Alt text on math symbols

[ptarjan]

I'm not sure how you generate your math symbols, but they are rendered as images what an alt text of "". That means if I copy and paste the problem into the top of my source code, I get blanks wherever the images are. If you can set the alt text to be a good representation of the symbol, that would make it much more accessible and easier to put as the header for my source code.

Example:

http://projecteuler.net/images/symbol_le.gif could have alt text "<="

Thanks. Its just kinda funny to see the top of my source code : For 1 k 55, sk = [100003 200003k + 300007k3]. Hard to figure out what I was doing.

Thanks for the great side. I'm really enjoying it.

Paul

[euler]

I've learned something new today! I hadn't realised that when web content is copied and pasted into a text editor that the images are replaced with the "alt" text; thanks for that, ptarjan.

Anyway, you'll be pleased to see that the HTML entity name is now contained in the alt value. Just a shame about superscript and subscript text now.

[ptarjan]

Thanks for the fast reply, and the REALLY fast implementation, looks great

I was playing with a few ways to do the sup and sub, and I came up with:

c<img style='display:none' alt='**'/>²

or you could use "^" instead of "**". Similarly, "_" could be for sub.

Or if you want to get fancy, you can put a "(" to the left and ")" img to the right. Up to you.

I don't know if it is worth it to you, but it does make copying and pasting nice

http://fileserver.paulisageek.com/test/sup.html

Thanks again.

Paul

[elendiastarman]

What would happen if you did "2^2^2^2"?

[euler]

I got fancy.

Unfortunately, I've discovered that this is only works in Firefox. However, unlike the typical statistics found on the internet, it is interesting to note that around 60% of our members use Firefox. So those with good taste will reap the benefits.
(FYI, around 20% of our members use IE, and the rest use Safari, Opera, and others in that order.)

What would happen if you did "2^2^2^2"?

It would appear as 2^(2^(2^(2)))).

[ptarjan]

Looks great, thank you euler.

Also, I'm happy to see the browser statistics I'll check it in IE6-8 when I get home and see which copys the alt text. Some might use the title text. I'm not sure if there is a standard, or even if there is a de-facto standard.

Anyways, thanks a ton for being so responsive. I love this site!

[sigh]

Wow, that's pretty cool . Thanks for all the work you do, euler.

Btw, now some of the problems look a bit funny now:

By listing the first six prime numbers: 2, 3, 5, 7, 11, and 13, we can see that the 6^(th) prime is 13.

What is the 10001^(st) prime number?

It doesn't really bother me, but I thought I'd mention it in case you didn't intend for this. This issue arises in quite a few problems.

[hk]

I don't see anything weird when viewing the text of problem 7 in IE8, Firefox and Opera. All is as should be.
I presume that, as far as copying is concerned, the text between ^and is translated into ^(..).
I don't see any way of doing it otherwise and I think the guys that insist on copying should interpret it back that way.

[sigh]

I didn't mean to imply that it should be one way or another, or that it was behaving differently to how euler described.

I was just pointing out that rendering x^(2) correctly also has the side effect of rendering things like 1^st as 1^(st) and ¹/₇ as ^(1)/_(7).

It's possible that these cases were overlooked when deciding what to implement, so I pointed it out on the chance that you hadn't considered it and didn't think it desirable.

[stijn263]

What would happen if you did "2^2^2^2"?

I was wondering, what is the value of 3^3^3 ? Is it 3^27 or 27^3? Maple returns:

Error, ambiguous use of `^`, please use parentheses

[elendiastarman]

I always go with latest-first.
So, in my opinion, 3^3^3 = 3^27.

[rayfil]

What would happen if you did "2^2^2^2"?

This one would be irrelevant. Being ambiguous, such a statement would NEVER be used in the definition of a PE problem.

[uws8505]

I was wondering, what is the value of 3^3^3 ? Is it 3^27 or 27^3? Maple returns:

Error, ambiguous use of `^`, please use parentheses

Mathematica gives 3^3^3 = 3^27 = 7625597484987, not 27^3 = 19683. Maybe the order of ^ operation is right-to-left.

[xan]

Being ambiguous, such a statement would NEVER be used in the definition of a PE problem.

When typeset, I think the font sizing clarifies things. If each 2 is smaller than the previous, then it's right-to-left. Closest I can find in PE is Problem 197 (View Problem). There's a quadratic binomial in the exponent, but I can't repeat the formula here since the forum software doesn't seem to support nested ^tags.

[euler]

But copying and pasting it using Firefox gives the expected (flat) equivalent: f(x) = ⌊2^(30.403243784-x^(2))⌋ × 10^(-9)

[Georg]

I was wondering, what is the value of 3^3^3 ? Is it 3^27 or 27^3? [...]

[...] So, in my opinion, 3^3^3 = 3^27.

[...] Being ambiguous, [...]

[...] Maybe the order of ^ operation is right-to-left.

[...] If [...] then it's right-to-left.

In mathematics, exponentiation of real numbers is a right-associative operation.

In programming languages, the associativity of an operator depends on the programming language in question.

[xan]

I did a survey of programming languages a while back when I was writing an interpreter for a scripting language and found there was no universal agreement among them about left or right associativity for the exponentiation operator. VisualBasic, I think, is one where it's left-associative.

[elendiastarman]

What are the advantages of left- over right- associativity?

[DNS]

I don't see anything weird when viewing the text of problem 7 in IE8, Firefox and Opera. All is as should be.
I presume that, as far as copying is concerned, the text between ^and is translated into ^(..).
I don't see any way of doing it otherwise and I think the guys that insist on copying should interpret it back that way.

I haven't seen it too, but in time when LAN Internet had problems, I use my smartphone (with "small-opera"). There I see problems.