Abstract: The invention provides a pattern matching technique based on the symmetrical construction of the code structures representing the matching expression and the filter to be matched. The method of the invention is for determining whether a computer-storable expression matches a filter. A first code structure representing the expression is evaluated for determining a value of the expression. A second code structure representing the filter is analyzed for determining the characteristics of the filter. Then, the value is filtered according to the filter characteristics. The first code structure is constructed from a plurality of first programming language code structure elements and the second code structure is constructed from a plurality of second programming language code structure elements. Each second structure element corresponds to one of the first structure elements. This symmetrical construction of both code structures enables an arbitrary level of structural complexity.

Abstract: A statement evaluation technique is based on bi-evaluation of programming statements. A programming language statement is evaluated that includes a first and a second sub-statement. The first sub-statement is evaluated and an evaluation success result is determined if evaluation succeeds, or a distinguished value if evaluation fails. The distinguished value is a value that is not included in the range of possible evaluation success results of the first sub-statement. Further, it is determined whether the second sub-statement is to be evaluated. If this is the case, an evaluation success result of the second sub-statement is determined if evaluation succeeds, or the distinguished value if evaluation fails. The range of possible evaluation success results of the second sub-statement does not include the distinguished value. The evaluation result of the statement is determined depending on at least whether evaluation of the first sub-statement succeeds or fails.

Abstract: The invention provides a pattern matching technique based on the symmetrical construction of the code structures representing the matching expression and the filter to be matched. The method of the invention is for determining whether a computer-storable expression matches a filter. A first code structure representing the expression is evaluated for determining a value of the expression. A second code structure representing the filter is analyzed for determining the characteristics of the filter. Then, the value is filtered according to the filter characteristics. The first code structure is constructed from a plurality of first programming language code structure elements and the second code structure is constructed from a plurality of second programming language code structure elements. Each second structure element corresponds to one of the first structure elements. This symmetrical construction of both code structures enables an arbitrary level of structural complexity.

Abstract: A statement evaluation technique is based on bi-evaluation of programming statements. A programming language statement is evaluated that includes a first and a second sub-statement. The first sub-statement is evaluated and an evaluation success result is determined if evaluation succeeds, or a distinguished value if evaluation fails. The distinguished value is a value that is not included in the range of possible evaluation success results of the first sub-statement. Further, it is determined whether the second sub-statement is to be evaluated. If this is the case, an evaluation success result of the second sub-statement is determined if evaluation succeeds, or the distinguished value if evaluation fails. The range of possible evaluation success results of the second sub-statement does not include the distinguished value. The evaluation result of the statement is determined depending on at least whether evaluation of the first sub-statement succeeds or fails.