Text previous double character- Ti

- Instruction: Ti - Parameter: none - Return: true if the previous two characters are equal - Description: Returns true if the two characters preceding the index are equal, that is, they are doubles. For example, if there is a pair "bb" before the index, the instruction returns true. This instruction does not want any other parameters, since the doubles detected can be any character. - Examples: Text string: a Braille string: 456 Condition: Ti Description: The character "a" is transcribed with the cell "456" if it is preceded by a pair of equal characters, such as "bb", "ll", "55" etc..