Support other string functions and operators

[rlaiola]

Reference issue

None.

What does this implement/fix?

This PR adds support to some useful string functions and operators found in major RDBMSs. These are:

• REGEXP: Whether string matches regular expression
• RLIKE: Synonym for REGEXP
• REPEAT(): Repeat a string the specified number of times
• REPLACE(): Replace occurrences of a specified string
• REVERSE(): Reverse the characters in a string

The implementation includes unit tests and has been based mainly on the MySQL specification, although PostgreSQL an SQL Server follow a very similar approach (references included below).

How to test this PR?

Test it live at https://rlaiola.github.io/relax/calc/local/uibk/local/0. For automated tests visit https://rlaiola.github.io/relax/test.html

References

• https://dev.mysql.com/doc/refman/8.0/en/string-functions.html
• https://www.postgresql.org/docs/15/functions-string.html
• https://learn.microsoft.com/en-us/sql/t-sql/functions/string-functions-transact-sql?view=sql-server-ver16
• https://learn.microsoft.com/en-us/sql/t-sql/language-elements/like-transact-sql?view=sql-server-ver16

[DeepakKumarKhatri]

This is really a good PR.
I was searching for these methods.
I hope the maintainer merges it soon.

[evazangerle]

thank you

[rlaiola]

@evazangerle it seems that this PR has not been merged into development.