Hi,

I would simply like to get someone's age, but I am a little lost with time and date functions. I can already get the duration, but after reading the documentation it's unclear to me how to convert that into years. See following code:

import std.stdio;

void getAge(int yyyy, int mm, int dd) {
  import std.datetime;
  SysTime t1 = SysTime(Date(yyyy, mm, dd));
  SysTime t2 = Clock.currTime();
  writeln(t2 - t1);
}

int main() {
  try
    getAge(1980, 1, 1);
  catch(Exception e) {
    writefln("%s.\n(%s, line %s)", e.msg, e.file, e.line);
  }
}

Notice getAge should return ubyte instead of void, only I haven't been able to find how to do it. Any suggestion would be welcome.

Thanks in advance.

On Sunday, 15 January 2017 at 03:43:32 UTC, Nestor wrote:
> Hi,
>
> I would simply like to get someone's age, but I am a little lost with time and date functions. I can already get the duration, but after reading the documentation it's unclear to me how to convert that into years. See following code:
>
> import std.stdio;
>
> void getAge(int yyyy, int mm, int dd) {
>   import std.datetime;
>   SysTime t1 = SysTime(Date(yyyy, mm, dd));
>   SysTime t2 = Clock.currTime();
>   writeln(t2 - t1);
> }
>
> int main() {
>   try
>     getAge(1980, 1, 1);
>   catch(Exception e) {
>     writefln("%s.\n(%s, line %s)", e.msg, e.file, e.line);
>   }
> }
>
> Notice getAge should return ubyte instead of void, only I haven't been able to find how to do it. Any suggestion would be welcome.
>
> Thanks in advance.

Does this do what you want?
import std.stdio;

uint getAge(int yyyy, int mm, int dd) {
  import std.datetime;
  SysTime t1 = SysTime(Date(yyyy, mm, dd));
  SysTime t2 = Clock.currTime();
  return( (t2.year - t1.year));
}

void main() {
  auto age = getAge(1980, 1, 1);
  writefln("age is %s", age);
}

On Sunday, 15 January 2017 at 06:23:56 UTC, Dave Chapman wrote:
> Does this do what you want?
> import std.stdio;
>
> uint getAge(int yyyy, int mm, int dd) {
>   import std.datetime;
>   SysTime t1 = SysTime(Date(yyyy, mm, dd));
>   SysTime t2 = Clock.currTime();
>   return( (t2.year - t1.year));
> }
>
> void main() {
>   auto age = getAge(1980, 1, 1);
>   writefln("age is %s", age);
> }

It seems to work, but not very accurately, see variation:

import std.stdio;

uint getAge() {
  import std.datetime;
  SysTime t1 = SysTime(Date(2000, 12, 31));
  SysTime t2 = SysTime(Date(2001, 1, 1));
  return((t2.year - t1.year));
}

void main() {
  auto age = getAge();
  writefln("age is %s", age);
}


I eventually came up with this, but it seems an ugly hack:

import std.stdio;

uint getAge(int yyyy, ubyte mm, ubyte dd) {
  ubyte correction;
  import std.datetime;
  SysTime t = Clock.currTime();
  if (t.month < mm) correction = 1;
  else if (t.month == mm) correction = (t.day < dd) ? 1 : 0;
  else correction = 0;
  return (t.year - yyyy - correction);
}

void main() {
  try
    writefln("Edad: %s años.", getAge(1958, 1, 21));
  catch(Exception e) {
    writefln("%s.\n(%s, line %s)", e.msg, e.file, e.line);
  }
}

Isn't there a built-in function to do this?

On 15/01/2017 4:43 PM, Nestor wrote:
> Hi,
>
> I would simply like to get someone's age, but I am a little lost with
> time and date functions. I can already get the duration, but after
> reading the documentation it's unclear to me how to convert that into
> years. See following code:
>
> import std.stdio;
>
> void getAge(int yyyy, int mm, int dd) {
>   import std.datetime;
>   SysTime t1 = SysTime(Date(yyyy, mm, dd));
>   SysTime t2 = Clock.currTime();
>   writeln(t2 - t1);
> }
>
> int main() {
>   try
>     getAge(1980, 1, 1);
>   catch(Exception e) {
>     writefln("%s.\n(%s, line %s)", e.msg, e.file, e.line);
>   }
> }
>
> Notice getAge should return ubyte instead of void, only I haven't been
> able to find how to do it. Any suggestion would be welcome.
>
> Thanks in advance.

So I had a go at this and found I struggled looking at "magic" functions and methods.
Turns out there is a much simpler answer.

int getAge(int yyyy, int mm, int dd) {
  import std.datetime;
  auto t1 = cast(DateTime)SysTime(Date(yyyy, mm, dd));
  auto t2 = cast(DateTime)Clock.currTime();

  int numYears;
  while(t2 > t1) {
     t1.add!"years"(1);
     numYears++;
  }

  return numYears;
}

On Sunday, 15 January 2017 at 07:25:26 UTC, rikki cattermole wrote:
> So I had a go at this and found I struggled looking at "magic" functions and methods.
> Turns out there is a much simpler answer.
>
> int getAge(int yyyy, int mm, int dd) {
>   import std.datetime;
>   auto t1 = cast(DateTime)SysTime(Date(yyyy, mm, dd));
>   auto t2 = cast(DateTime)Clock.currTime();
>
>   int numYears;
>   while(t2 > t1) {
>      t1.add!"years"(1);
>      numYears++;
>   }
>
>   return numYears;
> }


Well... correct me if I am wrong, but isn't t1.add!"years"(1) simply adding one year to t1?

