Define monomial constructor (#174)

* Define monomial constructor

* Add tests

Author: blegat

Project.toml

@@ -1,7 +1,7 @@
 name = "DynamicPolynomials"
 uuid = "7c1d4256-1411-5781-91ec-d7bc3513ac07"
 repo = "https://github.com/JuliaAlgebra/DynamicPolynomials.jl.git"
-version = "0.6.2"
+version = "0.6.3"
 
 [deps]
 Future = "9fa8497b-333b-5362-9e8d-4d0656e87820"

src/mono.jl

@@ -30,6 +30,11 @@ function Monomial{V,M}(
     return Monomial{V,M}([vars...], z)
 end
 
+function MP.monomial(vars::Vector{Variable{V,M}}, z::Vector{Int}) where {V,M}
+    @assert issorted(vars, rev = true)
+    return Monomial{V,M}(vars, z)
+end
+
 iscomm(::Type{<:Monomial{V}}) where {V} = iscomm(V)
 Monomial{V,M}() where {V,M} = Monomial{V,M}(Variable{V,M}[], Int[])
 function Monomial(vars::TupOrVec{Variable{V,M}}, z::Vector{Int}) where {V,M}
@@ -79,7 +84,6 @@ MP.exponents(m::Monomial) = m.z
 # /!\ vars not copied, do not mess with vars
 MP.variables(m::Union{Monomial}) = m.vars
 
-MP.monomial(m::Monomial) = m
 # Does m1 divides m2 ?
 #function MP.divides(m1::Monomial, m2::Monomial)
 #    i = j = 1

src/var.jl

@@ -209,6 +209,7 @@ end
 
 MP.monomial(v::Variable) = Monomial(v)
 MP.variables(v::Variable) = [v]
+MP.exponents(v::Variable) = [1]
 MP.ordering(v::Variable) = MP.ordering(typeof(v))
 MP.ordering(::Type{Variable{V,M}}) where {V,M} = M
 

test/runtests.jl

@@ -8,6 +8,15 @@ function alloc_test_lt(f, n)
     @test n >= @allocated f()
 end
 
+# TODO move to MP
+@testset "monomial" begin
+    @polyvar x
+    @test monomial(x) == monomial(variables(x), exponents(x))
+    @polyvar y
+    @test monomial([x, y], [2, 3]) == x^2 * y^3
+    @test_throws AssertionError monomial([y, x], [2, 3]) == x^2 * y^3
+end
+
 # TODO move to MP
 @testset "See https://github.com/jump-dev/SumOfSquares.jl/issues/388" begin
     @polyvar x[1:3]