srfi-19 | chickadee

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Documentation

This is a Chicken port of SRFI-19. This document only describes the extensions. For the SRFI-19 API see SRFI-19.

Core Procedures

The core procedures are those pertaining to time, date, and timezone:

(require-extension srfi-19-core)

The core procedures can be separately accessed:

(require-extension srfi-19-time)

(require-extension srfi-19-date)

(require-extension srfi-19-timezone)

(require-extension srfi-19-io)

SRFI-19 Document Changes

The nanosecond time object element is an integer between 0 and 999,999,999 inclusive. (The SRFI-19 document mis-states the value.)

A tz-offset value follows ISO 8601; positive for east of UTC, and negative for west. This is the opposite of the POSIX TZ environment variable.

Where the SRFI-19 document states a tz-offset argument a timezone-components object is also legal.

The string->date procedure allows the template-name argument to be optional. When missing the locale's date-time-format string is used. The supplied locale bundle's strings are invertible.

make-date

make-date NANOSECOND SECOND MINUTE HOUR DAY MONTH YEAR #!optional ZONE-OFFSET TZ-NAME DST-FLAGprocedure

Same as SRFI-19 except for the optional parameters and allowing a timezone-components object for the ZONE-OFFSET.

The ZONE-OFFSET is an integer or timezone-components. Default is the (timezone-locale-offset), the current locale timezone offset.

The TZ-NAME is a string or #f, and is the timezone name. Default is #f.

The DST-FLAG is a boolean, and indicates whether Day Saving TIme (or Summer Time) is active. Default is #f.

When the ZONE-OFFSET is a timezone-components object the TZ-NAME and DST-FLAG are pulled from the timezone-components, unless explicitly supplied.

read-leap-second-table

read-leap-second-table FILENAMEprocedure

Sets the leap second table from the specified FILENAME.

The file format is the same as the "tai-utc.dat" file in the distribution. Provided by the U.S. Naval Observatory.

leap-year?

leap-year? DATEprocedure

Does the specified DATE fall on a leap year?

The DATE may be a numeric year or a date object.

SRFI-18 Time

Note that the SRFI-18 identifiers time?, current-time, seconds->time, time->seconds, milliseconds->time, and time->milliseconds are in conflict with those of SRFI-19.

time->srfi-18-time

time->srfi-18-time TIMEprocedure: Converts a SRFI-19 time object to a SRFI-18 time object. The conversion is really only meaningful for time-duration, but any time-type is accepted.

srfi-18-time->time

srfi-18-time->time TIMEprocedure: Converts a SRFI-18 time object into a SRFI-19 time-duration object.

Object Printing

time-record-printer-format

time-record-printer-format #!optional FORMprocedure: FORM is 'srfi-10 or '#f.

date-record-printer-format

date-record-printer-format #!optional FORMprocedure: FORM is 'srfi-10 or '#f.

Time Conversion

seconds->time

(seconds->time SECONDS [TIME-TYPE time-duration]) -> timeprocedure: Converts a SECONDS value, may be fractional, into a TIME-TYPE time object.

seconds->date

(seconds->date SECONDS [TIMEZONE-INFO #t]) -> dateprocedure

Converts a SECONDS value, which may be fractional, into a date object. The TIMEZONE-INFO is #t for the local timezone, #f for the utc timezone, or a timezone-components object.

SECONDS is relative to 00:00:00 January 1, 1970 UTC.

time->nanoseconds

time->nanoseconds TIMEprocedure: Returns the TIME object value as a nanoseconds value.

nanoseconds->time

(nanoseconds->time NANOSECONDS [TIME-TYPE time-duration]) -> timeprocedure: Returns the NANOSECONDS value as a time TIME-TYPE object.

nanoseconds->seconds

nanoseconds->seconds NANOSECONDSprocedure: Returns the NANOSECONDS value as an inexact seconds value.

time->milliseconds

time->milliseconds TIMEprocedure: Returns the TIME object value as a milliseconds value.

milliseconds->time

(milliseconds->time MILLISECONDS [TIME-TYPE time-duration]) -> timeprocedure: Returns the MILLISECONDS value as a time TIME-TYPE object.

milliseconds->seconds

milliseconds->seconds MILLISECONDSprocedure: Returns the MILLISECONDS value as an inexact seconds value.

time->date

time->date TIMEprocedure: Returns the TIME object value as a date. A shorthand for the (time-*->date...) procedures.

time->julian-day

time->julian-day TIMEprocedure: Returns the julian day for the TIME object.

time->modified-julian-day

time->modified-julian-day TIMEprocedure: Returns the modified julian day for the TIME object.

