Disclosed is a method and apparatus for matching regular expressions. A buffer of symbols giving a number of the last occurrence positions of each symbol is maintained. When two constants match on either side of a regular expression operator, the buffer of symbols is queried to determine if a member of the complement of the regular expression operator occurred between the two constants. If so, then the operator was not satisfied. If not, then the operator was satisfied.
Please help me write a proper abstract based on the patent claims. CLAIM: 1. A system that matches a string of symbols to a regular expression pattern, said regular expression pattern comprising a first constant, a second constant, and a first operator, said first operator occurring between said first constant and said second constant in said regular expression pattern, comprising: a deterministic finite automaton (DFA) engine that matches said first constant to said regular expression pattern starting at a first position in said string of symbols, the first DFA engine matching said second constant to said regular expression pattern ending at a second position in said string of symbols; a buffer of symbols that associates a plurality of positions of occurrences of a plurality of symbols in said string of symbols, said buffer of symbols producing an indicator that a position of a symbol from a complementary set of symbols is between said first position and said second position, said complementary set of symbols being based on a complement of said first operator, said indicator corresponding to whether the first operator is satisfied. 2. The system of claim 1, wherein said buffer of symbols selects an occurrence position from said plurality of positions of occurrences based on associations to said complementary set of symbols. 3. The system of claim 1, further comprising: a plurality of that match a plurality of constants to said regular expression pattern at a plurality of starting positions and a plurality of ending positions in said string of symbols, said plurality of starting positions and said plurality of ending positions defining a plurality of ranges of positions that are compared with at least one of said positions of occurrences to determine if at least one of a plurality of operators occurring between two of said plurality of constants is not satisfied. 4. A method of matching a string of symbols to a regular expression pattern, said regular expression pattern comprising a first constant, a second constant, and a first operator, said first operator occurring between said first constant and said second constant in said regular expression pattern, comprising: using a first deterministic finite automaton (DFA), matching said first constant to said regular expression starting at a first position in said string of symbols and matching said second constant to said regular expression ending at a second position in said string of symbols; and, associating a plurality of positions of occurrences of a plurality of symbols in said string of symbols; producing an indicator that a position of a symbol from a complementary set of symbols is between said first position and said second position, said complementary set of symbols being based on a complement of said first operator, said indicator corresponding to whether the first operator is satisfied. 5. The method of claim 4, further comprising: selecting an occurrence position from said plurality of positions of occurrences based on associations to said complementary set of symbols. 6. The method of claim 4, further comprising: matching a plurality of constants to said regular expression pattern at a plurality of starting positions and a plurality of ending positions in said string of symbols, said plurality of starting positions and said plurality of ending positions defining a plurality of ranges of positions that are compared with at least one of said positions of occurrences to determine if at least one of a plurality of operators occurring between two of said plurality of constants is not satisfied. 7. A computer readable medium having instructions stored thereon for matching a string of symbols to a regular expression pattern, said regular expression pattern comprising a first constant, a second constant, and a first operator, said first operator occurring between said first constant and said second constant in said regular expression pattern that, when executed by a computer, at least instruct the computer to: using a first deterministic finite automaton (DFA), match said first constant to said regular expression starting at a first position in said string of symbols and match said second constant to said regular expression ending at a second position in said string of symbols; and, associate a plurality of positions of occurrences of a plurality of symbols in said string of symbols; and, produce an indicator that a position of a symbol from a complementary set of symbols is between said first position and said second position, said complementary set of symbols being based on a complement of said first operator, said indicator corresponding to whether the first operator is satisfied. 8. The computer readable medium of claim 7, wherein the computer is further instructed to: select an occurrence position from said plurality of positions of occurrences based on associations to said complementary set of symbols. 9. The computer readable medium of claim 7, wherein the computer is further instructed to: match a plurality of constants to said regular expression pattern at a plurality of starting positions and a plurality of ending positions in said string of symbols, said plurality of starting positions and said plurality of ending positions defining a plurality of ranges of positions that are compared with at least one of said positions of occurrences to determine if at least one of a plurality of operators occurring between two of said plurality of constants is not satisfied.