Add respective frequency units for some time units.

[Aehmlo]

This is part of #30. I went ahead and added the inverse units for the existing (non-metric) time units, but stopped there.

[Aehmlo]

I went ahead and used a as the abbreviation for the year here, following your lead from time.rs.

[iliekturtles]

I believe these conversion factors should be inverted. e.g. 1 cycle per minute = 1.0 / 6.0_E1 Hz. Please double check my math however. If this is the case tests can also be added for Time <-> Frequency.

[Aehmlo]

…I knew something about that seemed off, but I kept convincing myself that "60 Hz is 1 cycle per minute, it's fine." I'll go fix that.

[iliekturtles]

• Change the commit message to include "Resolves Frequency quantity #30." -- I don't think there are any other Frequency units need at this time.
• Additional precision is needed for conversion factors.
• Add tests.

I'll merge once the changes are made!

diff --git a/src/si/frequency.rs b/src/si/frequency.rs                                             
index 134c811..633b2a3 100644                                                                      
--- a/src/si/frequency.rs                                                                          
+++ b/src/si/frequency.rs                                                                          
@@ -36,11 +36,12 @@ quantity! {                                                                    
         @zeptohertz: prefix!(zepto); "zHz", "zeptohertz", "zeptohertz";                           
         @yoctohertz: prefix!(yocto); "yHz", "yoctohertz", "yoctohertz";                           
                                                                                                   
+        @cycles_per_day: 1.157_407_407_407_407_4_E-5; "1/d", "cycle per day", "cycles per day";   
+        @cycles_per_hour: 2.777_777_777_777_777_E-4; "1/h", "cycle per hour", "cycles per hour";  
+        @cycles_per_minute: 1.666_666_666_666_666_6E-2; "1/min", "cycle per minute",              
+            "cycles per minute";                                                                  
         @cycles_per_shake: 1.0_E8; "100 MHz", "cycle per shake", "cycles per shake";              
-        @cycles_per_minute: 1.666_666_E-2; "1/min", "cycle per minute", "cycles per minute";      
-        @cycles_per_hour: 2.777_777_E-4; "1/h", "cycle per hour", "cycles per hour";              
-        @cycles_per_day: 1.157_407_E-5; "1/d", "cycle per day", "cycles per day";                 
-        @cycles_per_year: 3.170_979_E-8; "1/a", "cycle per year", "cycles per year";              
+        @cycles_per_year: 3.170_979_198_376_458_E-8; "1/a", "cycle per year", "cycles per year";  
     }                                                                                             
 }                                                                                                 
                                                                                                   
@@ -82,6 +83,11 @@ mod tests {                                                                     
             test::<t::attosecond, f::exahertz>();                                                 
             test::<t::zeptosecond, f::zettahertz>();                                              
             test::<t::yoctosecond, f::yottahertz>();                                              
+            test::<t::day, f::cycles_per_day>();                                                  
+            test::<t::hour, f::cycles_per_hour>();                                                
+            test::<t::minute, f::cycles_per_minute>();                                            
+            test::<t::shake, f::cycles_per_shake>();                                              
+            test::<t::year, f::cycles_per_year>();                                                
                                                                                                   
             fn test<T: t::Conversion<V>, F: f::Conversion<V>>() {                                 
                 Test::assert_approx_eq(&(V::one() / Time::new::<T>(V::one())),                    

[Aehmlo]

Third time's the charm! I think we should be good now.

One other thing: cycles_per_day doesn't strike me as consistent with e.g. gram or cubic_meter or ampere — namely, it's plural already. I went with this because it was the name suggested at the outset, but do we maybe want to go with e.g. cycle_per_day and update the others to match?

Just a thought.

[iliekturtles]

Good catch. Go ahead and make them singular and then I'll merge.

[iliekturtles]

Merged. Thanks for the PR and sorry for the delay. I just realized that I don't receive a notification when you push new changes to the branch!