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Fix description of Unix time, mention new function.

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* lisp/calc/calc-forms.el (calcFunc-unixtime): Fix adjustment for
Unix time.
* doc/misc/calc.texi (Date Forms): Fix description of Unix time.
(Basic Operations on Units): Mention `calc-convert-exact-units'.
This commit is contained in:
Jay Belanger 2015-04-09 19:03:19 -05:00
parent c1daad42c6
commit e368697ce3
2 changed files with 16 additions and 22 deletions
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34
doc/misc/calc.texi
View file

@ -11098,12 +11098,12 @@ noon GMT@.) Julian day numbering is largely used in astronomy.
@cindex Unix time format
The Unix operating system measures time as an integer number of
seconds since midnight, Jan 1, 1970. To convert a Calc date
value into a Unix time stamp, first subtract 719164 (the code
value into a Unix time stamp, first subtract 719163 (the code
for @samp{<Jan 1, 1970>}), then multiply by 86400 (the number of
seconds in a day) and press @kbd{R} to round to the nearest
integer. If you have a date form, you can simply subtract the
day @samp{<Jan 1, 1970>} instead of unpacking and subtracting
719164. Likewise, divide by 86400 and add @samp{<Jan 1, 1970>}
719163. Likewise, divide by 86400 and add @samp{<Jan 1, 1970>}
to convert from Unix time to a Calc date form. (Note that
Unix normally maintains the time in the GMT time zone; you may
need to subtract five hours to get New York time, or eight hours
@ -27860,14 +27860,20 @@ while typing @kbd{u c au/yr @key{RET}} produces
If the units you request are inconsistent with the original units, the
number will be converted into your units times whatever ``remainder''
units are left over. (This can be disabled; @pxref{Customizing Calc}.)
For example, converting @samp{55 mph} into acres
produces @samp{6.08e-3 acre / m s}. (Recall that multiplication binds
more strongly than division in Calc formulas, so the units here are
acres per meter-second.) Remainder units are expressed in terms of
units are left over. For example, converting @samp{55 mph} into acres
produces @samp{6.08e-3 acre / (m s)}. Remainder units are expressed in terms of
``fundamental'' units like @samp{m} and @samp{s}, regardless of the
input units.
@kindex u n
@pindex calc-convert-exact-units
If you intend that your new units be consistent with the original
units, the @kbd{u n} (@code{calc-convert-exact-units}) command will
check the units before the conversion. For example, to change
@samp{mi/hr} to @samp{km/hr}, you could type @kbd{u c km @key{RET}},
but @kbd{u n km @key{RET}} would signal an error.
You would need to type @kbd{u n km/hr @key{RET}}.
One special exception is that if you specify a single unit name, and
a compatible unit appears somewhere in the units expression, then
that compatible unit will be converted to the new unit and the
@ -35684,19 +35690,6 @@ as @samp{a/(b*c)}. If @code{calc-multiplication-has-precedence} is
of @code{calc-multiplication-has-precedence} is @code{t}.
@end defvar
@defvar calc-ensure-consistent-units
When converting units, the variable @code{calc-ensure-consistent-units}
determines whether or not the target units need to be consistent with the
original units. If @code{calc-ensure-consistent-units} is @code{nil}, then
the target units don't need to have the same dimensions as the original units;
for example, converting @samp{100 ft/s} to @samp{m} will produce @samp{30.48 m/s}.
If @code{calc-ensure-consistent-units} is non-@code{nil}, then the target units
need to have the same dimensions as the original units; for example, converting
@samp{100 ft/s} to @samp{m} will result in an error, since @samp{ft/s} and @samp{m}
have different dimensions. The default value of @code{calc-ensure-consistent-units}
is @code{nil}.
@end defvar
@defvar calc-context-sensitive-enter
The commands @code{calc-enter} and @code{calc-pop} will typically
duplicate the top of the stack. If
@ -36497,6 +36490,7 @@ keystrokes are not listed in this summary.
@r{ defn@: u d @:unit, descr @: @:calc-define-unit@:}
@r{ @: u e @: @: @:calc-explain-units@:}
@r{ @: u g @:unit @: @:calc-get-unit-definition@:}
@r{ @: u n @:units @: 18 @:calc-convert-exact-units@:}
@r{ @: u p @: @: @:calc-permanent-units@:}
@r{ a@: u r @: @: @:calc-remove-units@:}
@r{ a@: u s @: @: @:usimplify@:(a)}

4
lisp/calc/calc-forms.el
View file

@ -1438,11 +1438,11 @@ as measured in the integer number of days before December 31, 1 BC (Gregorian)."
(defun calcFunc-unixtime (date &optional zone)
(if (math-realp date)
(progn
(setq date (math-add 719164 (math-div date '(float 864 2))))
(setq date (math-add 719163 (math-div date '(float 864 2))))
(list 'date (math-sub date (math-div (calcFunc-tzone zone date)
'(float 864 2)))))
(if (eq (car date) 'date)
(math-add (nth 1 (math-date-parts (nth 1 date) 719164))
(math-add (nth 1 (math-date-parts (nth 1 date) 719163))
(calcFunc-tzone zone date))
(math-reject-arg date 'datep))))