Implicant
Boolean term that guarantees a function is true whenever the term is true
In Boolean logic, the term implicant has either a generic or a particular use. In the generic use, it refers to the hypothesis of an implication (implicant). In the particular use, a product term (i.e., a conjunction of literals) P is an implicant of a Boolean function F, denoted , if P implies F (i.e., whenever P takes the value 1 so does F).
For instance, implicants of the function
include the terms ,
,
,
,
as well as some others.
01Prime implicant
A prime implicant of a function is an implicant (in the above particular sense) that cannot be covered by a more general (more reduced, meaning with fewer literals) implicant. W. V. Quine defined a prime implicant to be an implicant that is minimal, that is, the removal of any literal from P results in a non-implicant for F. An essential prime implicant (also known as core prime implicant) is a prime implicant that covers an input combination, for which the function is true (i.e. outputs 1), that no combination of other prime implicants is able to cover.
Using the example above, one can easily see that while (and others) is a prime implicant,
and
are not. From the latter, multiple literals can be removed to make it prime:
,
and
can be removed, yielding
.
- Alternatively,
and
can be removed, yielding
.
- Finally,
and
can be removed, yielding
.
The process of removing literals from a Boolean term is called expanding the term. Expanding by one literal doubles the number of input combinations for which the term is true (in binary Boolean algebra). Using the example function above, we may expand to
or to
without changing the cover of
.
The sum of all prime implicants of a Boolean function is called its complete sum, minimal covering sum, or Blake canonical form.
Sources and credits
This article is adapted from the Wikipedia article “Implicant”, written by its contributors and licensed under CC BY-SA 4.0. Fathomly has changed the layout, removed citation markers, navigation and maintenance notices, and adjusted punctuation. This adapted version is shared under the same license. For references, see the original article.
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