When thinking of parsing math expressions (which can be thought of as kind of language interpretation), one should not give the Interpreter Pattern a miss. Interpreter is one of the design patterns originally described by the “Gang of Four”. It refers to interpreting some abstract language and it shows one of the ways of building an interpreter. The keynote is simple: write a class for each kind of symbol that may occur in expression, then instantiate those classes and connect the objects together so they will form a tree.
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