Editing Lazy evaluation (section)

===Other uses===
In computer [[windowing system]]s, the painting of information to the screen is driven by ''expose events'' which drive the display code at the last possible moment. By doing this, windowing systems avoid computing unnecessary display content updates.<ref name="Lampson">[http://research.microsoft.com/en-us/um/people/blampson/slides/lazyandspeculative.ppt Lazy and Speculative Execution] [[Butler Lampson]] [[Microsoft Research]] OPODIS, Bordeaux, France 12 December 2006</ref>

Another example of laziness in modern computer systems is [[copy-on-write]] page allocation or [[demand paging]], where memory is allocated only when a value stored in that memory is changed.<ref name="Lampson"/>

Laziness can be useful for high performance scenarios. An example is the Unix [[mmap]] function, which provides ''demand driven'' loading of pages from disk, so that only those pages actually touched are loaded into memory, and unneeded memory is not allocated.

[[MATLAB]] implements ''[[copy on write|copy on edit]]'', where arrays which are copied have their actual memory storage replicated only when their content is changed, possibly leading to an ''out of memory'' error when updating an element afterwards instead of during the copy operation.<ref>{{cite web|url=http://www.mathworks.co.uk/matlabcentral/answers/46551-out-of-memory-when-assigning-values-to-existing-arrays|title=Out of memory when assigning values to existing arrays? |work=MATLAB Answers |publisher=MATLAB Central}}</ref>