Re: [fpc-pascal] Bit manipulation helpers
W dniu 2022-02-21 o 13:34, gabor via fpc-pascal pisze: W dniu 2022-02-21 o 13:18, Ryan Joseph via fpc-pascal pisze: Oh my, I was confusing my terms I think. I wanted to do bit masking (I think it's called). I was expecting there to be something like TestFlag in the RTL since I can never remember the syntax "Value = (Value or Index)" function TestFlag(Value: QWord; Index: Byte): Boolean; begin result := Value = (Value or Index); end; Should you use the "AND" operator instead of "OR" for bit testing? result := Value = (Value AND Index); Of course not. My mistake. Michał. ___ fpc-pascal maillist - fpc-pascal@lists.freepascal.org https://lists.freepascal.org/cgi-bin/mailman/listinfo/fpc-pascal
Re: [fpc-pascal] Bit manipulation helpers
On Mon, 21 Feb 2022 13:34:29 +0100 gabor via fpc-pascal wrote: > W dniu 2022-02-21 o 13:18, Ryan Joseph via fpc-pascal pisze: > > Oh my, I was confusing my terms I think. I wanted to do bit masking > > (I think it's called). I was expecting there to be something like > > TestFlag in the RTL since I can never remember the syntax "Value = > > (Value or Index)" function TestFlag(Value: QWord; Index: Byte): > > Boolean; begin result := Value = (Value or Index); > > end; > > Should you use the "AND" operator instead of "OR" for bit testing? > > result := Value = (Value AND Index); No. result := (Byte(Value) AND Index)>0; result := Index = (Byte(Value) AND Index); result := Byte(Value) = (Byte(Value) OR Index); Mattias ___ fpc-pascal maillist - fpc-pascal@lists.freepascal.org https://lists.freepascal.org/cgi-bin/mailman/listinfo/fpc-pascal
Re: [fpc-pascal] Bit manipulation helpers
> On Feb 21, 2022, at 7:31 PM, Michael Van Canneyt via fpc-pascal > wrote: > > Hm. I'm not sure that this code does what you need. > > But masking is indeed not in the helpers. > Try it yourself, it does indeed work. How else are you supposed to test these kinds of bit flag APIs where all the flags are OR'd together into an LongWord? A type helper would be great because clearly this stuff is hard to remember. Regards, Ryan Joseph ___ fpc-pascal maillist - fpc-pascal@lists.freepascal.org https://lists.freepascal.org/cgi-bin/mailman/listinfo/fpc-pascal
Re: [fpc-pascal] Bit manipulation helpers
W dniu 2022-02-21 o 13:18, Ryan Joseph via fpc-pascal pisze: Oh my, I was confusing my terms I think. I wanted to do bit masking (I think it's called). I was expecting there to be something like TestFlag in the RTL since I can never remember the syntax "Value = (Value or Index)" function TestFlag(Value: QWord; Index: Byte): Boolean; begin result := Value = (Value or Index); end; Should you use the "AND" operator instead of "OR" for bit testing? result := Value = (Value AND Index); Michał. ___ fpc-pascal maillist - fpc-pascal@lists.freepascal.org https://lists.freepascal.org/cgi-bin/mailman/listinfo/fpc-pascal
Re: [fpc-pascal] Bit manipulation helpers
On Mon, 21 Feb 2022, Ryan Joseph via fpc-pascal wrote: On Feb 21, 2022, at 7:01 PM, Michael Van Canneyt via fpc-pascal wrote: Yes, this is testbit. Why do you say it does not work ? Oh my, I was confusing my terms I think. I wanted to do bit masking (I think it's called). I was expecting there to be something like TestFlag in the RTL since I can never remember the syntax "Value = (Value or Index)" function TestFlag(Value: QWord; Index: Byte): Boolean; begin result := Value = (Value or Index); end; Hm. I'm not sure that this code does what you need. But masking is indeed not in the helpers. Michael. ___ fpc-pascal maillist - fpc-pascal@lists.freepascal.org https://lists.freepascal.org/cgi-bin/mailman/listinfo/fpc-pascal
Re: [fpc-pascal] Bit manipulation helpers
> On Feb 21, 2022, at 7:01 PM, Michael Van Canneyt via fpc-pascal
> wrote:
>
> Yes, this is testbit.
>
> Why do you say it does not work ?
Oh my, I was confusing my terms I think. I wanted to do bit masking (I think
it's called). I was expecting there to be something like TestFlag in the RTL
since I can never remember the syntax "Value = (Value or Index)"
function TestFlag(Value: QWord; Index: Byte): Boolean;
begin
result := Value = (Value or Index);
end;
const
KMOD_LCTRL = $0040;
KMOD_RCTRL = $0080;
var
flags: LongWord;
begin
flags := KMOD_LCTRL + KMOD_RCTRL;
writeln('TestBit: ', flags.TestBit(KMOD_LCTRL));
writeln('TestFlag: ', TestFlag(flags, KMOD_LCTRL));
Regards,
Ryan Joseph
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Re: [fpc-pascal] Bit manipulation helpers
On Mon, 21 Feb 2022, Ryan Joseph via fpc-pascal wrote: I tried to use the bit helpers like https://www.freepascal.org/docs-html/rtl/sysutils/twordhelper.testbit.html but the bit to test is 0..15. There are only 16 bits in a word, so that is correct. I expected this to work like https://wiki.freepascal.org/Bit_manipulation but that doesn't seem to be the case. Does there exist bit helpers like GetBit (from the last link) in the RTL? Yes, this is testbit. Why do you say it does not work ? Michael. ___ fpc-pascal maillist - fpc-pascal@lists.freepascal.org https://lists.freepascal.org/cgi-bin/mailman/listinfo/fpc-pascal
[fpc-pascal] Bit manipulation helpers
I tried to use the bit helpers like https://www.freepascal.org/docs-html/rtl/sysutils/twordhelper.testbit.html but the bit to test is 0..15. I expected this to work like https://wiki.freepascal.org/Bit_manipulation but that doesn't seem to be the case. Does there exist bit helpers like GetBit (from the last link) in the RTL? Regards, Ryan Joseph ___ fpc-pascal maillist - fpc-pascal@lists.freepascal.org https://lists.freepascal.org/cgi-bin/mailman/listinfo/fpc-pascal
