%D \module
%D   [       file=phys-dim,
%D        version=2011-06-13, % was digits and units 1997.03.19,
%D          title=\CONTEXT\ Physics,
%D       subtitle=Digits and Units,
%D         author={Hans Hagen},
%D           date=\currentdate,
%D      copyright={PRAGMA ADE \& \CONTEXT\ Development Team}]
%C
%C This module is part of the \CONTEXT\ macro||package and is
%C therefore copyrighted by \PRAGMA. See mreadme.pdf for
%C details.

\registerctxluafile{phys-dim}{}

% TAGGING NEEDS CHECKING ... WILL DO WHEN PARSER IS OK

\unprotect

%D \macros
%D   {digits, setdigitmode, setdigitsign}
%D
%D This is an update of the \MKII\ digits mechanism. Beware,
%D space delimited mode is now resticted!
%D
%D Depending on the digit mode the command \type {\digits}
%D normalizes number patterns depending on the language set.
%D
%D \starttyping
%D This will never be a \digits{1.000.000} seller.
%D \stoptyping
%D
%D We still support the space delimited case but this is only for special
%D purposes. When used in the text, you'd better use the argument variant.
%D
%D \startbuffer
%D 1 \setdigitmode {1} \setdigitorder{0} \digits {12.345,90}
%D 2 \setdigitmode {2} \setdigitorder{0} \digits {12.345,90}
%D 3 \setdigitmode {3} \setdigitorder{0} \digits {12.345,90}
%D 4 \setdigitmode {4} \setdigitorder{0} \digits {12.345,90}
%D 5 \setdigitmode {5} \setdigitorder{0} \digits {12.345,90}
%D 6 \setdigitmode {6} \setdigitorder{0} \digits {12.345,90}
%D 1 \setdigitmode {1} \setdigitorder{1} \digits {12.345,90}
%D 2 \setdigitmode {2} \setdigitorder{1} \digits {12.345,90}
%D 3 \setdigitmode {3} \setdigitorder{1} \digits {12.345,90}
%D 4 \setdigitmode {4} \setdigitorder{1} \digits {12.345,90}
%D 5 \setdigitmode {5} \setdigitorder{1} \digits {12.345,90}
%D 6 \setdigitmode {6} \setdigitorder{1} \digits {12.345,90}
%D \stopbuffer
%D
%D \typebuffer
%D
%D This is typeset as:
%D
%D \startlines \getbuffer \stoplines
%D
%D The sign can be typeset as is or within the space of a
%D digit.
%D
%D \startbuffer
%D \setdigitsign 0 \digits {+12.345,90}
%D \setdigitsign 1 \digits {+12.345,90}
%D \stopbuffer
%D
%D \typebuffer
%D
%D This is typset as:
%D
%D \startlines
%D \getbuffer
%D \stoplines
%D
%D The digit modes are:
%D
%D \startitemize[n,packed]
%D \item periods/comma
%D \item commas/period
%D \item thinmuskips/comma
%D \item thinmuskips/period
%D \item thickmuskips/comma
%D \item thickmuskips/period
%D \stopitemize
%D
%D The digit parser handles a bunch of special characters as
%D well as different formats. We strongly suggest you to use
%D the grouped call.
%D
%D \starttabulate[|l|l|l|]
%D \starttabulate[|l|l|l|]
%D \NC \type{.}  \NC , .           \NC comma or period     \NC \NR
%D \NC \type{,}  \NC , .           \NC comma or period     \NC \NR
%D \NC \type{:}  \NC               \NC invisible period    \NC \NR
%D \NC \type{;}  \NC               \NC invisible comma     \NC \NR
%D \NC \type{_}  \NC               \NC invisible space     \NC \NR
%D \NC \type{/}  \NC               \NC invisible sign      \NC \NR
%D \NC \type{-}  \NC $-$           \NC minus sign          \NC \NR
%D \NC \type{+}  \NC $+$           \NC plus sign           \NC \NR
%D \NC \type{//} \NC               \NC invisible high sign \NC \NR
%D \NC \type{--} \NC $\negative$   \NC high minus sign     \NC \NR
%D \NC \type{++} \NC $\positive$   \NC high plus sign      \NC \NR
%D \NC \type{=}  \NC $\zeroamount$ \NC zero padding        \NC \NR
%D \stoptabulate
%D \stoptabulate
%D
%D These triggers are used in the following examples.
%D
%D \starttabulate[|l|r|]
%D \NC \type{1}                      \NC \ruledhbox{\strut\digits{1}}                      \NC \NR
%D \NC \type{12}                     \NC \ruledhbox{\strut\digits{12}}                     \NC \NR
%D \NC \type{12.34}                  \NC \ruledhbox{\strut\digits{12.34}}                  \NC \NR
%D \NC \type{123,456}                \NC \ruledhbox{\strut\digits{123,456}}                \NC \NR
%D \NC \type{123,456.78}             \NC \ruledhbox{\strut\digits{123,456.78}}             \NC \NR
%D \NC \type{12,34}                  \NC \ruledhbox{\strut\digits{12,34}}                  \NC \NR
%D \NC \type{.1234}                  \NC \ruledhbox{\strut\digits{.1234}}                  \NC \NR
%D \NC \type{1234}                   \NC \ruledhbox{\strut\digits{1234}}                   \NC \NR
%D \NC \type{123,456.78^9}           \NC \ruledhbox{\strut\digits{123,456.78^9}}           \NC \NR
%D \NC \type{123,456.78e9}           \NC \ruledhbox{\strut\digits{123,456.78e9}}           \NC \NR
%D \NC \type{/123,456.78e-9}         \NC \ruledhbox{\strut\digits{/123,456.78e-9}}         \NC \NR
%D \NC \type{-123,456.78e-9}         \NC \ruledhbox{\strut\digits{-123,456.78e-9}}         \NC \NR
%D \NC \type{+123,456.78e-9}         \NC \ruledhbox{\strut\digits{+123,456.78e-9}}         \NC \NR
%D \NC \type{//123,456.78e-9}        \NC \ruledhbox{\strut\digits{//123,456.78e-9}}        \NC \NR
%D \NC \type{--123,456.78e-9}        \NC \ruledhbox{\strut\digits{--123,456.78e-9}}        \NC \NR
%D \NC \type{++123,456.78e-9}        \NC \ruledhbox{\strut\digits{++123,456.78e-9}}        \NC \NR
%D \NC \type{___,___,123,456,789.00} \NC \ruledhbox{\strut\digits{___,___,123,456,789.00}} \NC \NR
%D \NC \type{___,___,_12,345,678.==} \NC \ruledhbox{\strut\digits{___,___,_12,345,678.==}} \NC \NR
%D \stoptabulate

