I merged my implementation of the SVGEllipticalArc class into path.h substituting the old one. Some method lacks of a native implementation, yet and it relies on a conversion to SBasisCurve, but the class is fully working (there isn't any not_implemented exception thrown any more). Moreover I commit a new version of the svg-elliptic-arc-toy, with the ability of testing the portion method too.
PAY ATTENTION ! I want to point out that I modified the src/CMakeList.txt file, adding some line of code in order to find out which version of ragel is installed. This is needed because starting from version 5.18 the ragel package substituted the command rlcodegen with the rlgen-cd command as specific code generator back-end for C, C++ and D languages. If you'll get into troubles when you build the library you'd look that you have the ragel package installed. Anyway in case of problem you can send me a mail or contact me on the lib2geom channel.
Regards, Marco