pattern bookByDescription(book:Book, description:EString, keyword) {
Book.description(book, description);
EString(keyword);
check((description as String).contains(keyword));
}

pattern bookByDescription(book:Book, description:EString, keyword:EString) {
 Book.description(book, description);
 check(description.contains(keyword));
}

Additionally, the semantics of this pattern dictates that 'keyword' be an EString _that is actually present_ in your instance model as some attribute value (of type EString). Therefore, it will not work in the way you might expect: it will only return those matches where the substitution for the variable 'keyword' is present in your model in some way.

At the moment, the way of operation you would like is not supported; essentially, information is only allowed to go "into" a check() constraint from an object that is part of your instance model. (Additionally, in your interpretation, this pattern would require IncQuery to enumerate _all possible substrings_ of your EStrings, which would be a very costly operation.)

pattern bookByDescription_Lord(book:Book, description:EString) {
 Book.description(book, description);
 check(description.contains("Lord"));
}

pattern bookByDescription(book:Book, description:EString) {
 Book.description(book, description);
}

BookByDescriptionMatcher m = new BookByDescriptionMatcher(...);
m.forEachMatch(new BookByDescriptionProcessor() {
 public void process(Book book, EString description) {
   // do something, e.g. collect Books by looking into their description
 }
});

Hi Emre,

Quote:

pattern bookByDescription(book:Book, description:EString, keyword) {
Book.description(book, description);
EString(keyword);
check((description as String).contains(keyword));
}

this is better written as

pattern bookByDescription(book:Book, description:EString, keyword:EString) {
 Book.description(book, description);
 check(description.contains(keyword));
}

Note that the type cast to String is not necessary.

Hi Emre,

Additionally, the semantics of this pattern dictates that 'keyword' be an EString _that is actually present_ in your instance model as some attribute value (of type EString). Therefore, it will not work in the way you might expect: it will only return those matches where the substitution for the variable 'keyword' is present in your model in some way.

At the moment, the way of operation you would like is not supported; essentially, information is only allowed to go "into" a check() constraint from an object that is part of your instance model. (Additionally, in your interpretation, this pattern would require IncQuery to enumerate _all possible substrings_ of your EStrings, which would be a very costly operation.)

If I am understanding this right, the reason why this function fails, is that the IncQuery sees the keyword parameter as an attribute of a class from the model, so it strictly checks for EString attributes, which matches with the given value?

Isn't there some sort of a workaround, like using helper parameters, which IncQuery doesn't interpret as class attributes from the model, so we can use them in check() clauses, to filter found results further and return them as results? Or every parameter in the pattern signature will be interpreted as attributes/classes from the model?