589 lines
20 KiB
Factor
589 lines
20 KiB
Factor
! Copyright (C) 2008 Doug Coleman.
|
|
! See http://factorcode.org/license.txt for BSD license.
|
|
USING: arrays kernel math strings help.markup help.syntax
|
|
math.order ;
|
|
IN: calendar
|
|
|
|
HELP: duration
|
|
{ $description "A duration is a period of time years, months, days, hours, minutes, and seconds. All duration slots can store " { $link real } " numbers. Compare two durations with the " { $link <=> } " word." } ;
|
|
|
|
HELP: timestamp
|
|
{ $description "A timestamp is a date and a time with a timezone offset. Timestamp slots must store integers except for " { $snippet "seconds" } ", which stores reals, and " { $snippet "gmt-offset" } ", which stores a " { $link duration } ". Compare two durations with the " { $link <=> } " word." } ;
|
|
|
|
{ timestamp duration } related-words
|
|
|
|
HELP: gmt-offset-duration
|
|
{ $values { "duration" duration } }
|
|
{ $description "Returns a " { $link duration } " object with the GMT offset returned by " { $link gmt-offset } "." } ;
|
|
|
|
HELP: <date>
|
|
{ $values { "year" integer } { "month" integer } { "day" integer } { "timestamp" timestamp } }
|
|
{ $description "Returns a timestamp object representing the start of the specified day in your current timezone." }
|
|
{ $examples
|
|
{ $example "USING: accessors calendar prettyprint ;"
|
|
"2010 12 25 <date> instant >>gmt-offset ."
|
|
"T{ timestamp { year 2010 } { month 12 } { day 25 } }"
|
|
}
|
|
} ;
|
|
|
|
HELP: average-month
|
|
{ $values { "value" ratio } }
|
|
{ $description "The length of an average month averaged over 400 years. Used internally for adding an arbitrary real number of months to a timestamp." } ;
|
|
|
|
HELP: months-per-year
|
|
{ $values { "value" integer } }
|
|
{ $description "Returns the number of months in a year." } ;
|
|
|
|
HELP: days-per-year
|
|
{ $values { "value" ratio } }
|
|
{ $description "Returns the number of days in a year averaged over 400 years. Used internally for adding an arbitrary real number of days to a timestamp." } ;
|
|
|
|
HELP: hours-per-year
|
|
{ $values { "value" ratio } }
|
|
{ $description "Returns the number of hours in a year averaged over 400 years. Used internally for adding an arbitrary real number of hours to a timestamp." } ;
|
|
|
|
HELP: minutes-per-year
|
|
{ $values { "value" ratio } }
|
|
{ $description "Returns the number of minutes in a year averaged over 400 years. Used internally for adding an arbitrary real number of minutes to a timestamp." } ;
|
|
|
|
HELP: seconds-per-year
|
|
{ $values { "value" integer } }
|
|
{ $description "Returns the number of seconds in a year averaged over 400 years. Used internally for adding an arbitrary real number of seconds to a timestamp." } ;
|
|
|
|
HELP: julian-day-number
|
|
{ $values { "year" integer } { "month" integer } { "day" integer } { "n" integer } }
|
|
{ $description "Calculates the Julian day number from a year, month, and day. The difference between two Julian day numbers is the number of days that have elapsed between the two corresponding dates." }
|
|
{ $warning "Not valid before year -4800 BCE." } ;
|
|
|
|
HELP: julian-day-number>date
|
|
{ $values { "n" integer } { "year" integer } { "month" integer } { "day" integer } }
|
|
{ $description "Converts from a Julian day number back to a year, month, and day." } ;
|
|
{ julian-day-number julian-day-number>date } related-words
|
|
|
|
HELP: >date<
|
|
{ $values { "timestamp" timestamp } { "year" integer } { "month" integer } { "day" integer } }
|
|
{ $description "Explodes a " { $snippet "timestamp" } " into its year, month, and day components." }
|
|
{ $examples { $example "USING: arrays calendar prettyprint ;"
|
|
"2010 8 24 <date> >date< 3array ."
|
|
"{ 2010 8 24 }"
|
|
}
|
|
} ;
|
|
|
|
HELP: >time<
|
|
{ $values { "timestamp" timestamp } { "hour" integer } { "minute" integer } { "second" integer } }
|
|
{ $description "Explodes a " { $snippet "timestamp" } " into its hour, minute, and second components." }
|
|
{ $examples { $example "USING: arrays calendar prettyprint ;"
|
|
"now noon >time< 3array ."