\newconstant\c_phys_digits_order
\newconstant\c_phys_digits_method
\newconstant\c_phys_digits_sign  % we has sized (text script scriptscript)

\unexpanded\def\setdigitmethod#1{\c_phys_digits_method #1\relax}
\unexpanded\def\setdigitsign  #1{\c_phys_digits_sign   #1\relax}
\unexpanded\def\setdigitorder #1{\c_phys_digits_order  #1\relax}

\let\setdigitmode\setdigitmethod % compatibility

\def\phys_digits_normalized % we could calculate once and remember
  {\ifcase\c_phys_digits_sign
     \expandafter\secondoftwoarguments
   \else\ifmmode
     \expandafter\expandafter\expandafter\phys_digits_normalized_math
   \else
     \expandafter\expandafter\expandafter\phys_digits_normalized_text
   \fi\fi}

\def\phys_digits_normalized_math#1#2%
  {\setbox\scratchbox\hbox{$\Ustack{#1}$}%
   \hbox to \wd\scratchbox{\hss{$\Ustack{#2}$}\hss}}

\def\phys_digits_normalized_text#1#2%
  {\setbox\scratchbox\hbox{#1}%
   \hbox to \wd\scratchbox{\hss#2\hss}}

\def\phys_digits_raised
  {\ifmmode
     \expandafter\normalsuperscript
   \else
     \expandafter\unitshigh
   \fi}

% we could use a symbolset but how many symbols are there ?

