Re^4: Practical Example of Converting Packed Value

Yeah, BrowserUk was adding that last bit while I was too hastily replying to his very helpful post.

I understand the bitmask and the right-shift operations much better now. This example had the concreteness and immediacy I needed. It helps me a lot to display the bitmask AND operation in binary.

my $day   = ( $short_int & 0b0000000_0000_11111 )      ;
my $month = ( $short_int & 0b0000000_1111_00000 ) >> 5 ;
my $year  = ( $short_int & 0b1111111_0000_00000 ) >> 9 ;

my $date  = sprintf "%04d-%02d-%02d", 1980 + $year, $month, $day;
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Is there any reason not to use these binary constants instead of hexadecimal constants in the real program?

I suppose in a real program, the binary/hexadecimal constants and the year 1980 would be symbolic constants; e.g., DAY_MASK and EPOCH_YEAR. Or not.

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Re^5: Practical Example of Converting Packed Value by BrowserUk (Patriarch) on Dec 01, 2008 at 02:40 UTC
Is there any reason not to use these binary constants instead of hexadecimal constants in the real program? Absolutely not! I actually had to write the binary down and convert to derive the hex. Why did I do that? Simply, because I forgot that Perl can handle binary constants. Dumb, but true. I especially like your use of the benign underscore to clarify the breakdown++ Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error. "Science is about questioning the status quo. Questioning authority". In the absence of evidence, opinion is indistinguishable from prejudice. "Too many [] have been sedated by an oppressive environment of political correctness and risk aversion."	[reply]
Re^5: Practical Example of Converting Packed Value by ikegami (Patriarch) on Dec 01, 2008 at 04:00 UTC
Is there any reason not to use these binary constants instead of hexadecimal constants in the real program? One advantage of using hex/oct is that you can avoid having long, unreadable strings of bits in your code. The shortness of the masks and your use of "_" ~~invalidates~~ negates that advantage. It actually makes bin more readable. Another advantage of using hex/oct for masks is that it allows you to interpret data in hex/oct dumps more easily. Balance your need for readable raw data with your need for code readability and chose the one that suits you best. It's purely a judgment call. I suppose in a real program, the binary/hexadecimal constants and the year 1980 would be symbolic constants They're not going to change and their purpose is quite obvious based on the variable names. I don't think creating the seven symbolic constants would improve the code unless they are used in multiple locations.	[reply]