Add Base.allunique (#15914)

Allows testing if elements in a collection are distinct (when compared
with isequal). Terminates early in case of repeated elements, has
methods for collections which are by construction distinct. Also added
tests. See discussion at issue #15803.

Author: tpapp

base/exports.jl

@@ -744,6 +744,7 @@ export
 # collections
     all!,
     all,
+    allunique,
     any!,
     any,
     collect,

base/set.jl

@@ -141,6 +141,27 @@ function unique(f::Callable, C)
     out
 end
 
+"""
+    allunique(itr)
+
+Return `true` if all values from `itr` are distinct when compared with `isequal`.
+"""
+function allunique(C)
+    seen = Set{eltype(C)}()
+    for x in C
+        if in(x, seen)
+            return false
+        else
+            push!(seen, x)
+        end
+    end
+    true
+end
+
+allunique(::Set) = true
+
+allunique{T}(r::Range{T}) = (step(r) != zero(T)) || (length(r) <= one(T))
+
 function filter(f, s::Set)
     u = similar(s)
     for x in s

doc/stdlib/collections.rst

@@ -226,6 +226,12 @@ Iterable Collections
 
    Returns an array containing one value from ``itr`` for each unique value produced by ``f`` applied to elements of ``itr``\ .
 
+.. function:: allunique(itr)
+
+   .. Docstring generated from Julia source
+
+   Return ``true`` if all values from ``itr`` are distinct when compared with ``isequal``\ .
+
 .. function:: reduce(op, v0, itr)
 
    .. Docstring generated from Julia source

test/sets.jl

@@ -207,6 +207,20 @@ u = unique([1,1,2])
 @test unique(iseven, [5,1,8,9,3,4,10,7,2,6]) == [5,8]
 @test unique(n->n % 3, [5,1,8,9,3,4,10,7,2,6]) == [5,1,9]
 
+# allunique
+@test allunique([])
+@test allunique(Set())
+@test allunique([1,2,3])
+@test allunique([:a,:b,:c])
+@test allunique(Set([1,2,3]))
+@test !allunique([1,1,2])
+@test !allunique([:a,:b,:c,:a])
+@test allunique(4:7)
+@test allunique(1:1)
+@test allunique(4.0:0.3:7.0)
+@test allunique(4:-1:5)       # empty range
+@test allunique(7:-1:1)       # negative step
+
 # filter
 s = Set([1,2,3,4])
 @test isequal(filter(isodd,s), Set([1,3]))