|
|
"{ 12 0 0 }"
|
|
}
|
|
} ;
|
|
|
|
{ >date< >time< } related-words
|
|
|
|
HELP: instant
|
|
{ $values { "duration" duration } }
|
|
{ $description "Pushes a " { $snippet "duration" } " of zero seconds." } ;
|
|
|
|
HELP: years
|
|
{ $values { "x" number } { "duration" duration } }
|
|
{ $description "Creates a duration object with the specified number of years." } ;
|
|
|
|
HELP: months
|
|
{ $values { "x" number } { "duration" duration } }
|
|
{ $description "Creates a duration object with the specified number of months." } ;
|
|
|
|
HELP: days
|
|
{ $values { "x" number } { "duration" duration } }
|
|
{ $description "Creates a duration object with the specified number of days." } ;
|
|
|
|
HELP: weeks
|
|
{ $values { "x" number } { "duration" duration } }
|
|
{ $description "Creates a duration object with the specified number of weeks." } ;
|
|
|
|
HELP: hours
|
|
{ $values { "x" number } { "duration" duration } }
|
|
{ $description "Creates a duration object with the specified number of hours." } ;
|
|
|
|
HELP: minutes
|
|
{ $values { "x" number } { "duration" duration } }
|
|
{ $description "Creates a duration object with the specified number of minutes." } ;
|
|
|
|
HELP: seconds
|
|
{ $values { "x" number } { "duration" duration } }
|
|
{ $description "Creates a duration object with the specified number of seconds." } ;
|
|
|
|
HELP: milliseconds
|
|
{ $values { "x" number } { "duration" duration } }
|
|
{ $description "Creates a duration object with the specified number of milliseconds." } ;
|
|
|
|
HELP: microseconds
|
|
{ $values { "x" number } { "duration" duration } }
|
|
{ $description "Creates a duration object with the specified number of microseconds." } ;
|
|
|
|
HELP: nanoseconds
|
|
{ $values { "x" number } { "duration" duration } }
|
|
{ $description "Creates a duration object with the specified number of nanoseconds." } ;
|
|
|
|
{ years months days hours minutes seconds milliseconds microseconds nanoseconds } related-words
|
|
|
|
HELP: leap-year?
|
|
{ $values { "obj" object } { "?" boolean } }
|
|
{ $description "Returns " { $link t } " if the object represents a leap year." }
|
|
{ $examples
|
|
{ $example "USING: calendar prettyprint ;"
|
|
"2008 leap-year? ."
|
|
"t"
|
|
}
|
|
{ $example "USING: calendar prettyprint ;"
|
|
"2010 1 1 <date> leap-year? ."
|
|
"f"
|
|
}
|
|
} ;
|
|
|
|
HELP: time+
|
|
{ $values { "time1" "timestamp or duration" } { "time2" "timestamp or duration" } { "time3" "timestamp or duration" } }
|
|
{ $description "Adds two durations to produce a duration or adds a timestamp and a duration to produce a timestamp. The calculation takes timezones into account." }
|
|
{ $examples
|
|
{ $example "USING: calendar math.order prettyprint ;"
|
|
"10 months 2 months time+ 1 years <=> ."
|
|
"+eq+"
|
|
}
|
|
{ $example "USING: accessors calendar math.order prettyprint ;"
|
|
"2010 1 1 <date> 3 days time+ day>> ."
|
|
"4"
|
|
}
|
|
} ;
|
|
|
|
HELP: duration>years
|
|
{ $values { "duration" duration } { "x" number } }
|
|
{ $description "Calculates the length of a duration in years." }
|
|
{ $examples
|
|
{ $example "USING: calendar prettyprint ;"
|
|
"6 months duration>years ."
|
|
"1/2"
|
|
}
|
|
} ;
|
|
|
|
HELP: duration>months
|
|
{ $values { "duration" duration } { "x" number } }
|
|
{ $description "Calculates the length of a duration in months." }
|
|
{ $examples
|
|
{ $example "USING: calendar prettyprint ;"
|
|
"30 days duration>months ."
