Description

SimpleFold iterates over Unicode code points equivalent under the Unicode-defined simple case folding. Among the code points equivalent to rune (including rune itself), SimpleFold returns the smallest rune > r if one exists, or else the smallest rune >= 0.

For example:

SimpleFold('A') = 'a'
SimpleFold('a') = 'A'

SimpleFold('K') = 'k'
SimpleFold('k') = '\u212A' (Kelvin symbol, K)
SimpleFold('\u212A') = 'K'

SimpleFold('1') = '1'