principal type

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principal type

The most general type of an expression. For example, the following are all valid types for the lambda abstraction (\ x . x):

Int -> Int Bool -> Bool (a->b) -> (a->b)

but any valid type will be an instance of the principal type: a -> a. An instance is derived by substituting the same type expression for all occurences of some type variable. The principal type of an expression can be computed from those of its subexpressions by Robinson's unification algorithm.
This article is provided by FOLDOC - Free Online Dictionary of Computing (
References in periodicals archive ?
Ethanol is, according to online encyclopedia Wikipedia, a "simple alcohol, the principal type of alcohol found in alcoholic drinks.
The principal type of stomata are polycytic but differs in being 10% diacytic and 10% anomocytic.
MANOVA found significant differences in attachment style by Principal Type and Age Group.
The expected fitness for principal type [P.sub.1] is [MATHEMATICAL EXPRESSION NOT REPRODUCIBLE IN ASCII], and for [P.sub.2], it is [MATHEMATICAL EXPRESSION NOT REPRODUCIBLE IN ASCII].
Tax Withheld, and U.S.-Source Income, by Principal Type of Income, Selected Recipient Type, and Selected Country of Recipient, 2008 [Money amounts are in thousands of dollars] Selected country or Number U.S.
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In the other principal type of regio errors, the insertion of the propylene occurs by a 1,3 insertion such that the section of the chain contains only incorporated methylene units.
The nature of the principal type 1 interferon-producing cells in human blood.
While credit cards remain the principal type of electronic payment in the United States in terms of the number and share of transactions, the use of debit cards is growing at a much faster rate.
Eighteen-Degree Water was first described by WHOI physical oceanographer Valentine Worthington in 1959 as one of the major water masses formed in the northern Sargasso Sea in late winter: It is the principal type of subtropical water found in the North Atlantic.
(6.) In 1992, approximately 49 percent of those who used section 203Co) FHA loans (the principal type of FHA single-family loan program) were first-time homebuyers.

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