From boost-1.30.2 I built the list_parser.cpp example using MSVC++7.1. In the CSV list I added ",,2" to the end of the line to be parsed. The program ran but the neither of the added elements were included in the output vector. Having used the tokenizer before I know it will generally gobble up adjacent delimiters without any output. You can get the empty token if you ask for the delimiters as well and then just discard the delimiters (sort of). But I was surprised that the 2 didn't make it to the output vector. I expected the empty list entry would not make the output vector. I tried adding ~anychar_p to the rule but that didn't help. If I change the input list to add ",\"\",2" I get "" and 2 in the output vector. Applications like spreadsheets do not put missing column values for numeric columns as "" items generally. Maybe I am missing something because it certainly isn't the behavior I would expect (either from the parser or the tokenizer).