[1] : The Free On-line Dictionary of Computing (27 SEP 03)

lazy evaluation
     
         an evaluation strategy combining normal order
        evaluation with updating.  under normal order evaluation
        outermost or call-by-name evaluation an expression is
        evaluated only when its value is needed in order for the
        program to return the next part of its result.  updating
        means that if an expression's value is needed more than once
        i.e. it is shared, the result of the first evaluation is
        remembered and subsequent requests for it will return the
        remembered value immediately without further evaluation.  this
        is often implemented by graph reduction.  an unevaluated
        expression is represented as a closure - a data structure
        containing all the information required to evaluate the
        expression.
     
        lazy evaluation is one evaluation strategy used to implement
        non-strict functions.  function arguments may be infinite
        data structures especially lists of values, the components
        of which are evaluated as needed.
     
        according to phil wadler the term was invented by jim morris.
     
        opposite: eager evaluation.
     
        a partial kind of lazy evaluation implements lazy data
        structures or especially lazy lists where function arguments
        are passed evaluated but the arguments of data constructors
        are not evaluated.
     
        full laziness is a program transformation which aims to
        optimise lazy evaluation by ensuring that all subexpressions
        in a function body which do not depend on the function's
        arguments are only evaluated once.
     
        1994-12-14
     
     
see also:
evaluation strategy normal order evaluation closure strict eager evaluation lazy list 
full laziness program transformation 

Evaluation >> E Words
Evaluation, definition of term: Evaluation
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Lazy >> L Words
Lazy, definition of term: Lazy
lazy_pag1.html

Lazy Susan >> L Words
Lazy Susan, definition of term: Lazy Susan
lazy+susan_pag1.html