Hi all, am toying around with the thought of generating core.logic
queries dynamically. However, I'm stuck at square one since all
the core.logic functions are macros and am not sure how to refer
to logic vars within a query generator fn.
E.g. given this list of facts...
(def myfacts
[[:karsten :spouse :mia]
[:fred :spouse :anna]
[:mia :name "mia"]
[:anna :name "anna"]])
...I'd like to find the person who's spouse's name is "mia".
The SPARQL[1] equivalent for the above would be:
SELECT ?p WHERE { ?p :spouse ?s . ?s :name "mia" }
In core.logic I can do this equivalently, but have no idea how to
generate the lists of `conso`s dynamically:
(run* [p]
(fresh [s]
(conde
[(conso p [:spouse s] (myfacts 0))]
[(conso p [:spouse s] (myfacts 1))]
[(conso p [:spouse s] (myfacts 2))]
[(conso p [:spouse s] (myfacts 3))])
(conde
[(conso s [:name "mia"] (myfacts 0))]
[(conso s [:name "mia"] (myfacts 1))]
[(conso s [:name "mia"] (myfacts 2))]
[(conso s [:name "mia"] (myfacts 3))])))
; => (:karsten)
a) How would I go about generating such a single `conso` only given a
single logic var, var position in the triple and the fact triple
itself?
b) How can I refer to a logic var in a function outside the lexical
scope of `fresh` or `run*`?
c) What is the best way to produce and pass a seq of goals for `conde`? Since
it is a macro I can't use `apply`...
K.
[1] http://www.w3.org/TR/sparql11-overview/
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