Fix #748: better error message for signarea

JuliaGeometry · Feb 13, 2024 · d9d3bd9 · d9d3bd9
1 parent 3a9e8d5
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diff --git a/src/polytopes/ngon.jl b/src/polytopes/ngon.jl
@@ -67,6 +67,8 @@ function signarea(t::Triangle{2})
   signarea(v[1], v[2], v[3])
 end
 
+signarea(::Triangle{3}) = error("signed area only defined for triangles embedded in R², use `area` instead")
+
 function normal(t::Triangle{3})
   A, B, C = t.vertices
   ((B - A) × (C - A)) / 2

diff --git a/test/polytopes.jl b/test/polytopes.jl
@@ -378,6 +378,9 @@
     t = Triangle(P3(0, 0, 0), P3(1, 0, 0), P3(0, 1, 0))
     @test isconvex(t)
 
+    t = Triangle(P3(0, 0, 0), P3(1, 0, 0), P3(0, 1, 0))
+    @test_throws ErrorException("signed area only defined for triangles embedded in R², use `area` instead") signarea(t)
+
     t = Triangle(P2(0, 0), P2(1, 0), P2(0, 1))
     @test sprint(show, t) == "Triangle((0.0, 0.0), (1.0, 0.0), (0.0, 1.0))"
     if T === Float32