The only markdown implementation I know of, that uses an actual parser, is Jon MacFarleane’s peg-markdown. Its parser is based on a Parsing Expression Grammar parser generator called peg. EDIT: Mauricio Fernandez recently released his Simple Markup Markdown parser, which he wrote as part of his OcsiBlog Weblog Engine. Because the parser is written in … Read more
There are some differences between Lex and Flex, but you have to be abusing Lex to run into the problems with Flex. (I have a program which abuses Lex and doesn’t work under Flex, therefore.) This is primarily in the area of input lookahead; in Lex, you can provide your own input code and modify … Read more
I think the verb you want is ‘compose’.
I saw this question a lot when I worked for an address verification company. I’m posting the answer here to make it more accessible to programmers who are searching around with the same question. The company I was at processed billions of addresses, and we learned a lot in the process. First, we need to … Read more
A tokenizer breaks a stream of text into tokens, usually by looking for whitespace (tabs, spaces, new lines). A lexer is basically a tokenizer, but it usually attaches extra context to the tokens — this token is a number, that token is a string literal, this other token is an equality operator. A parser takes … Read more
What parsers and lexers have in common: They read symbols of some alphabet from their input. Hint: The alphabet doesn’t necessarily have to be of letters. But it has to be of symbols which are atomic for the language understood by parser/lexer. Symbols for the lexer: ASCII characters. Symbols for the parser: the particular tokens, … Read more
To extract the audio stream without re-encoding: ffmpeg -i input-video.avi -vn -acodec copy output-audio.aac -vn is no video. -acodec copy says use the same audio stream that’s already in there. Read the output to see what codec it is, to set the right filename extension.