Allow vertical bar notation for absolute value

[Kourser]

syntax example

| −y + 12 | = 1

result

SyntaxError: Value expected (char 1)

expected result

y=11,
y=13

[m93a]

Currently, math.js doesn't have an equation solver – neither for absolute value equations, nor for anything else. But I'm sure we'll get there some day.

Btw, the syntax for absolute value is abs(x), not |x|.

[gwhitney]

The kernel of this that I can see is a proposal that the parse allow |y+12| as an alternate notation for abs(y+12). That would certainly mesh well with standard mathematical notation. No idea off the top of my head whether it is actually feasible in the parser or not -- could easily imagine things like |x|y|| (intended to be abs(x*abs(y))) being hopelessly confusing to parse because sadly absolute value bars don't have matching open and close versions. Anyhow, retitling the issue to reflect this and moving it to Discussions.

[gwhitney]

This exact same issue also came up as #1307, where there is a more in-depth discussion that points out that a|b is also bitwise OR, making parsing here quite possibly hopeless. But we can leave the discussion open for others who have a similar idea, and maybe someone will come up with a workable proposal.