I cleaned up the function a little, but it still feels like a hack:

uint getAge(uint yyyy, uint mm, uint dd) {
  import std.datetime;
  SysTime t = Clock.currTime;
  ubyte correction = 0;
  if(
    (t.month < mm) ||
    ( (t.month == mm) && (t.day < dd) )
  ) correction += 1;
  return (t.year - yyyy - correction);
}

Isn't there anything better?

On 15/01/2017 9:40 PM, Nestor wrote:
> I cleaned up the function a little, but it still feels like a hack:
>
> uint getAge(uint yyyy, uint mm, uint dd) {
>   import std.datetime;
>   SysTime t = Clock.currTime;
>   ubyte correction = 0;
>   if(
>     (t.month < mm) ||
>     ( (t.month == mm) && (t.day < dd) )
>   ) correction += 1;
>   return (t.year - yyyy - correction);
> }
>
> Isn't there anything better?

The problem with this is that it won't take into account leap years.

On Sunday, 15 January 2017 at 08:40:37 UTC, Nestor wrote:
> I cleaned up the function a little, but it still feels like a hack:
>
> uint getAge(uint yyyy, uint mm, uint dd) {
>   import std.datetime;
>   SysTime t = Clock.currTime;
>   ubyte correction = 0;
>   if(
>     (t.month < mm) ||
>     ( (t.month == mm) && (t.day < dd) )
>   ) correction += 1;
>   return (t.year - yyyy - correction);
> }
>
> Isn't there anything better?

It doesn't feel like a hack to me, because it's simple and correct code that comply with the common definition of a person's age. The only inaccuracy I can think of is about people born on February 29th...

On 01/15/2017 07:58 AM, Nestor wrote:
> I eventually came up with this, but it seems an ugly hack:
>
> import std.stdio;
>
> uint getAge(int yyyy, ubyte mm, ubyte dd) {
>   ubyte correction;
>   import std.datetime;
>   SysTime t = Clock.currTime();
>   if (t.month < mm) correction = 1;
>   else if (t.month == mm) correction = (t.day < dd) ? 1 : 0;
>   else correction = 0;
>   return (t.year - yyyy - correction);
> }
>
> void main() {
>   try
>     writefln("Edad: %s años.", getAge(1958, 1, 21));
>   catch(Exception e) {
>     writefln("%s.\n(%s, line %s)", e.msg, e.file, e.line);
>   }
> }

That's the better approach, I think. Years have variable lengths. Determining "age" in years works by comparing dates, not durations.

I would write it like this, but as far as I see yours does the same thing:

----
int getAge(int yyyy, int mm, int dd)
{
    import std.datetime;

    immutable SysTime now = Clock.currTime();
    immutable int years = now.year - yyyy;

    return mm > now.month || mm == now.month && dd > now.day
        ? years - 1 // birthday hasn't come yet this year
        : years; // birthday has already been this year
}

void main()
{
    import std.stdio;

    /* Day of writing: 2017-01-15 */
    writeln(getAge(1980, 1, 1)); /* 37 */
    writeln(getAge(1980, 1, 15)); /* 37 (birthday is today) */
    writeln(getAge(1980, 1, 30)); /* 36 */
    writeln(getAge(1980, 6, 1)); /* 36 */
}
----

> Isn't there a built-in function to do this?

If there is, finding it in std.datetime would take me longer than writing it myself.

On Sunday, 15 January 2017 at 11:01:28 UTC, biozic wrote:
> On Sunday, 15 January 2017 at 08:40:37 UTC, Nestor wrote:
>> I cleaned up the function a little, but it still feels like a hack:
>>
>> uint getAge(uint yyyy, uint mm, uint dd) {
>>   import std.datetime;
>>   SysTime t = Clock.currTime;
>>   ubyte correction = 0;
>>   if(
>>     (t.month < mm) ||
>>     ( (t.month == mm) && (t.day < dd) )
>>   ) correction += 1;
>>   return (t.year - yyyy - correction);
>> }
>>
>> Isn't there anything better?
>
> It doesn't feel like a hack to me, because it's simple and correct code that comply with the common definition of a person's age. The only inaccuracy I can think of is about people born on February 29th...

I know. I thought about it as well, but it's not something you can deal with cleanly.

For example, take a baby born in february 29 of year 2000 (leap year). In february 28 of 2001 that baby was one day short to one year.

Family can make a concession and celebrate birthdays in february 28 of non-leap years, but march 1 is the actual day when the year of life completes. Which one to choose?

Another way to deal with this is modifying the function to take a parameter which allows to do a relaxed calculation in non-leap years if one so desires.