% \definesymbol[units][times][\times]
% \definesymbol[units][times][\cdots]

% \def\digitstimessymbol{\symbol[units][times]}

% \definesymbol[units][times][\times]
% \definesymbol[units][times][\cdots]
% \definesymbol[units][times][\ifmmode\cdot\else\kern.2\emwidth\cdot\kern.2\emwidth\fi]

\unexpanded\def\digitstextbinop#1% assumes preceding
  {\fourperemspace\nobreak\times\fourperemspace}

%def\digitstimessymbol{\ifmmode\cdot\else\digitstextbinop\cdot\fi}
\def\digitstimessymbol{\ifmmode\times\else\digitstextbinop\times\fi}

\unexpanded\def\digitszeropadding   {\hphantom{0}}
\unexpanded\def\digitsnegative      {\phys_digits_normalized{0}{\phys_digits_raised{\textminus}}}
\unexpanded\def\digitspositive      {\phys_digits_normalized{0}{\phys_digits_raised{\textplus}}}
\unexpanded\def\digitsnegative      {\phys_digits_normalized{0}{\mathematics{\negative}}}
\unexpanded\def\digitspositive      {\phys_digits_normalized{0}{\mathematics{\positive}}}
%unexpanded\def\digitsminus         {\phys_digits_normalized{0}{\mathematics{-}}}
%unexpanded\def\digitsplus          {\phys_digits_normalized{0}{\mathematics{+}}}
\unexpanded\def\digitsminus         {\phys_digits_normalized{0}{\mathminus}}
\unexpanded\def\digitsplus          {\phys_digits_normalized{0}{\mathplus }}
\unexpanded\def\digitsspace         {\hphantom{0}}
\unexpanded\def\digitsseparatorspace{\hphantom{.}}
\unexpanded\def\digitssignspace     {\hphantom{\digitsminus}}
\unexpanded\def\digitshighspace     {\hphantom{\digitspositive}}
\unexpanded\def\digitspower       #1{\digitstimessymbol10\phys_digits_raised{#1}}
\unexpanded\def\digitspowerplus   #1{\digitstimessymbol10\phys_digits_raised{\digitsplus#1}}
\unexpanded\def\digitspowerminus  #1{\digitstimessymbol10\phys_digits_raised{\digitsminus#1}}
\unexpanded\def\digitsdigit       #1{#1}

\unexpanded\def\normaldigitscommasymbol {,}
\unexpanded\def\normaldigitsperiodsymbol{.}

\let\normaldigitsseparatorspace\digitsseparatorspace

\installcorenamespace{digitscomma}
\installcorenamespace{digitsperiod}
\installcorenamespace{digitsspace}

\letvalue{\??digitscomma 0}\normaldigitscommasymbol
\letvalue{\??digitsperiod0}\normaldigitsperiodsymbol
\letvalue{\??digitsspace 0}\normaldigitsseparatorspace

\letvalue{\??digitscomma 1}\normaldigitsperiodsymbol
\letvalue{\??digitsperiod1}\normaldigitscommasymbol
\letvalue{\??digitsspace 1}\normaldigitsseparatorspace

\letvalue{\??digitscomma 2}\normaldigitscommasymbol
\letvalue{\??digitsperiod2}\normaldigitsperiodsymbol
\letvalue{\??digitsspace 2}\normaldigitsseparatorspace

\letvalue{\??digitscomma 3}\thinspace
\letvalue{\??digitsperiod3}\normaldigitscommasymbol
\letvalue{\??digitsspace 3}\thinspace

\letvalue{\??digitscomma 4}\thinspace
\letvalue{\??digitsperiod4}\normaldigitsperiodsymbol
\letvalue{\??digitsspace 4}\thinspace

\letvalue{\??digitscomma 5}\thickspace
\letvalue{\??digitsperiod5}\normaldigitscommasymbol
\letvalue{\??digitsspace 5}\thickspace

\letvalue{\??digitscomma 6}\thickspace
\letvalue{\??digitsperiod6}\normaldigitsperiodsymbol
\letvalue{\??digitsspace 6}\thickspace

\unexpanded\def\digitscommasymbol         {\csname\??digitscomma \number\c_phys_digits_method\endcsname}
\unexpanded\def\digitsperiodsymbol        {\csname\??digitsperiod\number\c_phys_digits_method\endcsname}
\unexpanded\def\digitsseparatorspace      {\csname\??digitsspace \number\c_phys_digits_method\endcsname}

% \unexpanded\def\digitsfinalcomma          {\digitscommasymbol } % more for tracing
% \unexpanded\def\digitsfinalperiod         {\digitsperiodsymbol} % more for tracing
% \unexpanded\def\digitsintermediatecomma   {\digitscommasymbol } % more for tracing
% \unexpanded\def\digitsintermediateperiod  {\digitsperiodsymbol} % more for tracing

