Code for identifying programming language in a text file [closed]

Answer 1

Since the list of languages is known upfront you know the syntax/grammar for each of them. Hence you can, as an example, to write a function to extract reserved words from the provided source code.

Build a binary tree that will have all reserved words for all languages that you support. And then just walk that tree with the extracted reserved words from the previous step.

If in the end you only have 1 possibility left - this is your language. If you reach the end of the program too soon - then (from where you stopped) - you can analyse your position on a tree to work out which languages are still the possibitilies.

Answer 2

If you know that the source files will conform to standards, file extensions are unique to just about every language. I assume that you've already considered this and ruled it out based on some other information.

If you can't use file extensions, the best way would be to find the things between languages that are most different and use those to determine filetype. For example, for loop statement syntax won't vary much between languages, but package include statements should. If you have a file including java.util.*, then you know it's a java file.

Answer 3

As dmckee suggested, you might want to have a look at the Unix file program, whose source is available. The heuristics used by this utility might be a great source of inspiration. Since it is written in C, I guess that it qualifies for C++. :) You do not get confidence percentages directly, though; maybe are they used internally?

Answer 4

Take a look at nedit. It has a syntax highlighting recognition system, under Syntax Highlighting->Recognition Patterns. You can browse sample recognition patterns here, or download the program and check out the standard ones.

Here's a description of the highlighting system.

Answer 5

One simple solution I could think of is that you could just identify the keywords used in different languages. Each identified word would have score +1. Then calculate ratio = identified_words / total_words. The language that gets most score is the winner. Off course there are problems like usage of comments e.t.c. But I think that is a very simple solution that should work in most cases.

Answer 6

You can maybe try to think about languages differences and model these with a binary tree, like "is feature X found ? " if yes, proceed in one direction, if not, proceed in another direction.

By constructing this search tree efficiently you could end with a rather fast code.