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abstract interpretation

資料來源 : Free On-Line Dictionary of Computing

abstract interpretation
     
         A partial execution of a program which gains
        information about its {semantics} (e.g. control structure,
        flow of information) without performing all the calculations.
        Abstract interpretation is typically used by compilers to
        analyse programs in order to decide whether certain
        optimisations or transformations are applicable.
     
        The objects manipulated by the program (typically values and
        functions) are represented by points in some {domain}.  Each
        abstract domain point represents some set of real
        ("{concrete}") values.
     
        For example, we may take the abstract points "+", "0" and "-"
        to represent positive, zero and negative numbers and then
        define an abstract version of the multiplication operator, *#,
        which operates on abstract values:
     
        	*# | + 0 -
        	---|------
        	+  | + 0 -
        	0  | 0 0 0
        	-  | - 0 +
     
        An interpretation is "safe" if the result of the abstract
        operation is a safe approximation to the abstraction of the
        concrete result.  The meaning of "a safe approximation"
        depends on how we are using the results of the analysis.
     
        If, in our example, we assume that smaller values are safer
        then the "safety condition" for our interpretation (#) is
     
        	a# *# b# <= (a * b)#
     
        where a# is the abstract version of a etc.
     
        In general an interpretation is characterised by the {domain}s
        used to represent the basic types and the abstract values it
        assigns to constants (where the constants of a language
        include primitive functions such as *).  The interpretation of
        constructed types (such as user defined functions, {sum type}s
        and {product type}s) and expressions can be derived
        systematically from these basic domains and values.
     
        A common use of {abstract interpretation} is {strictness
        analysis}.
     
        See also {standard interpretation}.
     
        (1994-11-08)
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