows.

//Program to solve X-> 2X +1

//shortest assembler version by Dmitriy A. Kiryashov
//comf    X,W
//subwf   X,W     ;or ,F
//*************************
//OR THIS
//
//set c
//rlf x,F


CDB 6/5/2002
unsigned char N=3D3;

void main()
{
  N=3D(N*2)+1;  // movfw N

             //  movwf ACC
             //  clrc
             //  rlf ACC
             //  incf  ACC
            //   movfw ACC

            //   movwf N
// 7 instructions
***********************************
 N=3D3;
   N*=3D2;  //   movlw 37
   N+=3D1;         //  movwf ACC
            //  clrf 14
            // call PushA
            // movwf FSR
            // movfw 0

            // movwf ACC
            //movlw 3
            //movwf ACC2
            // call MulUSA
            // call Pop2A
            //call SavePACC2A
            // incf  N
// 13 instructions plus the routine calls
}

Just thought this example proves it's worth playing with the code=
 to
get the best compilation.

Colin
--
cdb, cdb@barnard.name on 01/04/2002

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