Replace | by ` in (most) comments.

astronomy/date_time.hpp

@@ -23,12 +23,12 @@ namespace internal {
 class Date final {
  public:
   // The calendar is Gregorian by default starting in 1583; before that,
-  // |calendar| is required.
+  // `calendar` is required.
   static constexpr Date YYYYMMDD(
       std::int64_t digits,
       std::optional<Calendar> calendar = std::nullopt);
   // The calendar is Gregorian by default starting in 1583; before that,
-  // |calendar| is required.
+  // `calendar` is required.
   static constexpr Date YYYYDDD(
       std::int64_t digits,
       std::optional<Calendar> calendar = std::nullopt);
@@ -37,21 +37,21 @@ class Date final {
   static constexpr Date YYYYwwD(std::int64_t digits);
 
   // The calendar is Gregorian by default starting in 1583; before that,
-  // |calendar| is required.
+  // `calendar` is required.
   static constexpr Date Calendar(
       int year, int month, int day,
       std::optional<Calendar> calendar = std::nullopt);
   // The calendar is Gregorian by default starting in 1583; before that,
-  // |calendar| is required.
+  // `calendar` is required.
   static constexpr Date Ordinal(
       int year, int day,
       std::optional<_date_time::Calendar> calendar = std::nullopt);
   // Since the calendar week number is an ISO 8601 construct, the year must be
   // at least 1583, and the calendar is Gregorian.
   static constexpr Date Week(int year, int week, int day);
 
-  // The julian date |jd| must not be negative; its fractional part must be one
-  // half, corresponding to 00:00 on the resulting |Date|.
+  // The julian date `jd` must not be negative; its fractional part must be one
+  // half, corresponding to 00:00 on the resulting `Date`.
   static constexpr Date JD(double jd);
 
   constexpr int year() const;
@@ -61,7 +61,7 @@ class Date final {
 
   constexpr int ordinal() const;
 
-  // The fractional part of |jd()| is one half, corresponding to 00:00 on the
+  // The fractional part of `jd()` is one half, corresponding to 00:00 on the
   // day represented by this object.
   constexpr double jd() const;
   constexpr int mjd() const;
@@ -93,7 +93,7 @@ class TimeOfDay final {
   constexpr int millisecond() const;
 
   constexpr bool is_leap_second() const;
-  // Whether |*this| is 24:00:00.
+  // Whether `*this` is 24:00:00.
   constexpr bool is_end_of_day() const;
 
  private:
@@ -107,7 +107,7 @@ class TimeOfDay final {
 
 class DateTime final {
  public:
-  // Checks that |time| does not represent a leap second unless |date| is the
+  // Checks that `time` does not represent a leap second unless `date` is the
   // last day of the month.
   constexpr DateTime(Date date, TimeOfDay time);
 
@@ -116,8 +116,8 @@ class DateTime final {
   constexpr Date const& date() const;
   constexpr TimeOfDay const& time() const;
 
-  // If |time()| is 24:00:00, returns an equivalent DateTime where midnight is
-  // expressed as 00:00:00 on the next day; otherwise, returns |*this|.
+  // If `time()` is 24:00:00, returns an equivalent DateTime where midnight is
+  // expressed as 00:00:00 on the next day; otherwise, returns `*this`.
   constexpr DateTime normalized_end_of_day() const;
 
  private:
@@ -146,7 +146,7 @@ class JulianDate final {
                        std::int64_t fraction_numerator,
                        std::int64_t fraction_denominator);
 
-  // These numbers are relative to J2000.  |fraction_denominator| is a positive
+  // These numbers are relative to J2000.  `fraction_denominator` is a positive
   // power of 10.
   std::int64_t const day_;
   std::int64_t const fraction_numerator_;

astronomy/date_time_body.hpp

@@ -56,17 +56,17 @@ constexpr int number_of_iso_weeks_in_year(int const year) {
              : 52;
 }
 
-// Returns the ordinal in |year| of the first day of the first week of |year|.
+// Returns the ordinal in `year` of the first day of the first week of `year`.
 // The result is in [-2, 4], with values in [-2, 0] meaning that the first week
-// of |year| starts in |year - 1|.
-// A result in [-2, 1] means that the first day of |year| is in the first week
-// of |year|; otherwise, it is in the last week of |year - 1|.
+// of `year` starts in `year - 1`.
+// A result in [-2, 1] means that the first day of `year` is in the first week
+// of `year`; otherwise, it is in the last week of `year - 1`.
 constexpr int ordinal_of_w_01_1(int const year) {
   return mod(2 - day_of_week_on_january_1st(year), 7, -2);
 }
 
