adding sparse to/from cycle and list

src/PermPlain.jl

@@ -1,7 +1,7 @@
 module PermPlain
 
 using DataStructures.counter
-import Base: isperm
+import Base: isperm, randperm
 
 # Permutations implemented without defining new types.
 # The types, PermList, PermCycs, use this code.
@@ -18,6 +18,8 @@ export permcycles, cyclelengths, permsgn, permorder,
  cyc_pow_perm, permcommute, permdistance, permordercyc,
  ltpermlist
 
+randperm{T<:Real}(::Type{T}, n::Integer) = collect(T,randperm(n))
+
 # Get the lengths of the cycles in cyclic decomposition
 # from input permutation list (PLIST).
 # Store only the lengths of the cycles, not the cycles
@@ -479,6 +481,85 @@ function fixed{T<:Real}(p::AbstractVector{T})
  return fixedel
 end
 
+function listtosparse{T<:Real}(p::AbstractVector{T})
+ data = Dict{T,T}()
+ maxk = zero(T)
+ for i in p
+ pv = p[i]
+ if pv != i
+ data[i] = pv
+ pv > maxk ? maxk = pv : nothing
+ end
+ end
+ return (data,maxk)
+end
+
+function cycstosparse{T<:Real}(cycs::AbstractArray{Array{T,1},1})
+ data = Dict{T,T}()
+ maxk = zero(T)
+ for c in cycs
+ data[c[1]] = c[end]
+# println(" *** doing ", c[end], " ", c[1])
+ for i in 2:length(c)
+# println("doing ", c[i], " ", c[i-1])
+ pv = c[i]
+ pv > maxk ? maxk = pv : nothing
+ data[pv] = c[i-1]
+ end
+ end
+ return (data,maxk)
+end
+
+function sparsetolist{T}(sp::Dict{T,T})
+ p = [one(T):convert(T,maximum(sp)[1])]
+ for (i,v) in sp
+ p[v] = i
+ end
+ return p
+end
+
+function sparsetocycles{T}(sp::Dict{T,T})
+ cycs = Array(Array{T,1},0)
+# ks = collect(values(sp))
+ ks = collect(keys(sp))
+ n = length(ks)
+ seen = Dict{T,Bool}()
+ for k in ks seen[k] = false end
+ k = ks[1]
+ nseen = 0
+ while nseen <= n
+ didsee = false
+ for i in ks
+ if seen[i] == false
+ k = i
+ didsee = true
+ break
+ end
+ end
+ didsee == false ? (push!(cycs,cyc); break) : nothing
+ k1 = k
+ cyc = Array(T,0)
+# push!(cyc,k)
+# println(" out pushing $k") 
+ nseen = nseen + 1
+ while true
+ push!(cyc,k)
+# println(" 1 in pushing $k") 
+ seen[k] = true
+ k = sp[k]
+ nseen = nseen + 1
+ if k == k1
+ break
+ end
+# println(" 2 in pushing $k")
+# push!(cyc,k)
+ end
+ push!(cycs,reverse!(cyc))
+ end
+ return cycs
+end
+
+
 ## Output ##
 
 function cycleprint(io::IO, v::Array)