DateTime, DayOfWeek in range comparison

Urs Enzler

We solved a similar problem by using a mapping from DayOfWeek to integer that returned 7 instead of 0 for Sunday. This way your code would work, too. Not very nice but it works. For .net the week start on Sunday :(

-^-^-^-^-^-^-^- no risk no funk

buchstaben

This will fix the problem for Saturday-Sunday, but it will not solve for Saturday-Tuesday.

Spacix One

why not:

protected override bool checkTimepoint(DateTime timepoint, DayOfWeek from, DayOfWeek to)
{
return timepoint.DayOfWeek >= from && timepoint.DayOfWeek <= to;
}

:)

-Spacix All your skynet questions[^] belong to solved

I dislike the black-and-white voting system on questions/answers. X|

buchstaben

because this doesn't work. testcase: timepoint = new DateTime(2008,5,4);//sunday, 0 from = DayOfWeek.Friday; // 5 to = DayOfWeek.Tuesday; // 2 return 0 >= 5 && 0 <= 2; return value is 'false', but sunday is between friday and tuesday!

realJSOP

You can use the CultureInfo class to set the first day of the week.

using System.Threading;

Thread.CurrentThread.CurrentCulture.DateTimeFormat.FirstDayOfWeek = DayOfWeek.Sunday;

So, set the first day of the week to whatever day you want, and then do your comparison.

protected override bool checkTimepoint(DateTime timepoint, DayOfWeek from, DayOfWeek to)
{
Thread.CurrentThread.CurrentCulture.DateTimeFormat.FirstDayOfWeek = from;
bool inRange = timepoint.DayOfWeek >= from && timepoint.DayOfWeek <= to;
Thread.CurrentThread.CurrentCulture.DateTimeFormat.FirstDayOfWeek = DayOfWeek.Sunday;
return inRange;
}

"Why don't you tie a kerosene-soaked rag around your ankles so the ants won't climb up and eat your candy ass..." - Dale Earnhardt, 1997
-----
"...the staggering layers of obscenity in your statement make it a work of art on so many levels." - Jason Jystad, 10/26/2001

modified on Friday, May 2, 2008 1:26 PM

PIEBALDconsult

return ( true ) ; Every timepoint falls between some DayOfWeek X and some DayOfWeek Y. :-D

buchstaben wrote:

Thursday-Wednesday

Did you mean that? If you want Sunday to sort higher than Saturday, then you can simply add seven to it, but you'll need to store the values as integers rather than as the provided enum values.

int x = (int) timepoint.DayOfWeek ;
int y = (int) from ;
int z = (int) to ;

x += x==0 ? 7 : 0 ;
y += y==0 ? 7 : 0 ;
z += z==0 ? 7 : 0 ;

return ( x >= y && x <= z ) ;

but that's rather ugly.

PIEBALDconsult · modified on Friday, May 2, 2008 1:26 PM

Huh, interesting. I wonder how it performs in a loop.

realJSOP

You can set the first day of the week to be thursday, and then the comparison would work.

"Why don't you tie a kerosene-soaked rag around your ankles so the ants won't climb up and eat your candy ass..." - Dale Earnhardt, 1997
-----
"...the staggering layers of obscenity in your statement make it a work of art on so many levels." - Jason Jystad, 10/26/2001

realJSOP

If performance is an issue (in a loop), you could always wait until the loop is done and reset to the proper 1st day at that point, thus saving n calls to do it in that checkpoint function.

"Why don't you tie a kerosene-soaked rag around your ankles so the ants won't climb up and eat your candy ass..." - Dale Earnhardt, 1997
-----
"...the staggering layers of obscenity in your statement make it a work of art on so many levels." - Jason Jystad, 10/26/2001

realJSOP

Ignore my first post. This is the best way (notice no bizarre culture crap going on):

DayOfWeek from = DayOfWeek.Thursday;
DayOfWeek to = DayOfWeek.Tuesday;

DayOfWeek currentDay = DayOfWeek.Wednesday;

bool inRange = (currentDay >= from || currentDay <= to);

Notice that I'm using OR instead of AND. If you make currentDay Wednesday, inRange will be false. If you make it any other day, it will be true. It's kind of pointless to do a Sunday-Saturday (or similar) comparison because any date will fall into the range. BTW, the comparison above also works for from=Saturday and to=Sunday.