-// Returns the number formed by taking |end - begin| increasingly significant
-// digits, starting from the digit of the (10 ** |begin|)s.
+// Returns the number formed by taking `end - begin` increasingly significant
+// digits, starting from the digit of the (10 ** `begin`)s.
 constexpr std::int64_t digit_range(std::int64_t const digits,
                                    int const begin,
                                    int const end) {
@@ -94,7 +94,7 @@ constexpr std::int64_t shift_right(std::int64_t const x, int const count) {
   return count == 0 ? x : shift_right(x / 10, count - 1);
 }
 
-// Implementation of class |Date|.
+// Implementation of class `Date`.
 
 constexpr Date Date::YYYYMMDD(
     std::int64_t const digits,
@@ -466,12 +466,12 @@ constexpr CStringIterator::CStringIterator(char const* const str,
 
 // Date parsing.
 
-// A |DateParser| contains information about a string necessary to interpret it
+// A `DateParser` contains information about a string necessary to interpret it
 // as a date representation.
 class DateParser final {
  public:
-  // Returns a |Date| corresponding to the representation |str|.
-  // Fails unless |str| is a date representation of one of the following forms:
+  // Returns a `Date` corresponding to the representation `str`.
+  // Fails unless `str` is a date representation of one of the following forms:
   // [YYYY-MM-DD], [YYYYMMDD], [YYYY-Www-D], [YYYYWwwD], [YYYY-DDD], [YYYYDDD],
   // with an optional prefix [J] or [G] and an optional sign.
   static constexpr Date Parse(char const* str, std::size_t size);
@@ -485,7 +485,7 @@ class DateParser final {
                        bool has_w,
                        int w_index);
 
-  // Returns a |DateParser| describing the given string. Fails if the string
+  // Returns a `DateParser` describing the given string. Fails if the string
   // does not exclusively consist of:
   //   - any number of decimal digits;
   //   - at most two hyphens;
@@ -501,7 +501,7 @@ class DateParser final {
                                         bool has_w,
                                         int w_index);
 
-  // Returns a |Date| corresponding to the string that |*this| describes.
+  // Returns a `Date` corresponding to the string that `*this` describes.
   // Fails if the format is invalid or the string represents an invalid date.
   constexpr Date ToDate(std::optional<Calendar> calendar, bool negative) const;
 
@@ -661,12 +661,12 @@ constexpr Date DateParser::ToDate(std::optional<Calendar> const calendar,
 
 // TimeOfDay parsing.
 
-// A |TimeParser| contains information about a string necessary to interpret it
+// A `TimeParser` contains information about a string necessary to interpret it
 // as a time representation.
 class TimeParser final {
  public:
-  // Returns a |TimeOfDay| corresponding to the representation |str|.
-  // Fails unless |str| is a valid time representation of one of the following
+  // Returns a `TimeOfDay` corresponding to the representation `str`.
+  // Fails unless `str` is a valid time representation of one of the following
   // forms: [hh:mm:ss], [hhmmss], [hh:mm:ss.ss̲], [hh:mm:ss,ss̲], [hhmmss.ss̲],
   // [hhmmss,ss̲], with at most three digits after the decimal mark.
   static constexpr TimeOfDay Parse(char const* str, std::size_t size);
@@ -680,7 +680,7 @@ class TimeParser final {
                        bool has_decimal_mark,
                        int decimal_mark_index);
 
-  // Returns a |TimeParser| describing the given string. Fails if the string
+  // Returns a `TimeParser` describing the given string. Fails if the string
   // does not exclusively consist of:
   // Fails if the string does not exclusively consist of:
   //   - any number of decimal digits;
@@ -697,7 +697,7 @@ class TimeParser final {
                                         bool has_decimal_mark,
                                         int decimal_mark_index);
 
-  // Returns a |TimeOfDay| corresponding to the string that |*this| describes.
+  // Returns a `TimeOfDay` corresponding to the string that `*this` describes.
   // Fails if the format is invalid or the string represents an invalid time.
   constexpr TimeOfDay ToTime() const;
 
@@ -837,15 +837,15 @@ constexpr TimeOfDay TimeParser::ToTime() const {
 
 // Julian date parsing.
 
-// A |JulianDateParser| contains information about a string necessary to
+// A `JulianDateParser` contains information about a string necessary to
 // interpret it as a Julian date.
 class JulianDateParser final {
  public:
-  // Returns a |JulianDate| corresponding to the representation |str|.
-  // Fails unless |str| is a valid time representation of the form [ddd] or
+  // Returns a `JulianDate` corresponding to the representation `str`.
+  // Fails unless `str` is a valid time representation of the form [ddd] or
   // [ddd.fff].
 