Time Arithmetic

make-duration

(make-duration [#:days 0] [#:hours 0] [#:minutes 0] [#:seconds 0] [#:milliseconds 0] [#:microseconds 0] [#:nanoseconds 0]) -> timeprocedure: Returns a time-object of clock-type time-duration where the seconds and nanoseconds values are calculated by summing the keyword arguments.

zero-time

(zero-time [TIME-TYPE time-duration]) -> timeprocedure

TIME-FINE-GRAIN

Most minimum positive amount of time, as a duration.

divide-duration

divide-duration DURATION NUMBERprocedure: Returns a duration, from DURATION, divided by NUMBER, without remainder.

divide-duration!

divide-duration! DURATION NUMBERprocedure: Returns DURATION, divided by NUMBER, without remainder.

multiply-duration

multiply-duration DURATION NUMBERprocedure: Returns a duration, from DURATION, multiplied by NUMBER, truncated.

multiply-duration!

multiply-duration! DURATION NUMBERprocedure: Returns DURATION, multiplied by NUMBER, truncated.

time-negative?

time-negative? TIMEprocedure

Is TIME negative?

A time object will never have a negative nanoseconds value.

time-positve?

time-positve? TIMEprocedure: Is TIME positive?

time-zero?

time-zero? TIMEprocedure: Is TIME zero?

time-abs

time-abs TIMEprocedure: Returns the absolute time value, from TIME.

time-abs!

time-abs! TIMEprocedure: Returns the absolute TIME value.

time-negate

time-negate TIMEprocedure: Returns the sign inverted time value, from TIME.

time-negate!

time-negate! TIMEprocedure: Returns the TIME sign inverted value.

Time Comparison

time-compare

time-compare TIME1 TIME2procedure: Returns -1, 0, or 1.

time-max

time-max TIME1 #!optional TIME2...procedure: Returns the maximum time object from TIME1 TIME2....

time-min

time-min TIME1 #!optional TIME2...procedure: Returns the minimum time object from TIME1 TIME2....

Dates

default-date-clock-type

(default-date-clock-type [CLOCK-TYPE time-utc]) -> symbolparameter: Sets or gets the clock-type used by default for conversion of a date to a time.

copy-date

copy-date DATEprocedure: Returns an exact copy of the specified DATE object.

date->seconds

date->seconds DATE #!optional CLOCK-TYPE default-date-clock-typeprocedure

Returns the specified DATE as as an inexact seconds value, based on the CLOCK-TYPE.

The seconds value is relative to the TAI-EPOCH - 1 January 1970 CE at 00:00:00 UTC.

date->time

date->time DATE #!optional CLOCK-TYPE default-date-clock-typeprocedure: Returns the specified DATE as a time-object of type CLOCK-TYPE.

date-zone-name

date-zone-name DATEprocedure: Returns the timezone abbreviation of the specified DATE object. The result is either a string or #f.

date-dst?

date-dst? DATEprocedure

Returns the daylight saving time flag of the specified DATE object.

Only valid for "current" dates. Historical dates will not have a correct setting. Future dates cannot have a correct setting.

Date Arithmetic

date-difference

date-difference DATE1 DATE2 #!optional CLOCK-TYPEprocedure: Returns the time-duration between DATE1 and DATE2.

Returns a new date, the DATE adjusted by the AMOUNT of DATE-KEY.

AMOUNT is an integer.

DATE-KEY is either 'years, 'quarters, 'months, 'days, 'hours, 'minutes, 'seconds, 'milliseconds, 'microseconds, or 'nanoseconds.

If the day of the month of DATE is greater than the number of days in the final month, the day of the month will change to the last day in the final month.

Adjusting a time DATE-KEY (ex: 'hours) follows the semantics of date-add-duration.

