don't hijack Base-level methods

Author: Shashi Gowda

Diff for: src/array/map-reduce.jl

@@ -24,7 +24,7 @@ function stage(ctx, node::Map)
     Cat(Any, domain(primary), domainchunks(primary), thunks)
 end
 
-map(f, xs::LazyArray...) = Map(f, xs)
+map(f, x::LazyArray, xs::LazyArray...) = Map(f, (x, xs...))
 map(f, x::AbstractChunk) = map(f, Computed(x))
 
 #### Reduce

Diff for: src/array/matrix.jl

@@ -292,10 +292,10 @@ function size(c::Concat)
     (sz...,)
 end
 
-function cat(idx::Int, ds::ArrayDomain...)
-    h = (ds[1])
+function cat(idx::Int, d::ArrayDomain, ds::ArrayDomain...)
+    h = (d)
     out_idxs = [x for x in indexes(h)]
-    len = sum(map(x->length(indexes(x)[idx]), ds))
+    len = sum(map(x->length(indexes(x)[idx]), (d, ds...)))
     fst = first(out_idxs[idx])
     out_idxs[idx] = fst:(fst+len-1)
     ArrayDomain(out_idxs)