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ADDED: format_time//2 for describing strings involving dates and times

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current_time/1 yields the current system time as an opaque time stamp.
This commit is contained in:
Markus Triska
2020-06-10 23:13:14 +02:00
parent e16762a137
commit 2fc887724b
5 changed files with 88 additions and 9 deletions
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src/prolog/lib/time.pl
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@@ -1,19 +1,73 @@
/* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
Written April 2020 by Markus Triska (triska@metalevel.at)
Written 2020 by Markus Triska (triska@metalevel.at)
Part of Scryer Prolog.
This library provides predicates for reasoning about time.
Reasoning about time stamps would be a useful addition, for example
by obtaining the current time, comparing and formatting it.
'$cpu_now' can be replaced by statistics/2 once that is implemented.
current_time(T) yields the current system time in an opaque form,
called a time stamp. Use format_time//2 to describe strings that
contain attributes of the time stamp.
The nonterminal format_time//2 describes a list of characters that
are formatted according to a format string. Usage:
phrase(format_time(FormatString, TimeStamp), Cs)
TimeStamp represents a moment in time in an opaque form, as for
example obtained by current_time/1.
FormatString is a list of characters that are interpreted literally,
except for the following specifiers (and possibly more in the future):
%Y year of the time stamp. Example: 2020.
%m month number (01-12), zero-padded to 2 digits
%d day number (01-31), zero-padded to 2 digits
%H hour number (00-24), zero-padded to 2 digits
%M minute number (00-59), zero-padded to 2 digits
%S second number (00-60), zero-padded to 2 digits
%b abbreviated month name, always 3 letters
%a abbreviated weekday name, always 3 letters
%A full weekday name
%j day of the year (001-366), zero-padded to 3 digits
%% the literal %
Example:
?- current_time(T), phrase(format_time("%d.%m.%Y (%H:%M:%S)", T), Cs).
T = [...], Cs = "11.06.2020 (00:24:32)"
; false.
sleep(S) sleeps for S seconds (a floating point number).
time(Goal) reports the execution time of Goal.
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
:- module(time, [max_sleep_time/1, sleep/1, time/1]).
:- module(time, [max_sleep_time/1, sleep/1, time/1, current_time/1, format_time//2]).
:- use_module(library(format)).
:- use_module(library(iso_ext)).
:- use_module(library(error)).
:- use_module(library(dcgs)).
:- use_module(library(lists)).
:- use_module(library(charsio), [read_term_from_chars/2]).
current_time(T) :-
'$current_time'(T0),
read_term_from_chars(T0, T).
format_time([], _) --> [].
format_time(['%','%'|Fs], T) --> !, "%", format_time(Fs, T).
format_time(['%',Spec|Fs], T) --> !,
( { member(Spec=Value, T) } ->
list(Value)
; { domain_error(time_specifier, Spec, format_time//2) }
),
format_time(Fs, T).
format_time([F|Fs], T) --> [F], format_time(Fs, T).
list([]) --> [].
list([L|Ls]) --> [L], list(Ls).
max_sleep_time(0xfffffffffffffbff).
@@ -26,6 +80,9 @@ sleep(T) :-
; '$sleep'(T)
).
% '$cpu_now' can be replaced by statistics/2 once that is implemented.
time(Goal) :-
'$cpu_now'(T0),
setup_call_cleanup(true,