|
|
"16000/16233"
|
|
}
|
|
} ;
|
|
|
|
HELP: duration>days
|
|
{ $values { "duration" duration } { "x" number } }
|
|
{ $description "Calculates the length of a duration in days." }
|
|
{ $examples
|
|
{ $example "USING: calendar prettyprint ;"
|
|
"6 hours duration>days ."
|
|
"1/4"
|
|
}
|
|
} ;
|
|
|
|
HELP: duration>hours
|
|
{ $values { "duration" duration } { "x" number } }
|
|
{ $description "Calculates the length of a duration in hours." }
|
|
{ $examples
|
|
{ $example "USING: calendar prettyprint ;"
|
|
"3/4 days duration>hours ."
|
|
"18"
|
|
}
|
|
} ;
|
|
HELP: duration>minutes
|
|
{ $values { "duration" duration } { "x" number } }
|
|
{ $description "Calculates the length of a duration in minutes." }
|
|
{ $examples
|
|
{ $example "USING: calendar prettyprint ;"
|
|
"6 hours duration>minutes ."
|
|
"360"
|
|
}
|
|
} ;
|
|
HELP: duration>seconds
|
|
{ $values { "duration" duration } { "x" number } }
|
|
{ $description "Calculates the length of a duration in seconds." }
|
|
{ $examples
|
|
{ $example "USING: calendar prettyprint ;"
|
|
"6 minutes duration>seconds ."
|
|
"360"
|
|
}
|
|
} ;
|
|
|
|
HELP: duration>milliseconds
|
|
{ $values { "duration" duration } { "x" number } }
|
|
{ $description "Calculates the length of a duration in milliseconds." }
|
|
{ $examples
|
|
{ $example "USING: calendar prettyprint ;"
|
|
"6 seconds duration>milliseconds ."
|
|
"6000"
|
|
}
|
|
} ;
|
|
|
|
HELP: duration>microseconds
|
|
{ $values { "duration" duration } { "x" number } }
|
|
{ $description "Calculates the length of a duration in microseconds." }
|
|
{ $examples
|
|
{ $example "USING: calendar prettyprint ;"
|
|
"6 seconds duration>microseconds ."
|
|
"6000000"
|
|
}
|
|
} ;
|
|
|
|
HELP: duration>nanoseconds
|
|
{ $values { "duration" duration } { "x" number } }
|
|
{ $description "Calculates the length of a duration in nanoseconds." }
|
|
{ $examples
|
|
{ $example "USING: calendar prettyprint ;"
|
|
"6 seconds duration>nanoseconds ."
|
|
"6000000000"
|
|
}
|
|
} ;
|
|
|
|
{ duration>years duration>months duration>days duration>hours duration>minutes duration>seconds duration>milliseconds duration>microseconds duration>nanoseconds } related-words
|
|
|
|
|
|
HELP: time-
|
|
{ $values { "time1" "timestamp or duration" } { "time2" "timestamp or duration" } { "time3" "timestamp or duration" } }
|
|
{ $description "Subtracts two durations to produce a duration or subtracts a duration from a timestamp to produce a timestamp. The calculation takes timezones into account." }
|
|
{ $examples
|
|
{ $example "USING: calendar math.order prettyprint ;"
|
|
"10 months 2 months time- 8 months <=> ."
|
|
"+eq+"
|
|
}
|
|
{ $example "USING: accessors calendar math.order prettyprint ;"
|
|
"2010 1 1 <date> 3 days time- day>> ."
|
|
"29"
|
|
}
|
|
} ;
|
|
|
|
HELP: convert-timezone
|
|
{ $values { "timestamp" timestamp } { "duration" duration } { "timestamp'" timestamp } }
|
|
{ $description "Converts the " { $snippet "timestamp" } "'s " { $snippet "gmt-offset" } " to the GMT offset represented by the " { $snippet "duration" } "." }
|
|
{ $examples
|
|
{ $example "USING: accessors calendar prettyprint ;"
|
|
"gmt noon instant -5 >>hour convert-timezone gmt-offset>> hour>> ."
|
|
"-5"
|
|
}
|
|
} ;
|
|
|
|
HELP: >local-time
|
|
{ $values { "timestamp" timestamp } { "timestamp'" timestamp } }
|
|
{ $description "Converts the " { $snippet "timestamp" } " to the timezone of your computer." }
|
|
{ $examples
|
|
{ $example "USING: accessors calendar kernel prettyprint ;"
|
|
"now gmt >local-time [ gmt-offset>> ] same? ."
