mentoring continued I hope

Previous Topic Next Topic
 
classic Classic list List threaded Threaded
4 messages Options
Reply | Threaded
Open this post in threaded view
|

mentoring continued I hope

Pharo Smalltalk Users mailing list
Hello,

I have this challenge from exercism :
https://github.com/exercism/pharo-smalltalk/tree/master/exercises/clock

and this function is given :

hour: anInteger minute: anInteger2
     self shouldBeImplemented


Schould I make it on this class method work that the minutes will not
exceed the 59 minutes
So when for example when 70 min are given so hour:0  minute:70 it will
be converted to hour: 1 minutes: 10
or can I better do this on the instance side.

Regards,

Roelof


Reply | Threaded
Open this post in threaded view
|

Re: mentoring continued I hope

Richard Sargent
Administrator
On Sun, Aug 30, 2020 at 10:04 PM Roelof Wobben via Pharo-users <[hidden email]> wrote:
Hello,

I have this challenge from exercism :
https://github.com/exercism/pharo-smalltalk/tree/master/exercises/clock

and this function is given :

hour: anInteger minute: anInteger2
     self shouldBeImplemented


Schould I make it on this class method work that the minutes will not
exceed the 59 minutes
So when for example when 70 min are given so hour:0  minute:70 it will
be converted to hour: 1 minutes: 10

I would argue against that approach. Make it a requirement that a given API must be used with correct values.
e.g. #hours:minutes: requires hours between 00 and 23 and minutes between 00 and 59.

If you want to convert equivalent time values, use a specific API. For example, many time implementations publicly define a seconds-based API, such as Time class>>#fromSeconds:. You can do the same with your implementation with a class-side #fromMinutes: method. (The corresponding instance methods would be #asSeconds and #asMinutes or something similar.)


or can I better do this on the instance side.

Regards,

Roelof


Reply | Threaded
Open this post in threaded view
|

Re: mentoring continued I hope

Richard O'Keefe
In reply to this post by Pharo Smalltalk Users mailing list
I have always found it annoying that the exercism specifications
do not spell things out, so you HAVE to read the tests to find out
what you are supposed to do, which pretty much spoils the point of
them BEING tests.

In this case, we note that there is a test case where the number
of hours is 100, and it is to be accepted as meaning '04'.
There is also a test case where the number of minutes is 160
and it is to be taken as 40 minutes plus 2 hours.

So the only way you can pass the tests is something like
class methods for: 'instance creation'
  hours: h minutes: m
    ^self new setMinutesSinceMidnight: (h * 60 + m bitOr: 0) \\ 1440

methods for: 'private'
  setMinutesSinceMidnight: m
    minutesSinceMidnight := m.

methods for: 'accessing'
  hour
    ^minutesSinceMidnight // 60

  minute
    ^minutesSinceMidnight \\ 60

The only *checking* that is involved is that the hour and minute counts must be integers, which I used " bitOr: 0" to do.  What's the best way to do thisE?

As for where to do checking in general,
put it as close to the encapsulation boundary as you reasonably can.
If there is a PUBLIC method for changing the time on a Clock,
you need to put the checking in that method.  If (as here) a clock value
is supposed to be immutable, put it in the instance creation method.



On Mon, 31 Aug 2020 at 18:18, Roelof Wobben via Pharo-users <[hidden email]> wrote:
Hello,

I have this challenge from exercism :
https://github.com/exercism/pharo-smalltalk/tree/master/exercises/clock

and this function is given :

hour: anInteger minute: anInteger2
     self shouldBeImplemented


Schould I make it on this class method work that the minutes will not
exceed the 59 minutes
So when for example when 70 min are given so hour:0  minute:70 it will
be converted to hour: 1 minutes: 10
or can I better do this on the instance side.

Regards,

Roelof


Reply | Threaded
Open this post in threaded view
|

Re: mentoring continued I hope

Richard O'Keefe
In reply to this post by Richard Sargent
Roelof explicitly said that this is for an Exercism exercise.
That exercise defines the API (implicitly) in the test cases.
Roelof has no choice about what the API is, his job is just
to make the tests pass.  Your ideas about how to design an
API are good ones, it's just that Exercism says what to do.


On Tue, 1 Sep 2020 at 05:01, Richard Sargent <[hidden email]> wrote:
On Sun, Aug 30, 2020 at 10:04 PM Roelof Wobben via Pharo-users <[hidden email]> wrote:
Hello,

I have this challenge from exercism :
https://github.com/exercism/pharo-smalltalk/tree/master/exercises/clock

and this function is given :

hour: anInteger minute: anInteger2
     self shouldBeImplemented


Schould I make it on this class method work that the minutes will not
exceed the 59 minutes
So when for example when 70 min are given so hour:0  minute:70 it will
be converted to hour: 1 minutes: 10

I would argue against that approach. Make it a requirement that a given API must be used with correct values.
e.g. #hours:minutes: requires hours between 00 and 23 and minutes between 00 and 59.

If you want to convert equivalent time values, use a specific API. For example, many time implementations publicly define a seconds-based API, such as Time class>>#fromSeconds:. You can do the same with your implementation with a class-side #fromMinutes: method. (The corresponding instance methods would be #asSeconds and #asMinutes or something similar.)


or can I better do this on the instance side.

Regards,

Roelof