Add cumsum and cumprod methods (#2)

* Add cumsum and cumprod methods

* test for cumsum and cumprod

* cumsum and cumprod docs

Author: jebej

docs/src/index.md

@@ -40,7 +40,9 @@ TupleTools.vcat
 ```
 ```@docs
 TupleTools.sum
+TupleTools.cumsum
 TupleTools.prod
+TupleTools.cumprod
 ```
 
 ```@docs

src/TupleTools.jl

@@ -3,6 +3,7 @@ module TupleTools
 
 using Base: tuple_type_head, tuple_type_tail, tuple_type_cons, tail, front, setindex
 # import Base: permute # TODO: this can disappear when Sparse moves out of Base
+import Base: cumsum, cumprod
 
 """
     struct StaticLength{N} end
@@ -114,6 +115,18 @@ Returns the sum of the element of a tuple, or `0` for an empty tuple.
 @inline sum(t::Tuple{Any}) = t[1]
 @inline sum(t::Tuple) = t[1]+sum(tail(t))
 
+"""
+    cumsum(t::Tuple)
+
+Returns the cumulative sum of the elements of a tuple, or `()` for an empty tuple.
+"""
+function cumsum(t::Tuple)
+    t_1, t_tail = first(t), tail(t)
+    return (t_1,cumsum((t_1+first(t_tail),tail(t_tail)...))...)
+end
+cumsum(t::Tuple{Any}) = t
+cumsum(t::Tuple{}) = t
+
 """
     prod(t::Tuple)
 
@@ -123,6 +136,18 @@ Returns the product of the elements of a tuple, or `1` for an empty tuple.
 @inline prod(t::Tuple{Any}) = t[1]
 @inline prod(t::Tuple) = t[1]*prod(tail(t))
 
+"""
+    cumprod(t::Tuple)
+
+Returns the cumulative product of the elements of a tuple, or `()` for an empty tuple.
+"""
+function cumprod(t::Tuple)
+    t_1, t_tail = first(t), tail(t)
+    return (t_1,cumprod((t_1*first(t_tail),tail(t_tail)...))...)
+end
+cumprod(t::Tuple{Any}) = t
+cumprod(t::Tuple{}) = t
+
 """
     minimum(t::Tuple)
 

test/runtests.jl

@@ -36,7 +36,9 @@ i = rand(1:n)
 @test @inferred(TupleTools.vcat((1,2,3),4,(5,),(),(6,7,8))) == (1,2,3,4,5,6,7,8)
 
 @test @inferred(TupleTools.sum(t)) == sum(t)
+@test @inferred(TupleTools.cumsum(t)) == (cumsum(p)...,)
 @test @inferred(TupleTools.prod(t)) == prod(t)
+@test @inferred(TupleTools.cumprod(t)) == (cumprod(p)...,)
 
 @test @inferred(TupleTools.findmin(t)) == findmin(t)
 @test @inferred(TupleTools.findmax(t)) == findmax(t)