Add Tau constant to core Math class

[DartBot]

This issue was originally filed by peter.gers...@gmail.com

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With a new language, we are taking the opportunity to introduce better concepts, right? So please add Tau, the ratio of a circle's circumference to its radius (i.e. 2pi), to the Math class.

Leave Math.PI as is, but please add Math.TAU

This is a safe addition with no side effects and minimal impact to the language and runtime.

Tau manifesto: http://tauday.com/

[DartBot]

This comment was originally written by jat@google.com

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[DartBot]

This comment was originally written by drfibonacci@google.com

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We should add PHI while we're at it :-)

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[DartBot]

This comment was originally written by drfibonacci@google.com

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Added Triaged label.

[DartBot]

This comment was originally written by realJT...@gmail.com

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How about Math.AnswerOnTheUltimateQuestionOfLifeTheUniverseAndEverything (i.e. 42)? This is a safe addition with no side effects and minimal impact to the language and runtime.

[gbracha]

Removed Area-Language label.
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[DartBot]

This comment was originally written by Sebastian.zi...@gmail.com

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TAU is an important constant, which frequently gets used many times inside a loop. Only having pi, would encourage people to do 2*pi inside that loop, which would (slightly) degrade performance, and will be bad for readability. Plus the tau manifesto DOES make some good points.

[DartBot]

This comment was originally written by Sebastian.zim...@gmail.com

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Both TAU and PHI are used in the sunflower sample, which perfectly illustrates their importance in even the most basic graphical application.

[DartBot]

This comment was originally written by wekiel...@google.com

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As noted in the "Tau Manifesto" http://tauday.com/#sec:the_number_tau Math textbooks use 2Pi instead of Tau. It's more readable to continue to be consistent with the textbooks and see 2Pi everywhere.

[DartBot]

This comment was originally written by bruck.micha...@gmail.com

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Comment 8 advocates for abolishing all Dart language features that can be represented by other syntax currently used in textbooks. No =>, no short constructor syntax etc.

[DartBot]

This comment was originally written by iambo...@gmail.com

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I'm normally conservative about certain things. For instance, when Pluto was no longer a planet, it annoyed me. When people mispronounce "zoology" or say "10 items or less" instead of "10 items or fewer", it irks me. However, after reading about Tau, I have to agree that this is a worthwhile constant to include.

Jokes aside (Math.AnswerOnTheUltimateQuestionOfLifeTheUniverseAndEverything has a place in good literature, not in mathematics), if someone wants to be consistent with textbooks, they can continue to use Pi. There is nothing that would stop a Pi fan from continuing to use Pi. For Tau fans, there will also be an option. Otherwise, Tau fans would need to define Tau in all applications, adding additional overhead.

As for 2Pi degrading performance, one would expect that the compiler could be intelligent enough to recognize when two constants/literals are involved in a calculation that it could combine these into a single representative constant where appropriate. So, I don't believe performance is a valid argument unless the compiler isn't smart enough to deal with 2Pi appropriately.

That aside, from a "it just makes sense" standpoint, Math.TAU should be included.

[DartBot]

This comment was originally written by jjb@google.com

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I don't believe we should include this constant. It's obscure, even among the most skilled programmers, and we want Dart to appeal to the broad mass of programmers. The great majority of programmers would have an easier time
reading "2 * Math.PI" than "Math.TAU". I believe it would be actively harmful to add this constant, as it would encourage programmers to write programs that other programmers could not read. The costs outweigh the benefits.

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[DartBot]

This comment was originally written by amati...@gmail.com

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Do you really think than:

degreeToRadians(num degree) {
  return degree * Math.TAU / 360;
}

Cannot be readed while

degreeToRadians(num degree) {
  return degree * Math.PI / 360 / 2;
}

Or to keep it as a simple cross-multiplication:

degreeToRadians(num degree) {
  return degree * Math.PI / 180;
}

First time I see this operation I was so confused, what's 180? Arent the total degrees 360? why just the half?

[DartBot]

This comment was originally written by iam...@gmail.com

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I think what's being said here is that it has nothing to do with how readable the math is. It's that the dart language isn't here to solve issues with constants, it's here to gain the most traction with developers. More developers are familiar with the use of Math.PI than are developers who are familiar with the concept of TAU, which is a relatively new concept.

I agree that TAU is gaining traction and, in terms of mathematics, it just makes sense. However, if just 5% of developers out there have never heard of TAU, they're going to be more confused about this strange constant than they'd be about the example you gave, which is what users of pi have already been dealing with for decades.

[DartBot]

This comment was originally written by jjb@google.com

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Sorry, my last comment was mangled by email gateway; I'll try again:

Comment #­12 on issue #14 by amati...@gmail.com: Add Tau constant to core Math class
http://code.google.com/p/dart/issues/detail?id=14

| Do you really think than:
|
| degreeToRadians(num degree) {
| return degree * Math.TAU / 360;
| }
|
| Cannot be readed

Yes. People won't know what it means.
 
| while
|
| degreeToRadians(num degree) {
| return degree * Math.PI / 360 / 2;
| }
|
| [can be read]

The above is nasty (the sequence of divisions), but I don't think anyone skilled in the art would actually write it.

| Or to keep it as a simple cross-multiplication:
|
| degreeToRadians(num degree) {
| return degree * Math.PI / 180;
| }

The above is just fine. In fact, it's an idiom. A google search for "Math.PI / 180" turns up 2.7 MILLION hits. If we wanted to shorten it, we could provide Math.degreesToRadians and radiansToDegrees methods, but I'm not sure it's worth adding these convenience functions.

    Josh

[DartBot]

This comment was originally written by gtg...@gmail.com

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Maybe it's just me, and maybe i'm not as "skilled" of a programmer as you 1337 hax0rs, but when i come across something i'm not familiar with in code, I use this thing called "Google" to "search" the "internet" and "learn" information about it.

While I know it's not the goal of the Dart language to "educate" people or to force them to "learn" something new, since everyone who knows a shred of programming will obviously understand all dart code without having to learn any new syntax or keywords or design patterns, I can't garner why there are so many "haters" out there who don't want a measly constant added to Math.

Who are you to tell others how to write their code? Just because you think you're more skilled and know better than me, why are you forcing me to use PI when I might want to use TAU instead? It's not like we're talking about removing PI, FFS.

Let's just add TAU and move on with life.