lazy broadcasting for Frequencies

Author: jishnub

src/definitions.jl

@@ -415,6 +415,12 @@ Base.step(x::Frequencies) = x.multiplier
 
 Base.copy(x::Frequencies) = x
 
+# Retain the lazy representation upon scalar multiplication
+Broadcast.broadcasted(::Base.Broadcast.DefaultArrayStyle{1}, ::typeof(*), f::Frequencies, x::Number) =
+    Frequencies(f.n_nonnegative, f.n, f.multiplier * x)
+Broadcast.broadcasted(s::Base.Broadcast.DefaultArrayStyle{1}, ::typeof(*), x::Number, f::Frequencies) =
+    Broadcast.broadcasted(s, *, f, x)
+
 """
     fftfreq(n, fs=1)
 Return the discrete Fourier transform (DFT) sample frequencies for a DFT of length `n`. The returned

test/runtests.jl

@@ -101,6 +101,13 @@ end
     @test eltype(fftfreq(5, ComplexF64(2))) == ComplexF64
 
     @test_throws ArgumentError Frequencies(12, 10, 1)
+
+    @testset "scaling" begin
+        @test fftfreq(4, 1) * 2 === fftfreq(4, 2)
+        @test fftfreq(4, 1) .* 2 === fftfreq(4, 2)
+        @test 2 * fftfreq(4, 1) === fftfreq(4, 2)
+        @test 2 .* fftfreq(4, 1) === fftfreq(4, 2)
+    end
 end
 
 @testset "normalization" begin