\unexpanded\def\digitsfinalcomma          {\digitsperiodsymbol} % more for tracing
\unexpanded\def\digitsfinalperiod         {\digitsperiodsymbol} % more for tracing
\unexpanded\def\digitsintermediatecomma   {\digitscommasymbol } % more for tracing
\unexpanded\def\digitsintermediateperiod  {\digitscommasymbol } % more for tracing

%D The user macro:

\unexpanded\def\phys_digits_indeed#1%
  {\dontleavehmode
   \begingroup
   \ifcase\c_phys_digits_order\expandafter\clf_digits_normal\else\expandafter\clf_digits_reverse\fi{\detokenize{#1}}%
   \endgroup
   \settrue\c_phys_units_dospace}

\unexpanded\def\digits
  {\doifelsenextbgroup\phys_digits_argument\phys_digits_spaced}

\def\phys_digits_argument#1%
  {\phys_digits_indeed{#1}}

\def\phys_digits_spaced#1 % space delimited
  {\phys_digits_indeed{#1}}

%D \macros
%D   {unit}
%D
%D We have been using the units module (and its predecessor) for over a decade
%D now but when we moved on to \LUATEX\ a variant was prototyped that permits a
%D less texie coding. I finally picked up that thread and cleaned up the code a
%D bit so users can now play with it. (The main reason was that I wanted to
%D test exporting.)
%D
%D \startbuffer
%D 01: $10\unit{km/h}$
%D 02: $\unit{10      km/h}$
%D 03: \unit{km/h}
%D 04: \unit{10 km/h}
%D 05: \unit{10 km/h}
%D 06: \unit{~1 km/h}
%D 07: 10\unit{km/h}
%D 08: 10 \unit{km/h}
%D 09: $10 \unit{km/h}$
%D 10: 10 \unit{KiloMeter/Hour}
%D 11: 10 \unit{kilometer/hour}
%D 12: 10 \unit{km/h}
%D 13: 10 \unit{kilometer per hour}
%D 14: 10 \unit{km / h}
%D 15: 10 \unit{ km / h }
%D 16: 10 \unit{km/ms2}
%D 17: 10 \unit{meter per second}
%D 18: 10 \unit{cubic meter}
%D 19: 10 \unit{cubic meter per second}
%D 21: 10 \unit{cubic meter / second}
%D 22: $10 \unit{cubic meter / second}$
%D 23: 30 \unit{kilo pascal }
%D 24: 30 \unit{kilo pascal square meter / second}
%D 25: 30 \unit{kilo pascal square meter / kelvin second}
%D 26: \unit{30 kilo pascal square meter / kelvin second}
%D 27: $30 \unit{kilo pascal square meter / kelvin second }$
%D 28: 30 \unit{crap}
%D 29: 30 \unit{AC}
%D 30: $\frac{10 \unit{m/s}}{20 \unit{m/s}} $
%D 31: {\ss 30 \unit{kilo pascal square meter / second kelvin}}
%D 32: \unit{123.22^-3 km/s}
%D 33: \unit{123.22e-3 km/s}
%D \stopbuffer
%D
%D \typebuffer
%D
%D Result: \startlines \getbuffer \stoplines
%D
%D Depending on needs we can add more tweaks (also depends on to what
%D extent we need to be compatible with \MKII.
%D
%D Formatting is supported too:
%D
%D \startbuffer
%D \starttabulate[|l|l|l|]
%D \HL
%D \NC \unit{10 kilo gram}       \NC \digits{10}        \NC \unit{10}        \NC \NR
%D \NC \unit{1 kilogram}         \NC \digits{1}         \NC \unit{1}         \NC \NR
%D \NC \unit{0.1 kilogram}       \NC \digits{0.1}       \NC \unit{0.1}       \NC \NR
%D \NC \unit{1.1 kilogram}       \NC \digits{1.1}       \NC \unit{1.1}       \NC \NR
%D \NC \unit{11 kilogram}        \NC \digits{11}        \NC \unit{11}        \NC \NR
%D \HL
%D \NC \unit{00,000.10 kilogram} \NC \digits{00,000.10} \NC \unit{00,000.10} \NC \NR
%D \NC \unit{@@,@@0.10 kilogram} \NC \digits{@@,@@0.10} \NC \unit{@@,@@0.10} \NC \NR
%D \NC \unit{__,___.10 kilogram} \NC \digits{__,___.10} \NC \unit{__,___.10} \NC \NR
%D \NC \unit{__,__0:10 kilogram} \NC \digits{__,__0:10} \NC \unit{__,__0:10} \NC \NR
%D \NC \unit{__,___:10 kilogram} \NC \digits{__,___:10} \NC \unit{__,___:10} \NC \NR
%D \HL
%D \stoptabulate
%D \stopbuffer
%D
%D \typebuffer \getbuffer
%D
%D Punctuation can be configures usiing \type {method}:
%D
%D \startbuffer
%D \starttabulate[|l|l|l|]
%D \HL
%D \NC   \NC \setupunits[method=0]\unit{00,000.10 kilogram} \NC \setupunits[method=0]\unit{@@,@@0.10 kilogram} \NC \NR
%D \NC 1 \NC \setupunits[method=1]\unit{00,000.10 kilogram} \NC \setupunits[method=1]\unit{@@,@@0.10 kilogram} \NC \NR
%D \NC 2 \NC \setupunits[method=2]\unit{00,000.10 kilogram} \NC \setupunits[method=2]\unit{@@,@@0.10 kilogram} \NC \NR
%D \NC 3 \NC \setupunits[method=3]\unit{00,000.10 kilogram} \NC \setupunits[method=3]\unit{@@,@@0.10 kilogram} \NC \NR
%D \NC 4 \NC \setupunits[method=4]\unit{00,000.10 kilogram} \NC \setupunits[method=4]\unit{@@,@@0.10 kilogram} \NC \NR
%D \NC 5 \NC \setupunits[method=5]\unit{00,000.10 kilogram} \NC \setupunits[method=5]\unit{@@,@@0.10 kilogram} \NC \NR
%D \NC 6 \NC \setupunits[method=6]\unit{00,000.10 kilogram} \NC \setupunits[method=6]\unit{@@,@@0.10 kilogram} \NC \NR
%D \HL
%D \stoptabulate
%D \stopbuffer
%D
%D \typebuffer \getbuffer

