Edit report at https://bugs.php.net/bug.php?id=39280&edit=1
ID: 39280
Updated by: ni...@php.net
Reported by: arendjr at gmail dot com
Summary: Support for lazy evaluation type
-Status: Open
+Status: Closed
Type: Feature/Change Request
-Package: Feature/Change Request
+Package: *General Issues
Operating System: All
PHP Version: 5.1.6
-Assigned To:
+Assigned To: nikic
Block user comment: N
Private report: N
New Comment:
Closing as closures are supported as of PHP 5.3 and they can be used to lazily
evaluate code.
Previous Comments:
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[2006-10-27 15:12:59] arendjr at gmail dot com
Description:
------------
This is a feature request for a special language feature in PHP. I'm not sure
how hard this feature would be to implement, but given the scripting nature of
PHP I can imagine it not being too hard and it would be very useful if PHP6
could support this.
What I want to ask for is a new variable type that would support lazy
evaluation. I'm not sure what would be a suitable syntax for such a feature,
but let's assume for a moment it would use sqaure brackets.
This feature would allow someone to write code like:
$foo = [1+1];
This statement would basically store the string "1+1" in $foo, and $foo would
be marked as being of type "lazy". Only when at some point the value of $foo
is being read, the code will be evaluated and the real result will be stored
in $foo. So, if someone would subsequently execute the following statement:
echo $foo;
This would actually expand to:
$foo = eval("return (1+1);");
echo $foo;
This feature would make it very easy to write code that would conditionally
avoid potentially expensive statements.
As an example, imagine a case where you have to call some function bar() that
takes an argument from which you do not know in advance whether the function
will actually use the argument because whether the argument is used depends on
some external factor. However, calculating the argument may be a very CPU
intensive task. In this case you could write:
bar([someVeryExpensiveFunction()]);
Thus avoiding the execution of someVeryExpensiveFunction() in the case bar()
does not actually use its value.
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Edit this bug report at https://bugs.php.net/bug.php?id=39280&edit=1