Date Comparison

date-compare

date-compare DATE1 DATE2procedure: Returns -1, 0, or 1.

date=?

date=? DATE1 DATE2procedure: Is DATE1 on DATE2?

date>?

date>? DATE1 DATE2procedure: Is DATE1 after DATE2?

date<?

date<? DATE1 DATE2procedure: Is DATE1 before DATE2?

date>=?

date>=? DATE1 DATE2procedure: Is DATE1 after or on DATE2?

date<=?

date<=? DATE1 DATE2procedure: Is DATE1 before or on DATE2?

Timezone

Note that the daylight saving time (summer time) flag is always taken from the system, unless supplied. Any summer time rule component of a timezone-components object is not processed.

Remember that SRFI-19 timezone offset follows ISO 8601.

local-timezone-locale

local-timezone-locale #!optional TZ-COMPONENTSparameter: Gets or sets the local timezone-locale object.

utc-timezone-locale

utc-timezone-locale #!optional TZ-COMPONENTSparameter

Gets or sets the utc timezone-locale object.

Probably not a good idea to change the value.

timezone-locale-name

timezone-locale-name #!optional TZ-COMPONENTSprocedure: Returns the timezone-locale name of the supplied TZ-COMPONENTS, or the (local-timezone-locale) if missing.

timezone-locale-offset

timezone-locale-offset #!optional TZ-COMPONENTSprocedure: Returns the timezone-locale offset of the supplied TZ-COMPONENTS, or the (local-timezone-locale) if missing.

timezone-locale-dst?

timezone-locale-dst? #!optional TZ-COMPONENTSprocedure: Returns the timezone-locale daylight saving time flag of the supplied TZ-COMPONENTS, or the (local-timezone-locale) if missing.

Input/Output Procedures

(require-extension srfi-19-io)

DATE->STRING conversion specifiers

The SRFI-19 document does not mention the padding character override feature for the normally zero-padded conversions f, H, I, j, m, M, N, S, y. If the tilde is followed by a - then padding is suppressed. If followed by a _ the space character is used for padding. Otherwise zero-padding is perfomed, the default.

~[-_][fHIjmMNSy]

format-date

format-date DESTINATION DATE-FORMAT-STRING DATEprocedure

Displays a text form of the DATE on the DESTINATION using the DATE-FORMAT-STRING.

When the DESTINATION is #t the (current-output-port) is used, and the date object must be specified.

When the DESTINATION is a port it must be an output-port, and the date object must be specified.

When the DESTINATION is a number the (current-error-port) is the DESTINATION, and the DATE object must be specified.

When the DESTINATION is #f the result is returned as a string, and the DATE object must be specified.

format-date DATE-FORMAT-STRING DATEprocedure: Result is returned as a string.

scan-date

scan-date SOURCE TEMPLATE-STRINGprocedure

Reads a text form of a date from the SOURCE, following the TEMPLATE-STRING, and returns a date object.

When the SOURCE is #t the (current-input-port) is used.

When the SOURCE is a port it must be an input-port.

When the SOURCE is string it should be a date text form.

Time Period

Usage

(require-extension srfi-19-period)

A time-period is an interval, [begin end), where begin and end are time objects of the same clock type.

make-time-period

make-time-period BEGIN END #!optional CLOCK-TYPE default-date-clock-typeprocedure

Returns a new time-period object. The clock types must be compatible.

BEGIN maybe a seconds value, a date, or a time (except time-duration). A seconds value or date are converted to CLOCK-TYPE.

END maybe a seconds value, a date, or a time. A seconds value or date are converted to the same clock type as BEGIN. A time-duration is treated as an offset from BEGIN.

copy-time-period

copy-time-period TIME-PERIODprocedure: Returns a copy of TIME-PERIOD.

time-period-begin

time-period-begin TIME-PERIODprocedure: Returns the start time for the TIME-PERIOD.

time-period-end

time-period-end TIME-PERIODprocedure: Returns the end time for the TIME-PERIOD.

time-period-last

time-period-last TIME-PERIODprocedure: Returns the last time for the TIME-PERIOD; (time-period-end - TIME-FINE-GRAIN).

time-period-type

time-period-type TIME-PERIODprocedure: Returns the clock-type of the TIME-PERIOD.

time-period?

time-period? OBJECTprocedure: Is OBJECT a time-period?

time-period-length

time-period-length TIME-PERIODprocedure: Returns the time-duration of the TIME-PERIOD.

