TUTORIAL-TUPLES.md

TRLC Tutorial (Tuples)

This is part of the TRLC Tutorial.

Tuples

TRLC allows you to create used-defined algebraic datatypes, generally referred to as "tuples". For example:

type Coordinate {
   x Decimal
   y Decimal
}

type Requirement {
   description String
   coordinate  Coordinate
}

This allows us to specify inline bundled data in a convenient way. You can now write:

Requirement potato {
   description = "draw something here"
   coordinate  = (42.0, 0.666)
}

Tuples can contain any kind of data, including other tuples; but it is not possible to have array fields or create recursive tuples.

Syntactic sugar

There is one additional form for tuples that can be used to allow convenient inline writing of simpler tuples. Consider a pairing of an item plus its version:

tuple Codebeamer_Id {
   item    Integer
   separator @
   version optional Integer
}

When using this syntax, then tuple instances you write can be much shorter, for example:

   derived_from_codebeamer = [ 12345,
                               555@42 ]

Both of these are instances of Codebeamer_Id, the first one is has version set to null, and the second one has version set to 42.

There two important rules:

• Only tuples with separator may have optional fields

• Once a field is optional, all following fields must also be optional

Writing checks

You can also write checks for tuples, just like you can for record types. For example:

checks Codebeamer_Id {
   item >= 1,
     error "CB Item must be positive", item

   version != null implies version >= 1,
     error "CB Version must be positive", version
}

In other checks you can access tuple fields using the . notation:

checks Requirement {
   (forall cb_item in derived_from_cb =>
      cb_item.item >= 50000),
   warning "this item is suspiciously low"
}