I expect that each time I call :viral_load, it takes whatever
value :epitopes or :mutations has at that point in time,
I can indeed write a function outside of the map that does the
calculation, but I found the idea of an embedded function neat. Also
writing a function only works as long as there is a limited number of
functions in the model that describes how epitopes and mutations
translates to viral load. However, if you would want to do something
like an evolvable trade-off between epitopes and mutations in viruses,
you would like to be able to store the functions inside each virus.
On Dec 9, 8:40 pm, ataggart <alex.tagg...@gmail.com> wrote:
> On Dec 9, 10:20 am, bOR_ <boris.sch...@gmail.com> wrote:
>
>
>
>
>
> > Hi all,
>
> > I want to make a hash-map where the value of one key depends on the
> > values of other keys in the hash-map. Is there a way to do this,
> > without needing an external reference to the hash-map?
>
> > {:a 1 :b 2 :c #(+ :a :b)}
>
> > Similarly, when filling a struct, I often want to refer to the bits I
> > already have filled in. I solve that now by just embedding the (struct
> > mything.. in a let, and just use the serial nature of let to calculate
> > for example c from a and b. Is there a way that while filling a struct
> > I can refer to it?
>
> > I would like to do this
>
> > (defstruct virus :epitopes :mutations :viral_load)
> > (def myvirus (struct virus 3 5 (+ (* 0.1 :epitopes) (*
> > 0.2 :mutations))))
>
> > Instead of
>
> > (defstruct virus :epitopes :mutations :viral_load)
> > (let [epitopes 3
> > mutations 5
> > viral_load (+ (* 0.1 epitopes) (* 0.2 mutations))]
> > (def myvirus (struct virus epitopes mutations viral_load))
>
> > As you can see there is some room for being more concise and compact
> > if you can refer to keys in the same hash-map or struct, even if the
> > hash-map / struct is still being constructed.
>
> Do you expect that modifying the values of :epitopes or :mutations
> should be reflected in the value of :viral_load? If not, then you
> could just write a custom function that creates virus instances
> instead of using struct, e.g.:
>
> (defn viral-load [epitopes mutations]
> (+ (* 0.1 epitopes) (* 0.2 mutations)))
>
> (defn make-virus [epitopes mutations]
> (struct virus epitopes mutations (viral-load epitopes mutations)))
>
> If you *do* want :viral_load to reflect changes in the other values,
> then I'd say you shouldn't include it in the struct. Actually, either
> way this seems to be a caching mechanism which is both orthogonal to
> the domain, and tends to be more trouble than it's worth in the long
> run. In short, smells like OO instead of FP, but I could be wrong.
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