time-period-compare

time-period-compare TIME-PERIOD-1 TIME-PERIOD-2procedure: Returns -1 when TIME-PERIOD-1 < TIME-PERIOD-2, 0 when TIME-PERIOD-1 = TIME-PERIOD-2 and 1 TIME-PERIOD-1 > TIME-PERIOD-2.

time-period=?

time-period=? TIME-PERIOD-1 TIME-PERIOD-2procedure: Does TIME-PERIOD-1 begin & end with TIME-PERIOD-2?

time-period<?

time-period<? TIME-PERIOD-1 TIME-PERIOD-2procedure: Does TIME-PERIOD-1 end before TIME-PERIOD-2 begins?

time-period>?

time-period>? TIME-PERIOD-1 TIME-PERIOD-2procedure: Does TIME-PERIOD-1 begin after TIME-PERIOD-2 ends?

time-period<=?

time-period<=? TIME-PERIOD-1 TIME-PERIOD-2procedure: Does TIME-PERIOD-1 end on or before TIME-PERIOD-2 begins?

time-period>=?

time-period>=? TIME-PERIOD-1 TIME-PERIOD-2procedure: Does TIME-PERIOD-1 begin on or after TIME-PERIOD-2 ends?

time-period-preceding

time-period-preceding TIME-PERIOD-1 TIME-PERIOD-2procedure: Return the portion of TIME-PERIOD-1 before TIME-PERIOD-2 or #f when it doesn't precede.

time-period-succeeding

time-period-succeeding TIME-PERIOD-1 TIME-PERIOD-2procedure: Return the portion of TIME-PERIOD-1 after TIME-PERIOD-2 or #f when it doesn't succeed.

time-period-contains/period?

time-period-contains/period? TIME-PERIOD-1 TIME-PERIOD-2procedure: Is TIME-PERIOD-2 within TIME-PERIOD-1?

time-period-contains/time?

time-period-contains/time? TIME-PERIOD TIMEprocedure

Is TIME within TIME-PERIOD?

TIME is converted to a compatible clock-type if possible.

time-period-contains/date?

time-period-contains/date? TIME-PERIOD DATEprocedure

Is DATE within TIME-PERIOD?

DATE is converted to a compatible time if possible.

time-period-contains?

time-period-contains? TIME-PERIOD OBJECTprocedure

Is OBJECT within TIME-PERIOD?

OBJECT maybe a time, date, or time-period.

time-period-intersects?

time-period-intersects? TIME-PERIOD-1 TIME-PERIOD-2procedure: Does TIME-PERIOD-2 overlap TIME-PERIOD-1?

time-period-intersection

time-period-intersection TIME-PERIOD-1 TIME-PERIOD-2procedure: The overlapping time-period of TIME-PERIOD-2 and TIME-PERIOD-1, or #f when no overlap.

time-period-union

time-period-union TIME-PERIOD-1 TIME-PERIOD-2procedure: Returns the time-period spanned by TIME-PERIOD-1 and TIME-PERIOD-2, or #f when they do not intersect.

time-period-span

time-period-span TIME-PERIOD-1 TIME-PERIOD-2procedure: Returns the time-period spanned by TIME-PERIOD-1 and TIME-PERIOD-2, including any gaps.

time-period-shift

time-period-shift TIME-PERIOD DURATIONprocedure: Returns a copy of TIME-PERIOD shifted by DURATION.

time-period-shift!

time-period-shift! TIME-PERIOD DURATIONprocedure: Returns TIME-PERIOD shifted by DURATION.

Usage

This module exports the time, date, timezone, and io APIs.

(require-extension srfi-19)

Examples

Prevent default timezone initialization by explicitly setting the 'timezone.

