I totally agree. I looked at the keyboard and I couldn't find anything else. '$' would have been even worse...
And I think you might have to hack the MzScheme reader really deeply to make it accept '|' as a conventional character, since it is used to be able to embed special characters into symbols...
Yep. My margin annotations in the tutorial notes for composition read, "Kinda like pipe..."
Unless, pipe is reserved for something else why not implement it here? Assuming an english keymap is in use both the : and | require a shiftkey to enter and both use pinky finger to insert. Is the extra bit of reach an issue? Conceptually the|seems more apropos to composition and prob. more accessible to more potential adopters than the :. For me the|is an easier visual parse when scanning multiple lines of code. For me the:isn't as easy a visual parse when scanning multiple lines of code.