|
|
"t"
|
|
}
|
|
} ;
|
|
|
|
HELP: >gmt
|
|
{ $values { "timestamp" timestamp } { "timestamp'" timestamp } }
|
|
{ $description "Converts the " { $snippet "timestamp" } " to the GMT timezone." }
|
|
{ $examples
|
|
{ $example "USING: accessors calendar kernel prettyprint ;"
|
|
"now >gmt gmt-offset>> hour>> ."
|
|
"0"
|
|
}
|
|
} ;
|
|
|
|
HELP: time*
|
|
{ $values { "obj1" object } { "obj2" object } { "obj3" object } }
|
|
{ $description "Multiplies each time slot of a timestamp or duration by a number and make a new duration from the result. Used in the implementation of " { $link before } "." } ;
|
|
{ time+ time- time* } related-words
|
|
|
|
HELP: before
|
|
{ $values { "duration" duration } { "-duration" duration } }
|
|
{ $description "Negates a duration." }
|
|
{ $examples
|
|
{ $example "USING: accessors calendar prettyprint ;"
|
|
"3 hours before now noon time+ hour>> ."
|
|
"9"
|
|
}
|
|
} ;
|
|
|
|
HELP: unix-1970
|
|
{ $values { "timestamp" timestamp } }
|
|
{ $description "Returns the beginning of UNIX time, or midnight, January 1, 1970." } ;
|
|
|
|
HELP: micros>timestamp
|
|
{ $values { "x" number } { "timestamp" timestamp } }
|
|
{ $description "Converts a number of microseconds into a timestamp value in GMT time." }
|
|
{ $examples
|
|
{ $example "USING: accessors calendar prettyprint ;"
|
|
"1000 micros>timestamp year>> ."
|
|
"1970"
|
|
}
|
|
} ;
|
|
|
|
HELP: gmt
|
|
{ $values { "timestamp" timestamp } }
|
|
{ $description "Returns the time right now, but in the GMT timezone." } ;
|
|
|
|
{ gmt now } related-words
|
|
|
|
HELP: now
|
|
{ $values { "timestamp" timestamp } }
|
|
{ $description "Returns the time right now in your computer's timezone." }
|
|
{ $examples
|
|
{ $unchecked-example "USING: calendar prettyprint ;"
|
|
"now ."
|
|
"T{ timestamp f 2008 9 1 16 38 24+801/1000 T{ duration f 0 0 0 -5 0 0 } }"
|
|
}
|
|
} ;
|
|
|
|
HELP: hence
|
|
{ $values { "duration" duration } { "timestamp" timestamp } }
|
|
{ $description "Computes a time in the future that is the " { $snippet "duration" } " added to the result of " { $link now } "." }
|
|
{ $examples
|
|
{ $unchecked-example
|
|
"USING: calendar prettyprint ;"
|
|
"10 hours hence ."
|
|
"T{ timestamp f 2008 9 2 2 47 45+943/1000 T{ duration f 0 0 0 -5 0 0 } }"
|
|
}
|
|
} ;
|
|
|
|
HELP: ago
|
|
{ $values { "duration" duration } { "timestamp" timestamp } }
|
|
{ $description "Computes a time in the past that is the " { $snippet "duration" } " subtracted from the result of " { $link now } "." }
|
|
{ $examples
|
|
{ $unchecked-example
|
|
"USING: calendar prettyprint ;"
|
|
"3 weeks ago ."
|
|
"T{ timestamp f 2008 8 11 16 49 52+99/500 T{ duration f 0 0 0 -5 0 0 } }"
|
|
}
|
|
} ;
|
|
|
|
HELP: zeller-congruence
|
|
{ $values { "year" integer } { "month" integer } { "day" integer } { "n" integer } }
|
|
{ $description "An implementation of an algorithm that computes the day of the week given a date. Days are indexed starting from Sunday, which is index 0." }
|
|
{ $notes "User code should use the " { $link day-of-week } " word, which takes a " { $snippet "timestamp" } " instead of integers." } ;
|
|
|
|
HELP: days-in-year
|
|
{ $values { "obj" "a timestamp or an integer" } { "n" integer } }
|
|
{ $description "Calculates the number of days in a given year." }
|
|
{ $examples
|
|
{ $example "USING: calendar prettyprint ;"
|
|
"2004 days-in-year ."
