Search results
Results from the WOW.Com Content Network
Perl provides three loop control keywords that all accept an optional loop label as an argument. If no label is specified, the keywords act on the innermost loop. Within nested loops, the use of labels enables control to move from an inner loop to an outer one, or out of the outer loop altogether.
The empty hash {} is also true; in this context {} is not an empty block, because perl -e 'print ref {}' returns HASH. Evaluated boolean expressions are also scalar values. The documentation does not promise which particular value of true or false is returned. Many boolean operators return 1 for true and the empty-string for false.
Perl 5.6.1 and newer support autovivification of file and directory handles. [3] Calling open() on an undefined variable will set it to a filehandle. According to perl561delta, "[t]his largely eliminates the need for typeglobs when opening filehandles that must be passed around, as in the following example:
In comparison, Perl/Javascript, which also have the latter property, have other false-like values (0 and empty string), which make || differ from a null-coalescing operator in many more cases (numbers and strings being two of the most frequently used data types). This is what led Perl/Javascript to add a separate operator while Ruby hasn't.
The detailed semantics of "the" ternary operator as well as its syntax differs significantly from language to language. A top level distinction from one language to another is whether the expressions permit side effects (as in most procedural languages) and whether the language provides short-circuit evaluation semantics, whereby only the selected expression is evaluated (most standard ...
The Ruby programming language interpreter offers an eval function similar to Python or Perl, and also allows a scope, or binding, to be specified. Aside from specifying a function's binding, eval may also be used to evaluate an expression within a specific class definition binding or object instance binding, allowing classes to be extended with ...
Nullable types are a feature of some programming languages which allow a value to be set to the special value NULL instead of the usual possible values of the data type.In statically typed languages, a nullable type is an option type, [citation needed] while in dynamically typed languages (where values have types, but variables do not), equivalent behavior is provided by having a single null ...
By writing {{if empty|a|b|c}} instead of {{#if:a|a|{{#if:b|b|c}}}}, expression a and b do not have to be repeated and evaluated twice. The template provides a fallback order, similar to a try catch based "It is easier to ask for forgiveness than permission" ( EAFP ) programming style.