Chop chop

[yaxu]

Improved chop, that respects existing begin/end controls (e.g. from a previous chop).

[felixroos]

nice one. I've been thinking this could be nice to have for slice as well, e.g. first cutting file to loop with begin / end, then slicing the loop instead of the whole file

[yaxu]

Yes also striate, which I think is extra useful as doing a series of striates doesn't just multiply up the slices as with chop.