Partial function: Difference between revisions
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==References== | ==References== | ||
* {{cite book | author=Zohar Manna | title=Mathematical Theory of Computation | publisher=McGraw-Hill | year=1974 | isbn=0-07-039910-7 | pages=44 }} | * {{cite book | author=Zohar Manna | title=Mathematical Theory of Computation | publisher=McGraw-Hill | year=1974 | isbn=0-07-039910-7 | pages=44 }} | ||
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Revision as of 05:23, 27 February 2009
In mathematics and theoretical computer science, a partial function on a set is a function whose domain of definition need not be the whole set.
We may define a partial function f from X to Y by extending the codomain Y to Y* by an element ω for "undefined", assumed not to be in Y, so that f is a function in the usual sense from X to Y*, and we regard the domain of definition of f as the subset of X on which f does not take the value ω.
A function on X is total if its domain of definition is the whole of f: that is, if f is a function on X in the usual sense.
The set of partial functions from X to Y is partial order by extension: we say that f extends g if the domain of definition of f contains that of g and f agrees with g on the domain of g.
References
- Zohar Manna (1974). Mathematical Theory of Computation. McGraw-Hill, 44. ISBN 0-07-039910-7.