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Updated FAQ (markdown)

Howard Hinnant
2019-12-12 14:19:45 -08:00
parent fa44fbded9
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10
FAQ.md

@@ -27,29 +27,29 @@ The programmer would probably use it like this:
year_month_day
get_meeting_date(year y, month m)
{
return year_month_day{tue[3]/m/y + days{1}};
return year_month_day{Tuesday[3]/m/y + days{1}};
}
That is super-compact syntax! Here is what it costs:
1. Convert `tue[3]/m/y` (`year_month_weekday`) to `sys_days` in order to add `days`.
1. Convert `Tuesday[3]/m/y` (`year_month_weekday`) to `sys_days` in order to add `days`.
2. Convert the `sys_days` computed back to `year_month_weekday`.
3. Convert the temporary `year_month_weekday` computed in 2 back to `sys_days`.
4. Convert the `sys_days` to a `year_month_day`.
4 conversions.
Here is the way you have to write this function today (because `tue[3]/m/y + days{1}` is a compile-time error):
Here is the way you have to write this function today (because `Tuesday[3]/m/y + days{1}` is a compile-time error):
year_month_day
get_meeting_date(year y, month m)
{
return year_month_day{sys_days{tue[3]/m/y} + days{1}};
return year_month_day{sys_days{Tuesday[3]/m/y} + days{1}};
}
The syntax is slightly more verbose in that you have to explicitly convert the `year_month_weekday` into a `sys_days` in order to perform the day-oriented arithmetic. Here is what it costs:
1. Convert `tue[3]/m/y` (`year_month_weekday`) to `sys_days` in order to add `days`.
1. Convert `Tuesday[3]/m/y` (`year_month_weekday`) to `sys_days` in order to add `days`.
2. Convert the `sys_days` to a `year_month_day`.
2 conversions. Roughly twice as fast!