## You're reading: Posts Tagged: interactive doodad

### Now I’m calculating with constructive reals!

A while ago I made myself a calculator. I don’t know if anyone else uses it, but for the particular way I like doing calculations, it’s been really good. You’d think that if a calculator does anything, it should perform calculations correctly. But all calculators get things wrong sometimes! This is the story of how I made my calculator a bit more correct, using constructive real arithmetic.

One thing you need to think about when making a calculator is precision. How precise do the answers need to be? Is it OK to do rounding? If you do round, then it’s possible that errors accumulate as you compose operations.

I’ve always wanted to make a calculator that gives exactly correct answers. This isn’t strictly possible: there are more real numbers than a finite number of bits of memory can represent, or a digital display can show, no matter how you encode them. But I’m not going to use every real number, so I’ll be happy with just being correct on the numbers I’m likely to encounter.

### Colourful Mathematics – A Review of Alex Berke’s Book ‘Beautiful Symmetries’

Group theory is a strange and wonderful area of study in mathematics, with plenty of key ideas and core concepts for one to wrap their algebra-hungry head around. But how do you introduce these algebraic constructs to beginners in a fun and engaging manner, whilst simultaneously providing a thoughtful read for the experts? This is exactly what mathematician and computer scientist Alex Berke accomplishes with her mathematical colouring book Beautiful Symmetry and its innovative group colouring concept.

### SAMDOB – mess up the order of operations

While I’m on strike, I’m catching up on stuff I’ve made but never posted about here.

At the Talking Maths in Public conference last August, I was talking with Katie Steckles and Kevin Houston about the order of operations. I think that another one of those ambiguously-written sums had gone round Twitter again. I said it would be good to have a tool where you can write an expression, then change the order of operations and see what happens.

So, on the way home, I wrote one! I’ve called it SAMDOB, which is an anagram of BODMAS.

Please have a play with it. I can imagine that this could be useful to people teaching the order of operations in real life. Let me know if you have any suggestions for improvements.

### The incredible palindromic hat-trick

I’ve made another one of my interactive online maths doodads. You should have a go at it right now. It doesn’t require any effort on your part, other than coming up with a positive integer.