-  // Returns a |JulianDate| object corresponding to the given string interpreted
+  // Returns a `JulianDate` object corresponding to the given string interpreted
   // a Julian Date or a Modified Julian Date, respectively.
   static constexpr JulianDate ParseJD(char const* str, std::size_t size);
   static constexpr JulianDate ParseMJD(char const* str, std::size_t size);
@@ -855,7 +855,7 @@ class JulianDateParser final {
                              int digit_count,
                              int decimal_mark_index);
 
-  // Returns a |JulianDateParser| describing the given string. Fails if the
+  // Returns a `JulianDateParser` describing the given string. Fails if the
   // string is not of the form [ddd] or [ddd.fff] or if it has too many digits
   // to fit in a std::int64_t.
   static constexpr JulianDateParser ReadToEnd(char const* str,
@@ -866,7 +866,7 @@ class JulianDateParser final {
                                               bool has_decimal_mark,
                                               int decimal_mark_index);
 
-  // Returns a |JulianDate| corresponding to the string that |*this| describes.
+  // Returns a `JulianDate` corresponding to the string that `*this` describes.
   // Fails if the format is invalid.
   constexpr JulianDate ToJD() const;
   constexpr JulianDate ToMJD() const;

astronomy/epoch.hpp

@@ -2,7 +2,7 @@
 
 #include "geometry/instant.hpp"
 
-// |geometry::Instant| represents instants of Terrestrial Time (TT).  The
+// `geometry::Instant` represents instants of Terrestrial Time (TT).  The
 // utilities in this file provide its standard epoch and two ways of specifying
 // TT dates.
 
@@ -13,7 +13,7 @@ namespace internal {
 
 using namespace principia::geometry::_instant;
 
-// |J2000| represents to the standard epoch J2000.0.
+// `J2000` represents to the standard epoch J2000.0.
 // According to Resolution B1 (On the Use of Julian Dates) of the XXIIIrd IAU
 // general assembly, "it is recommended that JD be specified as SI seconds in
 // Terrestrial Time (TT)", see http://goo.gl/oPemRm. J2000.0 is by definition

astronomy/frames.hpp

@@ -57,7 +57,7 @@ using ICRS = Frame<serialization::Frame::SolarSystemTag,
 // - The time coordinate of the BCRS is TCB, and the time coordinate of the GCRS
 //   is TCG; TT is a linear scaling of TCG, and TDB is a linear scaling of TCB;
 //   for practical purposes TT and TDB are within 2 ms of each other;
-//   Principia's |Instant| is TT.
+//   Principia's `Instant` is TT.
 using GCRS = Frame<serialization::Frame::SolarSystemTag,
                    NonRotating,
                    Handedness::Right,
@@ -71,7 +71,7 @@ using GCRS = Frame<serialization::Frame::SolarSystemTag,
 // - This is identical to WGS84 at 1 m level, and to recent realizations of WGS
 //   84 at 10 cm level; the xz plane is a bit over a hundred metres from the
 //   Royal Observatory in Greenwich.
-//   Caveat: using |SphericalCoordinates<Length>| on ITRS coordinates is
+//   Caveat: using `SphericalCoordinates<Length>` on ITRS coordinates is
 //   inconsistent with WGS 84 latitudes; the WGS 84 geoid should be used.
 // - The ITRS is related to the European Terrestrial Reference System (ETRS89)
 //   by a time-dependent rigid transformation.

astronomy/lunar_eclipse_test.cpp

@@ -77,8 +77,8 @@ class LunarEclipseTest : public ::testing::Test {
     atmospheric_depth_ = (1.0 / 85.0 - 1.0 / 594.0) * r_earth_;
   }
 
-  // A positive |time_error| means that the actual contact happens after
-  // |current_time|.
+  // A positive `time_error` means that the actual contact happens after
+  // `current_time`.
   void CheckLunarUmbralEclipse(Instant const& current_time,
                                Sign const moon_offset_sign,
                                ApproximateQuantity<Angle> const& angular_error,
@@ -112,7 +112,7 @@ class LunarEclipseTest : public ::testing::Test {
               (r_earth_ + atmospheric_depth_ + moon_offset_sign * r_moon_) /
               Sin(umbral_half_aperture(t));
       // Angle between Earth and Moon as seen at
-      // |apex_of_moon_locus_at_umbral_contact|.
+      // `apex_of_moon_locus_at_umbral_contact`.
       return AngleBetween(apex_of_moon_locus_at_umbral_contact - q_earth,
                           apex_of_moon_locus_at_umbral_contact - q_moon);
     };
@@ -139,8 +139,8 @@ class LunarEclipseTest : public ::testing::Test {
               << " " << actual_contact_time - current_time;
   }
 
