lower and upper characters are vice versa

[korpa]

lower and upper characters are vice versa

[MikeMcl]

Are far as I am aware there is no one standard for this.

 // bignumber.js alphabet
 0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ$_

This library follows javascript's Number.prototype.toString in using lower-case letters to represent 10 to 35, which then leaves the upper-case letters etc. for the rest.

(255).toString(16);    // 'ff'

This seems simpler, and is easier to implement, then using lower-case letters for 10 to 35 for bases in the range 2 - 36 but upper-case letters for 10 to 35 for bases above 35, as gmp may do.

If you find a good reason for the gmp approach let me know.

Cheers.