[Jprogramming] Intro to "under"

[Björn Helgason]

2012/1/6 Roger Hui <rogerhui.canada at gmail.com>

> See http://www.jsoftware.com/jwiki/Essays/Under for examples of under.
>
>
I see gi is defined now

  f&.g y [image: $\leftrightarrow$] gi f g y
x f&.g y [image: $\leftrightarrow$] gi (g x) f (g y)
where gi is the inverse of g . "Under" elucidates the important but often
mysterious concept of duality in mathematics.

Sometime long time ago I remember speculating what this gi was.

Either it was not defined in the text or I failed to find it.