head normal form

from The Free On-line Dictionary of Computing (8 July 2008)

Head Normal Form

   <theory, reduction> (HNF) A term describing a {lambda
   expression} whose top level is either a variable, a data
   value, a built-in function applied to too few arguments, or a
   {lambda abstraction} whose body is not reducible.  I.e. the
   top level is neither a {redex} nor a lambda abstraction with a
   reducible body.

   An expression in HNF may contain redexes in argument postions
   whereas a {normal form} may not.

   Compare {Weak Head Normal Form}.

   (2003-01-08)