|
|
"366"
|
|
}
|
|
} ;
|
|
|
|
HELP: days-in-month
|
|
{ $values { "timestamp" timestamp } { "n" integer } }
|
|
{ $description "Calculates the number of days in a given month." }
|
|
{ $examples
|
|
{ $example "USING: calendar prettyprint ;"
|
|
"2008 8 24 <date> days-in-month ."
|
|
"31"
|
|
}
|
|
} ;
|
|
|
|
HELP: day-of-week
|
|
{ $values { "timestamp" timestamp } { "n" integer } }
|
|
{ $description "Calculates the index of the day of the week. Sunday will result in an index of 0." }
|
|
{ $examples
|
|
{ $example "USING: calendar prettyprint ;"
|
|
"now sunday day-of-week ."
|
|
"0"
|
|
}
|
|
} ;
|
|
|
|
HELP: day-of-year
|
|
{ $values { "timestamp" timestamp } { "n" integer } }
|
|
{ $description "Calculates the day of the year, resulting in a number from 1 to 366 (leap years)." }
|
|
{ $examples
|
|
{ $example "USING: calendar prettyprint ;"
|
|
"2008 1 4 <date> day-of-year ."
|
|
"4"
|
|
}
|
|
} ;
|
|
|
|
HELP: sunday
|
|
{ $values { "timestamp" timestamp } { "new-timestamp" timestamp } }
|
|
{ $description "Returns the Sunday from the current week, which starts on a Sunday." } ;
|
|
|
|
HELP: monday
|
|
{ $values { "timestamp" timestamp } { "new-timestamp" timestamp } }
|
|
{ $description "Returns the Monday from the current week, which starts on a Sunday." } ;
|
|
|
|
HELP: tuesday
|
|
{ $values { "timestamp" timestamp } { "new-timestamp" timestamp } }
|
|
{ $description "Returns the Tuesday from the current week, which starts on a Sunday." } ;
|
|
|
|
HELP: wednesday
|
|
{ $values { "timestamp" timestamp } { "new-timestamp" timestamp } }
|
|
{ $description "Returns the Wednesday from the current week, which starts on a Sunday." } ;
|
|
|
|
HELP: thursday
|
|
{ $values { "timestamp" timestamp } { "new-timestamp" timestamp } }
|
|
{ $description "Returns the Thursday from the current week, which starts on a Sunday." } ;
|
|
|
|
HELP: friday
|
|
{ $values { "timestamp" timestamp } { "new-timestamp" timestamp } }
|
|
{ $description "Returns the Friday from the current week, which starts on a Sunday." } ;
|
|
|
|
HELP: saturday
|
|
{ $values { "timestamp" timestamp } { "new-timestamp" timestamp } }
|
|
{ $description "Returns the Saturday from the current week, which starts on a Sunday." } ;
|
|
|
|
{ sunday monday tuesday wednesday thursday friday saturday } related-words
|
|
|
|
HELP: midnight
|
|
{ $values { "timestamp" timestamp } { "new-timestamp" timestamp } }
|
|
{ $description "Returns a new timestamp that represents the day at midnight, or the beginning of the day." } ;
|
|
|
|
HELP: noon
|
|
{ $values { "timestamp" timestamp } { "new-timestamp" timestamp } }
|
|
{ $description "Returns a new timestamp that represents the day at noon, or the middle of the day." } ;
|
|
|
|
HELP: today
|
|
{ $values { "timestamp" timestamp } }
|
|
{ $description "Returns a timestamp that represents today at midnight." } ;
|
|
|
|
HELP: beginning-of-month
|
|
{ $values { "timestamp" timestamp } { "new-timestamp" timestamp } }
|
|
{ $description "Returns a new timestamp with the day set to one." } ;
|
|
|
|
HELP: beginning-of-week
|
|
{ $values { "timestamp" timestamp } { "new-timestamp" timestamp } }
|
|
{ $description "Returns a new timestamp where the day of the week is Sunday." } ;
|
|
|
|
HELP: beginning-of-year
|
|
{ $values { "object" object } { "new-timestamp" timestamp } }
|
|
