MathML to Plain Text Converter

Introduction

There seem to be few resources converting MathML code into plain text. A good reason is there is no consensus in how to format some math expressions. But for many expressions involving (+,-,/,*,^,=) operators, here is one possible converter.

The Classes Engaged

• Class MathToString prepares the string with the MathML code so that class ParseML can perform the detailed parsing.

Preparation

First, the spaces are replaced by empty strings and some special characters are replaced too. Also, some tags not involved in the math expression, like style tags, are removed. Then any <mfrac> tag, that stands for a fraction, this is parsed first and replaced in the input string in between "|" characters so that later it can be recovered by ParseML class.

Using the Code

To convert, just call the shared method MathToString.convertToString():

Dim converted as String = MathMLToString.convertToString(MathMLcodeToConvert)

Basic Principles

The parsing method is a recursive-descent parsing: Parsing Expressions by Recursive Descent.

Evaluation method E calls T for any addition or substraction, but T calls first F for any multiplication or substraction, and F calls first P for any power possible power operation. P calls first v to get next token. If there is a "(" token, v calls recursively to T.

E --> T {( "+" | "-" ) T}
T --> F {( "*" | "/" ) F}
F --> P ["^" F]
P --> v | "(" E ")" | "-" T

History

• 12th May, 2022: Initial version