Identical blocks of code, I think make sense for copyright cases -- "they copied our code, look here it is lines 12 through 25". Instead I believe patents are about a particular implementation of an idea.
They are supposed to be about a particular implementation, but the USPTO awards then for ideas (stuff like "treat years less than 50 as 19xx and above 50 as 20xx" and LZW, which are each implementable in many ways).
Courts assume the USPTO is competent, so overturning a patent is extremely costly. The bottom line is: practically speaking, ideas are patentable but without complete certainty of prevailing in court.
Isn't one of the prerequisites of a patent also a 'new and novel idea'? Since the author did not base his work on the patent it is by definition not novel anymore. This is exacerbated by other implementations like libbruce (see other comments).