;must be done before 1st invocation of a srfi-19 export
(use locale)
(set-locale-category! 'timezone
  (posix-timezone-string->timezone-components
    ;some acceptable posix tz form
    "XSX+2:00XDX+1:00:00"
    ;source of tz info
    '("POSIX" "TZ")))

;now we can use srfi-19 in our runtime tz
(use srfi-19 extras)
(format #t "Present Day: ~A~%Present Time: ~A~%: Hah, hah, hah.~%"
  (current-date) (current-time))

Notes

The string->date and scan-date procedures will not create an incomplete date. At a minimum the input must include day, month and year components; the time and timezone components default to 0 and the locale, respectively.
31 December 1 BCE + 1 day -> 1 January 1 CE. There is no year 0. Unlike the ISO 8601 convention do not subtract 1 when converting a year BCE to a SRFI-19 year, just negate the year.
The SRFI-18 current-time and time? bindings conflict with SRFI-19 bindings.
A SRFI-18 time object is not accepted except by the conversion procedures.
The expression (time=? (seconds->time (nanoseconds->seconds (time->nanoseconds <time-duration>))) <time-duration>) might be #f, due to the use of inexact arithmetic.
Be careful using the procedures that return some form of 'julian-day'. These are implemented using the full numeric tower and will return rational numbers. Performing arithmetic with such a result will require the "numbers" egg. See the file "srfi-19-test.scm" in this egg for an example. This will be a problem with code that assumes fixnum and/or flonum only numbers. Perhaps an intermediate file that wraps any 'julian-day' calls and coerces to an inexact number. Use the wrapped 'julian-day' call in the problematic code.

Bugs and Limitations

Local timezone information is not necessarily valid for historic dates and problematic for future dates. Daylight saving time is especially an issue. Conversion of a time or seconds value to a local date will use the current timezone offset value. The current offset will reflect the daylight saving time status. So target dates outside of the DST period will be converted incorrectly!
Will not read years less than 1 properly. The ISO 8601 year convention for years 1 BCE and before and years 10000 CE and after is not supported.
Cannot swap SRFI 29 bundle. Fixed at load time.
Using date-adjust for the same date-key MomentJS says:

If you are adding hours, minutes, seconds, or milliseconds, the assumption is that you want precision to the hour, and will result in a different hour.

var m = moment(new Date(2011, 2, 12, 5, 0, 0)); // the day before DST in the US
m.hours(); // 5
m.add(24, 'hours').hours(); // 6

but this implementation says 1 day = 24 hours, so same hour.

Requirements

locale srfi-29 miscmacros numbers check-errors record-variants

Author

Kon Lovett

Version history

3.7.0: Added date->seconds.
3.6.0: Delay locale initialization.
3.5.0: Document time-record-printer-format & date-record-printer-format.
3.4.3: Fix #1000(?).
3.4.2: .
3.4.1: fix nanosecond squared value in date
3.4.0: add TIME-FINE-GRAIN, generalize make-time, add date-adjust.
3.3.6: Update leap second table.
3.3.5
3.3.4: Fix for ticket #630.
3.3.3: Fix for weekday name indexing, ticket #966.
3.3.2: Fix for removed ##sys#double->number.
3.3.1: Fix for time-monotonic->julian-day return, ticket #829.
3.3.0: Uses compiled setup-helper-mod.
3.2.0: Removed null time-period.
3.1.2: Fix for flonum (current-milliseconds). Fix for date-add/subtract-duration (actually time->date support for date-timezone-info). [Reported by Thomas Hintz]
3.1.1: Bug fix for non-unique month name key for May. Added padding character override information. The ZONE-OFFSET argument of make-date is optional. Added German bundle by Moritz Heidkamp.
3.1.0: Use of record-variants extension.
3.0.3: Bug fix for missing seconds->time & seconds->date in srfi-19. (Reported by Alex Suraci)
3.0.2: Bug fix for format-date output port check, format-date and scan-date argument type checks.
3.0.1: Bug fix for ~y input conversion.
3.0.0: Initial Chicken 4 release

License

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the Software), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED ASIS, WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

This document and translations of it may be copied and furnished to others, and derivative works that comment on or otherwise explain it or assist in its implementation may be prepared, copied, published and distributed, in whole or in part, without restriction of any kind, provided that the above copyright notice and this paragraph are included on all such copies and derivative works. However, this document itself may not be modified in any way, such as by removing the copyright notice or references to the Scheme Request For Implementation process or editors, except as needed for the purpose of developing SRFIs in which case the procedures for copyrights defined in the SRFI process must be followed, or as required to translate it into languages other than English.

The limited permissions granted above are perpetual and will not be revoked by the authors or their successors or assigns.

This document and the information contained herein is provided on an "AS IS" basis and THE AUTHOR AND THE SRFI EDITORS DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.

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