DEMORGAN'S THEOREM
\də mˈɔːɡənz θˈi͡əɹəm], \də mˈɔːɡənz θˈiəɹəm], \d_ə m_ˈɔː_ɡ_ə_n_z θ_ˈiə_ɹ_ə_m]\
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A logical theorem which states that the complementof a conjunction is the disjunction of the complements orvice versa. In symbols:not (x and y) = (not x) or (not y)not (x or y) = (not x) and (not y)E.g. if it is not the case that I am tall and thin then I ameither short or fat (or both). The theorem can be extended tocombinations of more than two terms in the obvious way.The same laws also apply to sets, replacing logical complementwith set complement, conjunction ("and") with setintersection, and disjunction ("or") with set union.A (C) programmer might use this to re-writeif (!foo && !bar) ...asif (! (foo || bar)) ...thus saving one operator application (though an optimisingcompiler should do the same, leaving the programmer free touse whichever form seemed clearest).
By Denis Howe
Word of the day
Dopamine Acetyltransferase
- An enzyme that catalyzes the of groups from acetyl-CoA to arylamines. They have wide specificity for aromatic amines, particularly serotonin, and can also catalyze acetyl transfer between arylamines without CoA. EC 2.3.1.5.