Case-insensitive conversion of 'truthy' and 'falsey' input to '1' or '0'.
All other input is converted to 'UNDEFINED'.
Intended for use in `#ifexpr` templates.
e.g. {{#ifexpr: {{Bool | {{{input}}} }} | true | false }}
input-output table:
| input | output |
|---|---|
| {{Bool|}} | 0 |
| {{Bool|1}} | 1 |
| {{Bool|0}} | 0 |
| {{Bool|yes}} | 1 |
| {{Bool|no}} | 0 |
| {{Bool|true}} | 1 |
| {{Bool|false}} | 0 |
| {{Bool|Yes}} | 1 |
| {{Bool|YES}} | 1 |
| {{Bool|No}} | 0 |
| {{Bool|NO}} | 0 |
| {{Bool|True}} | 1 |
| {{Bool|TRUE}} | 1 |
| {{Bool|False}} | 0 |
| {{Bool|FALSE}} | 0 |
| {{Bool|other}} | UNDEFINED |