no longer require Requires

Project.toml

@@ -9,14 +9,15 @@ Hypatia = "b99e6be6-89ff-11e8-14f8-45c827f4f8f2"
 JuMP = "4076af6c-e467-56ae-b986-b466b2749572"
 LinearAlgebra = "37e2e46d-f89d-539d-b4ee-838fcccc9c8e"
 Nemo = "2edaba10-b0f1-5616-af89-8c11ac63239a"
-Requires = "ae029012-a4dd-5104-9daa-d747884805df"
 SparseArrays = "2f01184e-e22b-5df5-ae63-d93ebab69eaf"
 
 [weakdeps]
 CyclotomicNumbers = "c380f8b6-65b3-4789-a31b-7d6b5dc6d4c5"
+MATLAB = "10e44e05-a98a-55b3-a45b-ba969058deb6"
 
 [extensions]
 KetExact = "CyclotomicNumbers"
+KetMATLAB = "MATLAB"
 
 [compat]
 Combinatorics = "1"
@@ -29,7 +30,6 @@ LinearAlgebra = "1"
 Nemo = "0.39 - 0.46"
 Quadmath = "0.5.10"
 Random = "1"
-Requires = "1"
 SparseArrays = "1"
 Test = "1"
 julia = "1.9"

ext/KetMATLAB/KetMATLAB.jl

@@ -0,0 +1,12 @@
+module KetMATLAB
+
+import Ket
+import MATLAB
+
+function Ket.tsirelson_bound(CG::Matrix{<:Real}, scenario::Vector{<:Integer}, level::Integer)
+    CG = Float64.(CG)
+    scenario = Float64.(scenario)
+    return MATLAB.mxcall(:mtk_tsirelson, 1, CG, scenario, level)
+end
+
+end # module

src/Ket.jl

@@ -21,9 +21,4 @@ include("multilinear.jl")
 include("supermaps.jl")
 include("entanglement.jl")
 
-import Requires
-function __init__()
-    Requires.@require MATLAB = "10e44e05-a98a-55b3-a45b-ba969058deb6" include("TsirelsonBoundMATLAB.jl")
-end
-
 end # module Ket

src/nonlocal.jl

@@ -102,6 +102,20 @@ function _update_odometer!(ind::AbstractVector{<:Integer}, upper_lim::Integer)
     end
 end
 
+"""
+    tsirelson_bound(CG::Matrix, scenario::Vector, level::Integer)
+
+Upper bounds the Tsirelson bound of a bipartite Bell funcional game `CG`, written in Collins-Gisin notation.
+`scenario` is vector detailing the number of inputs and outputs, in the order [oa, ob, ia, ib].
+`level` is an integer determining the level of the NPA hierarchy.
+
+This function requires [Moment](https://github.com/ajpgarner/moment). It is only available if you first do "import MATLAB" or "using MATLAB".
+"""
+function tsirelson_bound(CG, scenario, level)
+    error("This function requires MATLAB. Do `import matlab` or `using MATLAB` in order to enable it.")
+end
+export tsirelson_bound
+
 """
     fp2cg(V::Array{T,4}) where {T <: Real}