In the context of computer programming, magic is an informal term for abstraction - it is used to describe code that handles complex tasks while hiding that complexity to present a simple interface. The term is somewhat tongue-in-cheek and carries good connotations, implying that the interface simplifies an otherwise difficult or tedious task. For example, Perl's polymorphic typing and closure mechanisms are often called "magic". The term implies that the hidden complexity is at least in principle understandable, in contrast to black magic and deep magic, which describe arcane techniques that are deliberately hidden or extremely difficult to understand.
Recent negative meaning
In recent years, however, a negative interpretation of the term has been gaining popularity. In this usage, "magic" refers to procedures which make calculations based on data not clearly provided to them, by accessing other modules, memory positions or global variables that they are not supposed to (in other words, they are not referentially transparent). According to most recent software architecture models, even when using structured programming, it is usually preferred to make each function behave the same way every time the same arguments are passed to it, therefore following one of the basic principles of functional programming. When a function breaks this rule, it is often said to contain "magic". A simplified example of negative magic is the following code in PHP:
function Magic() {
global $somevariable;
echo $somevariable;
}
$somevariable = true;
Magic();
While the code above is clear and maintainable, if it is seen in a large project, it is often hard to understand where the function Magic() gets its value from. It is preferred to write that code using the following concept:
function noMagic($myvariable) {
echo $myvariable;
}
$somevariable = true;
noMagic($somevariable);
See also
- Magic number (programming)
- Black magic (programming)
- Deep magic (programming)
- Voodoo programming
