ssp

How to extract a single file with its history from a git repository

These steps show two less common interactions with git to extract a single file which is inside a subfolder from a git repository. These steps essentially reduce the repository to just the desired files and should performed on a copy of the original repository (1.).

First the repository is reduced to just the subfolder containing the files in question using git filter-branch --subdirectory-filter (2.) which is a useful step by itself if just a subfolder needs to be extracted. This step moves the desired files to the top level of the repository.

Finally all remaining files are listed using git ls, the files to keep are removed from that using grep -v and the resulting list is passed to git rm which is invoked by git filter-branch --index-filter (3.). A bit convoluted but it does the trick.

1. copy the repository to extract the file from and go to the desired branch

ofan

Lisp interpreter in 90 lines of C++

I've enjoyed reading Peter Norvig's recent articles on Lisp. He implements a Scheme interpreter in 90 lines of Python in the first, and develops it further in the second.

Just for fun I wondered if I could write one in C++. My goals would be

1. A Lisp interpreter that would complete Peter's Lis.py test cases correctly...
2. ...in no more than 90 lines of C++.

Although I've been thinking about this for a few weeks, as I write this I have not written a line of the code. I'm pretty sure I will achieve 1, and 2 will be... a piece of cake!