unstable-string-to-numberThe string->number procedure is supposed to parse
numbers out of strings and return them, or return #f if the
string is not a syntactically valid number. That leaves to interpretation
the corner case where the argument string contains a syntactically
legitimate expression for a number that nonetheless is not a number, namely
the likes of 1/0. Should string->number return
#f or fall through to the number construction (which will
presumably signal a division by zero)?