chickadee » scheme » char=?

These procedures impose a total ordering on the set of characters. It is guaranteed that under this ordering:

• The upper case characters are in order. For example, (char<? #\A #\ B) returns #t.
• The lower case characters are in order. For example, (char<? #\a #\ b) returns #t.
• The digits are in order. For example, (char<? #\0 #\9) returns #t.
• Either all the digits precede all the upper case letters, or vice versa.
• Either all the digits precede all the lower case letters, or vice versa.

Some implementations may generalize these procedures to take more than two arguments, as with the corresponding numerical predicates.