[X] Make months and years not convertible to seconds:

* The Gregorian average of months and years is an
  integral number of seconds.
* This patch slightly tweaks the average to make it
  not an integral number of seconds, and thus these
  units no longer implicitly convert to seconds.
* This will flag naive  mixing of years, months and seconds
  as a compile time error.
This commit is contained in:
Howard Hinnant
2015-08-04 18:48:48 -04:00
parent 756460892c
commit fd485c5383
2 changed files with 48 additions and 3 deletions

3
date.h
View File

@@ -45,7 +45,8 @@ using weeks = std::chrono::duration
<int, std::ratio_multiply<std::ratio<7>, days::period>>; <int, std::ratio_multiply<std::ratio<7>, days::period>>;
using years = std::chrono::duration using years = std::chrono::duration
<int, std::ratio_multiply<std::ratio<146097, 400>, days::period>>; <int, std::ratio_subtract<std::ratio_multiply<std::ratio<146097, 400>, days::period>,
std::ratio<1, 7>>>;
using months = std::chrono::duration using months = std::chrono::duration
<int, std::ratio_divide<years::period, std::ratio<12>>>; <int, std::ratio_divide<years::period, std::ratio<12>>>;

View File

@@ -25,9 +25,53 @@
#include <type_traits> #include <type_traits>
static_assert(date::days{1} == std::chrono::seconds{86400}, ""); static_assert(date::days{1} == std::chrono::seconds{86400}, "");
static_assert(date::days{1} == std::chrono::hours{24}, "");
static_assert( std::is_convertible<date::days, std::chrono::seconds>{}, "");
static_assert( std::is_convertible<date::days, std::chrono::minutes>{}, "");
static_assert( std::is_convertible<date::days, std::chrono::hours>{}, "");
static_assert(!std::is_convertible<date::days, date::weeks>{}, "");
static_assert(!std::is_convertible<date::days, date::months>{}, "");
static_assert(!std::is_convertible<date::days, date::years>{}, "");
static_assert(date::weeks{1} == std::chrono::seconds{604800}, ""); static_assert(date::weeks{1} == std::chrono::seconds{604800}, "");
static_assert(date::months{1} == std::chrono::seconds{2629746}, ""); static_assert(date::weeks{1} == date::days{7}, "");
static_assert(date::years{1} == std::chrono::seconds{31556952}, ""); static_assert( std::is_convertible<date::weeks, std::chrono::seconds>{}, "");
static_assert( std::is_convertible<date::weeks, std::chrono::minutes>{}, "");
static_assert( std::is_convertible<date::weeks, std::chrono::hours>{}, "");
static_assert( std::is_convertible<date::weeks, date::days>{}, "");
static_assert(!std::is_convertible<date::weeks, date::months>{}, "");
static_assert(!std::is_convertible<date::weeks, date::years>{}, "");
static_assert(
std::chrono::seconds{2629745} < date::months{1} &&
date::months{1} < std::chrono::seconds{2629746}, "");
static_assert(date::days{30} < date::months{1} && date::months{1} < date::days{31}, "");
static_assert(date::weeks{4} < date::months{1} && date::months{1} < date::weeks{5}, "");
static_assert(!std::is_convertible<date::months, date::years>{}, "");
static_assert(!std::is_convertible<date::months, date::weeks>{}, "");
static_assert(!std::is_convertible<date::months, date::days>{}, "");
static_assert(!std::is_convertible<date::months, std::chrono::hours>{}, "");
static_assert(!std::is_convertible<date::months, std::chrono::minutes>{}, "");
static_assert(!std::is_convertible<date::months, std::chrono::seconds>{}, "");
static_assert(!std::is_convertible<date::months, std::chrono::milliseconds>{}, "");
static_assert(!std::is_convertible<date::months, std::chrono::microseconds>{}, "");
static_assert(!std::is_convertible<date::months, std::chrono::nanoseconds>{}, "");
static_assert(
std::chrono::seconds{31556951} < date::years{1} &&
date::years{1} < std::chrono::seconds{31556952}, "");
static_assert(date::days{365} < date::years{1} && date::years{1} < date::days{366}, "");
static_assert(date::weeks{52} < date::years{1} && date::years{1} < date::weeks{53}, "");
static_assert(date::years{1} == date::months{12}, "");
static_assert( std::is_convertible<date::years, date::months>{}, "");
static_assert(!std::is_convertible<date::years, date::weeks>{}, "");
static_assert(!std::is_convertible<date::years, date::days>{}, "");
static_assert(!std::is_convertible<date::years, std::chrono::hours>{}, "");
static_assert(!std::is_convertible<date::years, std::chrono::minutes>{}, "");
static_assert(!std::is_convertible<date::years, std::chrono::seconds>{}, "");
static_assert(!std::is_convertible<date::years, std::chrono::milliseconds>{}, "");
static_assert(!std::is_convertible<date::years, std::chrono::microseconds>{}, "");
static_assert(!std::is_convertible<date::years, std::chrono::nanoseconds>{}, "");
static_assert(std::is_same<date::day_point::duration, date::days>{}, ""); static_assert(std::is_same<date::day_point::duration, date::days>{}, "");