(char val)
  val: any type
  returns a char

Converts its argument to a character.

• If the argument is already a character, this function is a no-op.

• If the argument is an integer in the range 0x0000 ..= 0xD7FF or 0xE000 ..= 0x10FFFF, returns the character with that Unicode scalar value.

• If the argument is a floating-point number, it's converted to an integer, then converted to a character as above.

• Any other argument is an error.