Added fold

Project.toml

@@ -1,7 +1,7 @@
 name = "PatternFolds"
 uuid = "c18a7f1d-76ad-4ce4-950d-5419b888513b"
 authors = ["Jean-Francois Baffier"]
-version = "0.1.2"
+version = "0.1.3"
 
 [deps]
 Lazy = "50d2b5c4-7a5e-59d5-8109-a42b560f39c0"

src/PatternFolds.jl

@@ -7,9 +7,9 @@ using Lazy
 export PatternFold
 export IVectorFold, VectorFold
 export Interval, IntervalsFold
-export pattern, gap, folds
+export pattern, gap, folds, check_pattern
 export length
-export unfold
+export fold, unfold
 export value
 
 # includes

src/common.jl

@@ -60,3 +60,29 @@ end
 Reset the *unfolded* pattern to the first fold.
 """
 reset_pattern!(mvf) = set_fold!(mvf, 1)
+
+"""
+    fold(v::V, depth = 0)
+returns a suitable `VectorFold`, which when unfolded gives the Vector V.
+"""
+function fold(v::V, depth = 0; kind = :mutable) where {T <: Real, V <: AbstractVector{T}}
+    l = length(v)
+    for i in 1:(l ÷ 2)
+        gap = v[i + 1] - v[1]
+        fold, r = divrem(l, i)
+        if  r == 0 && check_pattern(v, i, gap, fold)
+            # return VectorFold(fold(v[1:i], depth + 1), gap, fold)
+            return make_vector_fold(v[1:i], gap, fold, kind)
+        end
+    end
+    if depth == 0
+        @warn "No non-degenerate patterns have been found" v
+        return make_vector_fold(v, zero(T), 1, kind)
+    else
+        return v
+    end
+end
+
+function make_vector_fold(pattern, gap, fold, kind = :mutable)
+    return make_vector_fold(pattern, gap, fold, Val(kind))
+end

src/immutable_vector.jl

@@ -71,3 +71,17 @@ function Base.iterate(r_iter::Base.Iterators.Reverse{IVectorFold{T,V}},
 
 	return elem, next_state
 end
+
+# Folding a vector to give a suitable VectorFold
+check_pattern(v, w, gap) = all(i -> i == gap, w - v)
+
+function check_pattern(v, i, gap, fold)
+    for j in 1:(fold -1)
+        v_start, v_end = (j - 1) * i + 1, j * i
+        w_start, w_end = j * i + 1, (j + 1) * i
+        !check_pattern(v[v_start:v_end], v[w_start:w_end], gap) && return false
+    end
+    return true
+end
+
+make_vector_fold(pattern, gap, fold, ::Val{:immutable}) = IVectorFold(pattern, gap, fold)

src/vector.jl

@@ -93,3 +93,5 @@ function unfold(mvf::VectorFold; from=1, to=folds(mvf))
     end
     return v
 end
+
+make_vector_fold(pattern, gap, fold, ::Val{:mutable}) = VectorFold(pattern, gap, fold)

test/vector.jl

@@ -31,4 +31,16 @@
     end
     @test isempty(IVectorFold(Vector(),1,1))
     @test isempty(VectorFold(Vector(),1,1))
+
+    v1 = VectorFold([42,3,45,6],13,4)
+    w1 = unfold(v1)
+    v11 = fold(w1)
+
+    @test unfold(v11) == w1
+
+    v2 = VectorFold([34,34,43,43],10,3)
+    w2 = unfold(v2)
+    v22 = fold(w2)
+
+    @test unfold(v22) == w2
 end