2.5 DynAlgebra

This is a Dynamic Algebra [Nicaud1], “algebraic calculations on a computer by direct manipulation”, app available at http://r-gaia-cs.github.io/DynAlgebra/. The idea of Dynamic Algebra is about twenty years old and could help students to learn formula structure and transformations and help every users to produce step by step calculations. However, most of the previous implementations have not been successful.

The last known implementation of Dynamic Algebra was done in EpsilonWriter [Nicaud2] as a Java application and covers:

internal drag & drop

like converting $x+y$ into $y+x$,

external drag & drop

like dropping a formula on another formula,

on click calculation

like converting $x+x$ into $2x$ by click on $+$ and

rewriting rules

like converting $x^{-n}$ into $\frac{1}{x^n}$.

Our app, written in Javascript, is still at a prototype level compared to EpsilonWriter since it only partially covers the “on click calculation” and does not have a WYSIWYG input interface (currently TeXZilla is used). However, it uses MathML as storage format, which makes possible to work in documents not intended to be used for Dynamic Algebra.