This module defines a parser for unit expressions. The syntax for these expressions is like F#'s. There are four arithmetic operators (*, /, ^, and juxtaposition). Exponentiation binds the tightest, and it allows an integer to its right (possibly with minus signs and parentheses). Next tightest is juxtaposition, which indicates multiplication. Because juxtaposition binds tighter than division, the expressions m/s^2 and m/s s are equivalent. Multiplication and division bind the loosest and are left-associative, meaning that m/s*s is equivalent to (m/s)*s, probably not what you meant. Parentheses in unit expressions are allowed, of course.

Within a unit string (that is, a unit with an optional prefix), there may be ambiguity. If a unit string can be interpreted as a unit without a prefix, that parsing is preferred. Thus, min would be minutes, not milli-inches (assuming appropriate prefixes and units available.) There still may be ambiguity between unit strings, even interpreting the string as a prefix and a base unit. If a unit string is amiguous in this way, it is rejected. For example, if we have prefixes da and d and units m and am, then dam is ambiguous like this.