From f788256809537386b2371956dc4f88f1d9866462 Mon Sep 17 00:00:00 2001
From: Kyle Daruwalla <daruwalla@wisc.edu>
Date: Mon, 31 Oct 2022 11:25:09 -0500
Subject: [PATCH] Rebase with #39

---
 src/functor.jl | 75 --------------------------------------------------
 src/walks.jl   | 19 +++++++++++--
 2 files changed, 16 insertions(+), 78 deletions(-)

diff --git a/src/functor.jl b/src/functor.jl
index c89fd03..9c8cf78 100644
--- a/src/functor.jl
+++ b/src/functor.jl
@@ -34,81 +34,6 @@ isleaf(x) = children(x) === ()
 
 children(x) = functor(x)[1]
 
-function _default_walk(f, x)
-  func, re = functor(x)
-  re(map(f, func))
-end
-
-usecache(::AbstractDict, x) = isleaf(x) ? anymutable(x) : ismutable(x)
-usecache(::Nothing, x) = false
-
-@generated function anymutable(x::T) where {T}
-  ismutabletype(T) && return true
-  subs =  [:(anymutable(getfield(x, $f))) for f in QuoteNode.(fieldnames(T))]
-  return Expr(:(||), subs...)
-end
-
-struct NoKeyword end
-
-function fmap(f, x; exclude = isleaf, walk = _default_walk, cache = anymutable(x) ? IdDict() : nothing, prune = NoKeyword())
-  if usecache(cache, x) && haskey(cache, x)
-    return prune isa NoKeyword ? cache[x] : prune
-  end
-  ret = if exclude(x)
-    f(x)
-  else
-    walk(x -> fmap(f, x; exclude, walk, cache, prune), x)
-  end
-  if usecache(cache, x)
-    cache[x] = ret
-  end
-  ret
-end  
-
-###
-### Extras
-###
-
-fmapstructure(f, x; kwargs...) = fmap(f, x; walk = (f, x) -> map(f, children(x)), kwargs...)
-
-function fcollect(x; output = [], cache = Base.IdSet(), exclude = v -> false)
-    # note: we don't have an `OrderedIdSet`, so we use an `IdSet` for the cache
-    # (to ensure we get exactly 1 copy of each distinct array), and a usual `Vector`
-    # for the results, to preserve traversal order (important downstream!).
-    x in cache && return output
-    if !exclude(x)
-      push!(cache, x)
-      push!(output, x)
-      foreach(y -> fcollect(y; cache=cache, output=output, exclude=exclude), children(x))
-    end
-    return output
-end
-
-###
-### Vararg forms
-###
-
-function fmap(f, x, ys...; exclude = isleaf, walk = _default_walk, cache = anymutable(x) ? IdDict() : nothing, prune = NoKeyword())
-  if usecache(cache, x) && haskey(cache, x)
-    return prune isa NoKeyword ? cache[x] : prune
-  end
-  ret = if exclude(x)
-    f(x, ys...)
-  else
-    walk((xy...,) -> fmap(f, xy...; exclude, walk, cache, prune), x, ys...)
-  end
-  if usecache(cache, x)
-    cache[x] = ret
-  end
-  ret
-end
-
-function _default_walk(f, x, ys...)
-  func, re = functor(x)
-  yfuncs = map(y -> functor(typeof(x), y)[1], ys)
-  re(map(f, func, yfuncs...))
-end
-
 ###
 ### FlexibleFunctors.jl
 ###
diff --git a/src/walks.jl b/src/walks.jl
index d329e4b..63fbcbb 100644
--- a/src/walks.jl
+++ b/src/walks.jl
@@ -88,6 +88,15 @@ end
 
 struct NoKeyword end
 
+usecache(::AbstractDict, x) = isleaf(x) ? anymutable(x) : ismutable(x)
+usecache(::Nothing, x) = false
+
+@generated function anymutable(x::T) where {T}
+  ismutabletype(T) && return true
+  subs =  [:(anymutable(getfield(x, $f))) for f in QuoteNode.(fieldnames(T))]
+  return Expr(:(||), subs...)
+end
+
 """
     CachedWalk(walk[; prune])
 
@@ -109,11 +118,15 @@ CachedWalk(walk; prune = NoKeyword(), cache = IdDict()) =
   CachedWalk(walk, prune, cache)
 
 function (walk::CachedWalk)(recurse, x, ys...)
-  if haskey(walk.cache, x)
+  should_cache = usecache(walk.cache, x)
+  if should_cache && haskey(walk.cache, x)
     return walk.prune isa NoKeyword ? walk.cache[x] : walk.prune
   else
-    walk.cache[x] = walk.walk(recurse, x, ys...)
-    return walk.cache[x]
+    ret = walk.walk(recurse, x, ys...)
+    if should_cache
+      walk.cache[x] = ret
+    end
+    return ret
   end
 end