{ $description "Returns a new timestamp with the month and day set to one, or January 1 of the input timestamp, given a year or a timestamp." } ;
|
|
|
|
HELP: time-since-midnight
|
|
{ $values { "timestamp" timestamp } { "duration" duration } }
|
|
{ $description "Calculates a " { $snippet "duration" } " that represents the elapsed time since midnight of the input " { $snippet "timestamp" } "." } ;
|
|
|
|
HELP: since-1970
|
|
{ $values
|
|
{ "duration" duration }
|
|
{ "timestamp" timestamp } }
|
|
{ $description "Adds the duration to the beginning of Unix time and returns the result as a timestamp." } ;
|
|
|
|
ARTICLE: "calendar" "Calendar"
|
|
"The " { $vocab-link "calendar" } " vocabulary defines two data types and a set of operations on them:"
|
|
{ $subsections
|
|
timestamp
|
|
duration
|
|
}
|
|
"Durations represent spans of time:"
|
|
{ $subsections "using-durations" }
|
|
"Arithmetic on timestamps and durations:"
|
|
{ $subsections "timestamp-arithmetic" }
|
|
"Getting the current timestamp:"
|
|
{ $subsections
|
|
now
|
|
gmt
|
|
}
|
|
"Time zones:"
|
|
{ $subsections
|
|
>local-time
|
|
>gmt
|
|
convert-timezone
|
|
}
|
|
"Timestamps relative to each other:"
|
|
{ $subsections "relative-timestamps" }
|
|
"Operations on units of time:"
|
|
{ $subsections
|
|
"years"
|
|
"months"
|
|
"days"
|
|
}
|
|
"Both " { $link timestamp } "s and " { $link duration } "s implement the " { $link "math.order" } "."
|
|
$nl
|
|
"Meta-data about the calendar:"
|
|
{ $subsections "calendar-facts" } ;
|
|
|
|
ARTICLE: "timestamp-arithmetic" "Timestamp arithmetic"
|
|
"Adding timestamps and durations, or durations and durations:"
|
|
{ $subsections time+ }
|
|
"Subtracting:"
|
|
{ $subsections time- }
|
|
"Element-wise multiplication:"
|
|
{ $subsections time* } ;
|
|
|
|
ARTICLE: "using-durations" "Using durations"
|
|
"Creating a duration object:"
|
|
{ $subsections
|
|
years
|
|
months
|
|
weeks
|
|
days
|
|
hours
|
|
minutes
|
|
seconds
|
|
milliseconds
|
|
microseconds
|
|
nanoseconds
|
|
instant
|
|
}
|
|
"Converting a duration to a number:"
|
|
{ $subsections
|
|
duration>years
|
|
duration>months
|
|
duration>days
|
|
duration>hours
|
|
duration>minutes
|
|
duration>seconds
|
|
duration>milliseconds
|
|
duration>microseconds
|
|
duration>nanoseconds
|
|
} ;
|
|
|
|
ARTICLE: "relative-timestamps" "Relative timestamps"
|
|
"In the future:"
|
|
{ $subsections hence }
|
|
"In the past:"
|
|
{ $subsections ago }
|
|
"Invert a duration:"
|
|
{ $subsections before }
|
|
"Days of the week relative to " { $link now } ":"
|
|
{ $subsections
|
|
sunday
|
|
monday
|
|
tuesday
|
|
wednesday
|
|
thursday
|
|
friday
|
|
saturday
|
|
}
|
|
"New timestamps relative to calendar events:"
|
|
{ $subsections
|
|
beginning-of-year
|
|
beginning-of-month
|
|
beginning-of-week
|
|
midnight
|
|
noon
|
|
} ;
|
|
|
|
ARTICLE: "calendar-facts" "Calendar facts"
|
|
"Calendar facts:"
|
|
{ $subsections
|
|
average-month
|
|
months-per-year
|
|
days-per-year
|
|
hours-per-year
|
|
minutes-per-year
|
|
seconds-per-year
|
|
days-in-month
|
|
day-of-year
|
|
day-of-week
|
|
}
|
|
"Calculating a Julian day number:"
|
|
{ $subsections julian-day-number }
|
|
"Calculate a timestamp:"
|
|
{ $subsections julian-day-number>date } ;
|
|
|
|
ARTICLE: "years" "Year operations"
|
|
"Leap year predicate:"
|
|
{ $subsections leap-year? }
|
|
"Find the number of days in a year:"
|
|
{ $subsections days-in-year } ;
|
|
|
|
ABOUT: "calendar"
|