Conversion of Units of Measurement

This program converts between different units of measurement, or combinations of units.

A unit expression is:

a unit name, such as meter . Common abbreviations such as ft or mph are allowed.
a number such as 2.5 or kilo
a product of unit expressions, (* unit₁ ... unit_n)
a quotient of two unit expressions, (/ unit₁ unit₂)

For example, a speed of 60 miles per hour could be represented as (* 60 mph) or
(* 60 (/ mile hour)) .

For temperature conversions, the source must be a product such as (* 50 F) and the goal must be a temperature unit such as C.

Instructions: