One more form of magic quantity, though, is Employed in file formats. It truly is just a value incorporated as commonly the very first thing during the file which will help determine the file structure, the Model from the file format and/or even the endian-ness of The actual file.

Working with numbers in calculations apart from 0 or one that are not defined by some identifier or variable (which not merely can make the selection simple to alter in various areas by transforming it in a single spot, and also can make it clear into the reader just what the number is for).

You often see magic numbers embedded in file formats, mainly because documents could be despatched around alternatively promiscuously and eliminate any metadata about how they had been designed. Even so magic quantities may also be often used for in-memory details constructions, like ioctl() phone calls.

There is certainly more than one that means. The 1 given by most responses previously (an arbitrary unnamed variety) is actually a quite common a single, and the only thing I am going to say about that may be that many people head to the extreme of defining...

Let's place our lone "2" in the context of: padding := 2, exactly where the context can be a "GUI Container". On this context the meaning of two (as pixels or other graphical unit) features us A fast guess of its semantics (which means and intent).

Michael StumMichael Stum 180k119119 gold badges407407 silver badges538538 bronze badges five 29 Regardless of whether it may possibly't improve It is really continue to a foul plan mainly because it's not crystal clear what is going on on.

In case the default SMTP port for that application is modified, then it would need to become current in many locations producing the opportunity of inconsistency.

Numbers with a scale may have semantics too. For example, fake we have been producing copyright a D&D game, wherever we hold the notion of the monster.

Individuals at times acquire magic selection elimination further, by shifting these constants into separate documents to work as configuration. This is usually handy, but might also build more complexity than It is well worth.

What does goto reach? - Personal computer = target_address;. To me, these Unique magic quantities are merely disguised and indirect variations of the exact same issue - assignments that lead execution to a particular issue from the code - and as a result often noticably fewer readable and maintainable than basically utilizing crack.

Now my problem is: Is that this true? Or are there elements of the STL that cannot be implemented in pure C++ and want some "magic"/Unique compiler support?

This certainly comes about since python tries to open up magic file as dll, which is simple text. Immediately after incorporating .dll to filenames within the code i get the exact same magic.MagicException: could not come across any magic files!.

I believe static closing constants are overkill if you're using them in one approach. A closing variable declared at the best of the method is more readable IMHO.

C++0x requires it one move even further and delivers versions of these type attributes that really function correctly in all scenarios. And that could only be completed via some unspecified method of compiler guidance.