From 626fcd1beebf472487f11cd588661e2d5303de7d Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Stefanos=20Carlstr=C3=B6m?= <jagot@users.noreply.github.com>
Date: Wed, 6 Oct 2021 13:13:27 +0200
Subject: [PATCH] Fix span for sum of disjoint fields (#17)

* Fix timeaxis for zero-length intervals

* Fix span for sum of disjoint fields

* Bump version
---
 Project.toml        | 2 +-
 src/arithmetic.jl   | 6 +++++-
 src/time_axis.jl    | 7 ++++---
 test/arithmetic.jl  | 3 +++
 test/field_types.jl | 7 +++++++
 5 files changed, 20 insertions(+), 5 deletions(-)

diff --git a/Project.toml b/Project.toml
index fee9185..cd763e3 100644
--- a/Project.toml
+++ b/Project.toml
@@ -1,7 +1,7 @@
 name = "ElectricFields"
 uuid = "2f84ce32-9bb1-11e8-0d9f-3dce90a4beca"
 authors = ["Stefanos Carlström <stefanos.carlstrom@gmail.com>"]
-version = "0.1.3"
+version = "0.1.4"
 
 [deps]
 FFTW = "7a1cc6ca-52ef-59f5-83cd-3a7055c09341"
diff --git a/src/arithmetic.jl b/src/arithmetic.jl
index 3133025..bf19cee 100644
--- a/src/arithmetic.jl
+++ b/src/arithmetic.jl
@@ -112,7 +112,11 @@ vector_potential(f::SumField, t::Number) =
 
 polarization(f::SumField) = polarization(f.a)
 
-span(f::SumField) = span(f.a) ∪ span(f.b)
+function span(f::SumField)
+    sa = span(f.a)
+    sb = span(f.b)
+    min(sa.left,sb.left)..max(sa.right,sb.right)
+end
 steps(f::SumField, ndt::Int) = steps(f, ndt/min(austrip.(period.((f.a,f.b)))...))
 
 for fun in [:wavelength, :period, :frequency, :wavenumber, :fundamental, :photon_energy]
diff --git a/src/time_axis.jl b/src/time_axis.jl
index d767c09..3e94059 100644
--- a/src/time_axis.jl
+++ b/src/time_axis.jl
@@ -35,13 +35,14 @@ frequency `fs`.
 """
 function timeaxis(f::AbstractField, fs::Number=default_sampling_frequency(f))
     num_steps = steps(f, fs)
-    if num_steps > 1
-        range(span(f), length=num_steps)
+    s = span(f)
+    if num_steps > 1 || s.left == s.right
+        range(s, length=num_steps)
     else
         # This hack is mainly useful for calculations where exactly
         # one time step should be taken, (b-a) becomes the step
         # length.
-        a,b = endpoints(span(f))
+        a,b = endpoints(s)
         a:(b-a):a
     end
 end
diff --git a/test/arithmetic.jl b/test/arithmetic.jl
index 3e87efa..93c8f96 100644
--- a/test/arithmetic.jl
+++ b/test/arithmetic.jl
@@ -141,6 +141,9 @@
         Z = X + delay(Y, 3/2π)
 
         @test field_amplitude(Z, 4.0) ≈ field_amplitude(X, 4.0) + field_amplitude(Y, 4.0 - 3/2π)
+
+        W = X + delay(Y, 35.0)
+        @test span(W) == span(X).left..(span(Y).right+35.0)
     end
 
     @testset "Padded fields" begin
diff --git a/test/field_types.jl b/test/field_types.jl
index caee877..80e6d25 100644
--- a/test/field_types.jl
+++ b/test/field_types.jl
@@ -165,6 +165,13 @@
         @test photon_energy(F) == 2π
 
         @test dimensions(F) == 1
+
+        @field(Fzero) do
+            I₀ = 4.0
+            tmax = 0.0
+            kind = :constant
+        end
+        @test timeaxis(Fzero) == range(0, stop=0, length=0)
     end
 
     @testset "Ramps" begin