Choosing the best language to build your AI chatbot

From submitter Christoph comes a function that makes your average regex seem not all that bad, actually: According to "What is a Titration?" Since this is an often needed calculation in a laboratory, we can write a program to solve this problem for us. Part of the solver is a formula parser, which needs to accept variable names (either lower or upper case letters), decimal numbers, and any of ' -*/ ()' for mathematical operators. Presented here is the part of the code for the solveTitration() function that deals with parsing of the formula. Try to read it in an 80 chars/line window.