Ok, maybe this example will prove why it's not happening correctly: program Const_Vs_Var;
Const A_const = Integer(8427); B_const = Byte(33); C_const = Single(1440.5); Win_Calc = 16854.045817424505380076362374176; Const_Ans = 16854.045817424505380076362374176 / (8427 + 33 / 1440.5); Var A_Var : Integer; B_Var : Byte; C_Var : Single; Const_Ans1, Var_Ans1 : Extended; Begin A_Var := A_Const; B_Var := B_Const; C_Var := C_Const; Var_Ans1 := Win_Calc / (A_Var+B_Var/C_Var); Const_Ans1 := Win_Calc / (A_Const+B_Const/C_Const); WRITELN ( ' Const_Ans = ', Const_Ans:20:20); WRITELN ( ' Const_Ans1 = ', Const_Ans1:20:20); WRITELN ( ' Var_Ans1 = ', Var_Ans1:20:20); End. The result is: Const_Ans = 2.00000010627116630224 Const_Ans1 = 2.00000010627116630224 Var_Ans1 = 2.00000000000000000000 Now you can see, if the math was done the same as the way math is done for variables, we could have stored the constants as Byte(2). But because the math is being carried out after the reduction in precision we are left with storing this as extended. If the result of all the math can be reduced, or if there is no math, then it's great to reduce precision, but if the reduction in precision happens before the math, you can end up with the opposite of what you intended. Sure the compiler is working with faster math, but who cares what the compiler has to do, now we're going to be stuck with a program using extended(2.00000010627116630224) for any calculations that use Const_Ans instead of byte(2); if Const_Ans is used in some kind of iterative process, it the program could be using this extended millions of times when it could have been using a byte. Notice when I do the EXACT same math with variables, it DOES give me a result of 2, and THAT can be reduced. If the answer after all the math can be reduced, it should be reduced, if it can't be, then it should not be. Math with constants should be the same as math with variables. I'm trying to show there doesn't need to be a trade off at all, the math with constants just needs to be done correctly... as in the exact same way math with variables is done. What has happened is the math with constants was written and tested with the assumption that all constants would be full precision, because it was impossible for constants to be anything other than full precision, but now that is no longer the case and the math with constants isn't working correctly anymore. Either the math needs to happen before the reduction in precision or the math needs to be fixed so it works the same as math with variables, either way there won't need to be a trade off and everything will work the way everyone wants it to.. performance when possible and precision when needed. James _______________________________________________ fpc-pascal maillist - fpc-pascal@lists.freepascal.org https://lists.freepascal.org/cgi-bin/mailman/listinfo/fpc-pascal
