Views
A str points into someone's bytes and says whose.
main (bytes, print)
# str is a view into someone else's bytes. A function returning a view
# says which parameter it came from with `from`.
afterColon(text str) str from text
at = bytes.indexOf(text, ":") ?: 0 - 1
if at < 0
text
text[at + 1:len(text)]
main()
line = [byte: *"key:value"]
value = afterColon(line[0:len(line)])
same = bytes.equal(value, "value")
print.line("{value} {same}")value true