From 0ca0d4a3ebf7f0671571186bde4f884eb7de1618 Mon Sep 17 00:00:00 2001
From: mforets <mforets@gmail.com>
Date: Sun, 3 Jan 2021 22:30:57 -0300
Subject: [PATCH] promote type in polyhedron support function

---
 src/Interfaces/AbstractPolyhedron_functions.jl |  5 +++++
 src/Sets/HPolyhedron.jl                        | 18 ++++++++++--------
 2 files changed, 15 insertions(+), 8 deletions(-)

diff --git a/src/Interfaces/AbstractPolyhedron_functions.jl b/src/Interfaces/AbstractPolyhedron_functions.jl
index df006f4b6b..bbc0c1797d 100644
--- a/src/Interfaces/AbstractPolyhedron_functions.jl
+++ b/src/Interfaces/AbstractPolyhedron_functions.jl
@@ -19,6 +19,11 @@ function default_lp_solver(N::Type{<:Rational})
     GLPKSolverLP(method=:Exact)
 end
 
+# helper function given two possibly different numeric types
+function default_lp_solver(M::Type{<:Number}, N::Type{<:Number})
+    return default_lp_solver(promote_type(M, N))
+end
+
 # Polyhedra backend (fallback method)
 function default_polyhedra_backend(P, N)
     require(:Polyhedra; fun_name="default_polyhedra_backend")
diff --git a/src/Sets/HPolyhedron.jl b/src/Sets/HPolyhedron.jl
index a1e3a70802..c87acb4952 100644
--- a/src/Sets/HPolyhedron.jl
+++ b/src/Sets/HPolyhedron.jl
@@ -80,7 +80,8 @@ function dim(P::HPoly)
 end
 
 """
-    ρ(d::AbstractVector{N}, P::HPoly{N}; solver=default_lp_solver(N)) where {N}
+    ρ(d::AbstractVector{M}, P::HPoly{N};
+      solver=default_lp_solver(M, N)) where {M, N}
 
 Evaluate the support function of a polyhedron (in H-representation) in a given
 direction.
@@ -89,7 +90,7 @@ direction.
 
 - `d`      -- direction
 - `P`      -- polyhedron in H-representation
-- `solver` -- (optional, default: `default_lp_solver(N)`) the backend used to
+- `solver` -- (optional, default: `default_lp_solver(M, N)`) the backend used to
               solve the linear program
 
 ### Output
@@ -98,8 +99,8 @@ The support function of the polyhedron.
 If a polytope is unbounded in the given direction, we throw an error.
 If a polyhedron is unbounded in the given direction, the result is `Inf`.
 """
-function ρ(d::AbstractVector{N}, P::HPoly{N};
-           solver=default_lp_solver(N)) where {N}
+function ρ(d::AbstractVector{M}, P::HPoly{N};
+           solver=default_lp_solver(M, N)) where {M, N}
     lp, unbounded = σ_helper(d, P, solver)
     if unbounded
         if P isa HPolytope
@@ -112,7 +113,8 @@ function ρ(d::AbstractVector{N}, P::HPoly{N};
 end
 
 """
-    σ(d::AbstractVector{N}, P::HPoly{N}; solver=default_lp_solver(N)) where {N}
+    σ(d::AbstractVector{M}, P::HPoly{N};
+      solver=default_lp_solver(M, N) where {M, N}
 
 Return the support vector of a polyhedron (in H-representation) in a given
 direction.
@@ -121,15 +123,15 @@ direction.
 
 - `d`      -- direction
 - `P`      -- polyhedron in H-representation
-- `solver` -- (optional, default: `default_lp_solver(N)`) the backend used to
+- `solver` -- (optional, default: `default_lp_solver(M, N)`) the backend used to
               solve the linear program
 
 ### Output
 
 The support vector in the given direction.
 """
-function σ(d::AbstractVector{N}, P::HPoly{N};
-           solver=default_lp_solver(N)) where {N}
+function σ(d::AbstractVector{M}, P::HPoly{N};
+           solver=default_lp_solver(M, N)) where {M, N}
     lp, unbounded = σ_helper(d, P, solver)
     if unbounded
         if P isa HPolytope