"Why don't you tie a kerosene-soaked rag around your ankles so the ants won't climb up and eat your candy ass..." - Dale Earnhardt, 1997
-----
"...the staggering layers of obscenity in your statement make it a work of art on so many levels." - Jason Jystad, 10/26/2001

realJSOP

Just thought I'd let you know I was completely wrong. :) I posted a new response to the OP with the correct solution.

"Why don't you tie a kerosene-soaked rag around your ankles so the ants won't climb up and eat your candy ass..." - Dale Earnhardt, 1997
-----
"...the staggering layers of obscenity in your statement make it a work of art on so many levels." - Jason Jystad, 10/26/2001

PIEBALDconsult

What? Say it ain't so! :omg:

PIEBALDconsult

I was just reviewing a method I wrote a few months back where I was checking to see if a value (integer) is between two others. I decided I needed more than a true/false, there are (currently) four result values:

    \[System.FlagsAttribute()\]
    public enum CheckRangeResult
    {
        WithinStrictRange = 0
    ,
        Low               = 1
    ,
        High              = 2
    ,
        WithinLooseRange  = 3
    }

Basically; given Min, Max, and Test we expect Min to be less than Max; and Test will be Lower than Min (1), Higher than Max (2), or WithinStrictRange (0). But, when Min is greater than Max and Test is between Min and Max, both tests are true, yielding WithinLooseRange (3). In the case presented here, when Min is greater than Max and Test is not between the values, that should translate to "true", but that's not currently supported. I think I need to add value 4 to indicate that Min is greater than Max, then WithinLooseRange would have value 7. I'll think about it over the weekend.

PIEBALDconsult

It occurred to me late today that this might make a good Friday Programming Quiz. :-D

realJSOP

Maybe even two questions... 1) Given the following:

DayOfWeek startDay = DayOfWeek.Thursday;
DayOfWeek endDay = DayOfWeek.Monday;
DayOfWeek currentDay = DayOfWeek.Wednesday;

Write a C# publicly accessible function that determines whether or not the day falls between startDay and endDay. The function should work for any combination of startDay/endDay values, and should return a boolean value (true if in range, false if not in range). Answer:

public bool DateInRange(DayOfWeek currentDay, DayOfWeek startDay, DayofWeek endDay)
{
return (currentDay >= startDay || currentDay <= endDay);
}

Given the function above, change the function so that the class encapsulating it does not have to be instantiated in order to use the function. Answer:

public static bool DateInRange(DayOfWeek currentDay, DayOfWeek startDay, DayofWeek endDay)
{
return (currentDay >= startDay || currentDay <= endDay);
}

"Why don't you tie a kerosene-soaked rag around your ankles so the ants won't climb up and eat your candy ass..." - Dale Earnhardt, 1997
-----
"...the staggering layers of obscenity in your statement make it a work of art on so many levels." - Jason Jystad, 10/26/2001

PIEBALDconsult

I don't think that works with the "normal" case where startDay < endDay. It's also not a very general solution (which is no crime). Given a number (value) line, two points on that line that define a range, and another point to test inclusion. Normal ........... 1 > 2 < 3 Inverted (endponts not in normal order) ........... 4 < 5 > 6 The test value could be in any of the spots labeled 1 - 6. We then need to assign true/false to these spots. Clearly 2 yields true, while 1 and 3 yield false. The question is about the inverted range; The OP needs to assign true to 4 and 6, false to 5. The code I wrote in November was designed to allow assigning true to 5, false to 4 and 6. I have now modified my helper method (and enum) so it returns one of six values (it was four previously). The application then needs to provide a method that handles the translation to true/false.

realJSOP

I think this should cover it then... :)

public static void DayInRange(DayOfWeek currentDay, DayOfWeek startDay, DayOfWeek endDay)
{
if (startDay == endDay)
{
return true;
}
if (startDay < endDay)
{
return (currentDay >= startDay && currentDay <= endDay);
}
return (currentDay >= startDay || currentDay <= endDay);
}

"Why don't you tie a kerosene-soaked rag around your ankles so the ants won't climb up and eat your candy ass..." - Dale Earnhardt, 1997
-----
"...the staggering layers of obscenity in your statement make it a work of art on so many levels." - Jason Jystad, 10/26/2001

PIEBALDconsult

That hurts my eyes. (Not that I should talk. :-O )