use 64-bit precision for nanoseconds_per_sample (#50)

Project.toml

@@ -1,7 +1,7 @@
 name = "TimeSpans"
 uuid = "bb34ddd2-327f-4c4a-bfb0-c98fc494ece1"
 authors = ["Beacon Biosignals, Inc."]
-version = "0.3.4"
+version = "0.3.5"
 
 [deps]
 Dates = "ade2ca70-3891-5945-98fb-dc099432e06a"

src/TimeSpans.jl

@@ -186,8 +186,11 @@ duration(span) = stop(span) - start(span)
     TimeSpans.nanoseconds_per_sample(sample_rate)
 
 Given `sample_rate` in Hz, return the number of nanoseconds corresponding to one sample.
+
+Note that this function performs the relevant calculation using `Float64(sample_rate)`
+in order to improve the accuracy of the result.
 """
-nanoseconds_per_sample(sample_rate) = inv(sample_rate) * NS_IN_SEC
+nanoseconds_per_sample(sample_rate) = NS_IN_SEC / Float64(sample_rate)
 
 """
     index_from_time(sample_rate, sample_time::Period)

test/runtests.jl

@@ -125,16 +125,7 @@ end
             @test index == index_from_time(Float64(rate), sample_time)
         end
     end
-end
-
-@testset "`in` and `findall`" begin
-    @test findall(in(TimeSpan(1, 10)), Nanosecond.(5:15)) == 1:5
-    @test findall(in(TimeSpan(1, 10)), map(Nanosecond, (9,10,11))) == 1:1
-    @test in(TimeSpan(1,2))(Nanosecond(1))
-    @test !in(TimeSpan(1,2))(Nanosecond(2))
-end
 
-@testset "index_from_time" begin
     @testset "docstring" begin
         @test index_from_time(1, Second(0)) == 1
         @test index_from_time(1, Second(1)) == 2
@@ -147,13 +138,22 @@ end
         @test index_from_time(200, ns) == 30001
         @test index_from_time(200e0, ns) == 30001
         @test index_from_time(200f0, ns) == 30001
+        @test time_from_index(143.5, 8611) == Nanosecond(60000000000)
+        @test time_from_index(Float32(143.5), 8611) == Nanosecond(60000000000)
     end
 
     for i in 1:10
         @test index_from_time(1.5, time_from_index(1.5, 1:i)) == 1:i
     end
 end
 
+@testset "`in` and `findall`" begin
+    @test findall(in(TimeSpan(1, 10)), Nanosecond.(5:15)) == 1:5
+    @test findall(in(TimeSpan(1, 10)), map(Nanosecond, (9,10,11))) == 1:1
+    @test in(TimeSpan(1,2))(Nanosecond(1))
+    @test !in(TimeSpan(1,2))(Nanosecond(2))
+end
+
 @testset "merge_spans!" begin
     spans = [TimeSpan(0, 10), TimeSpan(6, 12), TimeSpan(15, 20),
              TimeSpan(21, 30), TimeSpan(29, 31)]