kral | Social media crawler | Crawler library

Because res.headers is an object, you can use objectName["propertyName"] to get icy-url (or objectName.propertyName, but because of the - I'd use the first one.

So, this would be:

I hope this can help

The usually named soft-cut control construct is available in several Prolog systems. CxProlog, ECLiPSe, JIProlog, SWI-Prolog, and YAP provide it as both a *->/2 predicate and infix operator. Ciao Prolog, SICStus Prolog, and YAP provide an if/3 predicate with the same semantics.

My main use of this soft-cut control construct is in the implementation of coinduction in Logtalk, where it plays a critical role. Outside of this case, I rarely use it.

The ->/2, on the other hand, it's widely used. The implicit cut in the if part is local to the construct and its usage avoids, as in your example, trying to prove the guard twice, which can be computationally expensive. It may not be pure but, as with the cut, as long as you're fully aware of its pros and cons, it's a useful control construct.

P.S. Logtalk provides unit tests for this control construct for the *->/2 variant at https://github.com/LogtalkDotOrg/logtalk3/tree/master/tests/prolog/control/soft_cut_2_3 and for the if/3 variant at https://github.com/LogtalkDotOrg/logtalk3/tree/master/tests/prolog/control/if_3

FOUND THE ANSWER:

From you comment:

binary '<<' : no operator found which takes a right-hand operand of type 'CardColor' and 'CardValue' (or there is no acceptable conversion)

You also need to provide operator<< for the Color and Value class.

example of this for the Color class:

Since you added relationship between your nodes, the query can be greatly simplified.

We need paths from each instructor to child instructors up to 3 levels down, and depending on how far down, we can get the appropriate percentage to run the calculations on the given transactions, then sum it all up.

Here's an example query that should work, though it will report on any instructor with at least one child instructor, instead of only instructors with at least 3 levels down of child instructors.