[csswg-drafts] [css-values] Math Constant phi for Golden Ratio (#4702)

Crissov has just created a new issue for https://github.com/w3c/csswg-drafts:

== [css-values] Math Constant phi for Golden Ratio ==
Since predefined constants inside `calc()`, starting with `pi` for π and `e` (natural logarithm base), are now a thing #4688, there should also be `phi` for φ or ϕ which denotes ½+√1¼ ≈ 1.618034, i. e. the [Golden Number (also known as Golden Ratio or Golden Mean)](https://en.wikipedia.org/wiki/Golden_ratio) which is used a lot in graphic design, although often approximated by more practical, rational values between 1.6 (8:5) and 1.625 (13:8), e. g. in aspect ratios.

Itʼs such an obviously sensible addition that others have informally suggested it as well, of course, e. g. on [Twitter](<https://twitter.com/letrastudio/status/1219965138599583744?s=19>). 

Other constants that are *not* being proposed 

I can think of no other irrational factor frequently used in design that is not easily expressed as `sqrt()` with a simple argument like 2 or 0.5. 

The Silver Ratio is `1+sqrt(2)`, which is a little bit more complex, but is neither used very often nor does it have a commonly known symbol – δ<sub>s</sub> would become `delta-s` which is just one character shorter. 

The definition of the Platin Number (ρ or ϱ, `rho`, ca. 1.324717) is a lot more complex, but is neither well known nor often used. 

The other metallic means, `(p+sqrt(4*q+p*p))/2` with small integers `p` and `q`, are either simple numbers or not important at all. (p = q = 2 for platinum)

`tau` τ = 2π is too simple to deserve a designated constant of its own and itʼs already available as the angular unit `turn` anyway.

Uppercase Φ is usually just `1-phi` = `-1/phi`, sometimes also defined as `phi-1` = `1/phi`, but since CSS is case-insensitive here, it couldnʼt be added anyway. 

`theta` θ or ϑ is sometimes defined as  `sqrt(pi)*phi`, which is both now simple to write if one needs it and too hardly known otherwise.

There are, however, some standard angles, including the Golden Angle of c. `137.5deg` or c. `2.4rad`, that might make sense to add, but they would deserve an issue of their own. 

Please view or discuss this issue at https://github.com/w3c/csswg-drafts/issues/4702 using your GitHub account

Received on Saturday, 25 January 2020 11:18:27 UTC