[Top][All Lists]

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

foldts for building graphs

From: Catonano
Subject: foldts for building graphs
Date: Thu, 19 Mar 2020 13:22:59 +0100

I'd like to build a tree that has the exact same shape of the tree made of
tree-il records

BUT I want my tree to be made of cons cells and vectors. No more

So lists, alists and vectors.

But no more.

Because those can be pretty printed.

tree-il trees can be printed but they're not so pretty

I'm using "tree-il-fold"

When going _down_ along a branch, I know what to do

I can add the visited node as a child of the previously visited node

The problem is when stepping _up_

Because in the accumulator I think I should track the fact
that the visiting process is currently on a node that is a step up
in regard to the previous visiting step

Shouldn't I ?

I don't know how to do this

In Clojure I would have represented my accumulator as a map
and I would have marked the "current" node with a key value couple,
with something along the lines of

[curly brackets are like parenses but for dictionary like structures in

{... {... {... #:current? #t ...}   ...}   ...}

Clojure maps are immutable so a new map would be created at every recursion

But behind the curtains, the structure doesn't get replicated as a whole,
but rather versioned

and the new versions share some memory with the previous ones

This is what happens with vanilla list processing in scheme

so writing purely functional code is convenient (easy, compact)
and not so wasteful

In Guile such a facility doesn't exist, as far as I understand

Should that not work, in Clojure there are also the so called zippers

Neither zippers are available in Guile, as far as I understand

So how do I do this ?

How do I replicate a tree-il based tree in vanilla cons cells ?

maybe I should take a look at lenses ?

I still didn't study them

Thanks in advance

reply via email to

[Prev in Thread] Current Thread [Next in Thread]