-  // A positive |time_error| means that the actual contact happens after
-  // |current_time|.
+  // A positive `time_error` means that the actual contact happens after
+  // `current_time`.
   void CheckLunarPenumbralEclipse(
       Instant const& current_time,
       Sign const moon_offset_sign,

astronomy/lunar_orbit_test.cpp

@@ -157,11 +157,11 @@ class LunarOrbitTest : public ::testing::TestWithParam<GeopotentialTruncation> {
   // This reference frame is non-rotating, with its origin at the selenocentre.
   // The axes are those of LunarSurface at J2000.
   // Note that this frame is not actually inertial, but we want to use it with
-  // |KeplerOrbit|.  Perhaps we should have a concept of non-rotating, and
-  // |KeplerOrbit| should check that; this is good enough for a test.
+  // `KeplerOrbit`.  Perhaps we should have a concept of non-rotating, and
+  // `KeplerOrbit` should check that; this is good enough for a test.
   using Selenocentric = Frame<struct SelenocentricTag, Inertial>;
 
-  // We do not use a |BodyCentredNonRotatingReferenceFrame| since that would use
+  // We do not use a `BodyCentredNonRotatingReferenceFrame` since that would use
   // ICRS axes.
   RigidMotion<ICRS, Selenocentric> ToSelenocentric(Instant const& t) {
     return RigidMotion<ICRS, Selenocentric>(

astronomy/orbit_analysis_test.cpp

@@ -153,7 +153,7 @@ class OrbitAnalysisTest : public ::testing::Test {
         earth_(*earth_1957_.rotating_body(*ephemeris_, "Earth")) {}
 
   // Returns a GCRS trajectory obtained by stitching together the trajectories
-  // of |sp3_orbit.satellites| in |sp3_orbit.files|.
+  // of `sp3_orbit.satellites` in `sp3_orbit.files`.
   not_null<std::unique_ptr<DiscreteTrajectory<GCRS>>> EarthCentredTrajectory(
       SP3Orbit const& sp3_orbit) {
     BodyCentredNonRotatingReferenceFrame<ICRS, GCRS> gcrs{ephemeris_.get(),

astronomy/orbit_ground_track.hpp

@@ -30,11 +30,11 @@ class OrbitGroundTrack {
   struct MeanSun {
     Instant epoch;
     // This mean longitude of the sun is with respect to the axes of
-    // |PrimaryCentred|.
+    // `PrimaryCentred`.
     Angle mean_longitude_at_epoch;
     // This year is the period of the above mean longitude; which kind of year
-    // it is depends on the definition of |PrimaryCentred|.  If |PrimaryCentred|
-    // has ICRS axes, it is the sidereal year; if |PrimaryCentred| is the
+    // it is depends on the definition of `PrimaryCentred`.  If `PrimaryCentred`
+    // has ICRS axes, it is the sidereal year; if `PrimaryCentred` is the
     // reference frame of the equator & equinox of the date, it is the tropical
     // year.
     Time year;
@@ -66,7 +66,7 @@ class OrbitGroundTrack {
   OrbitGroundTrack& operator=(OrbitGroundTrack&&) = default;
 
   // Returns an object that describes the properties of the ground track of
-  // |trajectory| as an orbit around |primary|; if |mean_sun| is provided,
+  // `trajectory` as an orbit around `primary`; if `mean_sun` is provided,
   // sun-synchronicity is analysed.
   template<typename PrimaryCentred, typename Inertial>
   static absl::StatusOr<OrbitGroundTrack> ForTrajectory(
@@ -76,7 +76,7 @@ class OrbitGroundTrack {
 
   // Given a nominal recurrence and the index of the first ascending pass east
   // of the equator (which must be odd and in [1, 2 Nᴛₒ - 1], where Nᴛₒ is
-  // |nominal_recurrence.number_of_revolutions()|), returns an object describing
+  // `nominal_recurrence.number_of_revolutions()`), returns an object describing
   // how the recurrence grid is aligned in longitude, and how well the actual
   // orbit follows that grid.
   EquatorCrossingLongitudes equator_crossing_longitudes(
@@ -97,9 +97,9 @@ class OrbitGroundTrack {
 
   std::vector<Angle> longitudes_of_equator_crossings_of_ascending_passes_;
   std::vector<Angle> longitudes_of_equator_crossings_of_descending_passes_;
-  // Whether |longitudes_of_equator_crossings_of_descending_passes_.front()| is
+  // Whether `longitudes_of_equator_crossings_of_descending_passes_.front()` is
   // the longitude of the pass preceding
-  // |longitudes_of_equator_crossings_of_ascending_passes_.front()|, rather than
+  // `longitudes_of_equator_crossings_of_ascending_passes_.front()`, rather than
   // the following one.
   bool first_descending_pass_before_first_ascending_pass_;
   std::optional<Interval<Angle>> mean_solar_times_of_ascending_nodes_;