% only a space when a number is part of the unit

\installcorenamespace {unit}
\installcorenamespace {unitseparator}
\installcorenamespace {unitspace}

\installcommandhandler \??unit {unit} \??unit

\setupunit
  [\c!alternative=,              % done: text
   \c!separator=\v!normal,       % done: cdot|big|medium|space
   \s!language=\currentlanguage, % done: (no interface yet)
   \c!order=\v!normal,           % ,. (reverse: .,)
   \c!method=0,
  %\c!grid=\v!yes,               % (maybe)
  %\c!style=...,                 % done
  %\c!color=...,                 % done
  %\c!space=...,                 % (maybe) small medium big
  ]

\definehigh[unitshigh][\c!style=\txx]
\definelow [unitslow] [\c!style=\txx]

\let\setupunits\setupunit

\newconstant   \c_phys_units_mode   % 0=text 1=math 2=textinmath 3=mathintext
\newconstant   \c_phys_units_state  % 0=start 1=suffix 2=operator 3=unit 4=prefix 5=number
\newconditional\c_phys_units_quantity
\newconditional\c_phys_units_number
\newconditional\c_phys_units_dospace

% [\unit   {micro ohm}]\par %  no space before unit
% [10\unit {micro ohm}]\par %  no space before unit
% [10 \unit{micro ohm}]\par %     space before unit
% [ \unit  {micro ohm}]\par %     space before unit
% [\unit{10 micro ohm}]\par %     space before unit

\unexpanded\def\unitssmallspace {\thinspace}
\unexpanded\def\unitsmediumspace{\medspace}
\unexpanded\def\unitsbigspace   {\thickspace}
\unexpanded\def\unitsbackspace  {\negthinspace}

\unexpanded\def\installunitsseparator#1#2%
  {\setvalue{\??unitseparator#1}{#2}}

\unexpanded\def\phys_units_separator
  {\edef\currentunitsseparator{\unitparameter\c!separator}%
   \csname\??unitseparator
     \ifcsname\??unitseparator\currentunitsseparator\endcsname\currentunitsseparator\else\v!normal\fi
   \endcsname}

\installunitsseparator\v!normal {\cdot}
\installunitsseparator\v!big    {\unitsbigspace}
\installunitsseparator\v!medium {\unitsmediumspace}
\installunitsseparator\v!small  {\unitssmallspace}
\installunitsseparator\v!none   {}

\unexpanded\def\installunitsspace#1#2%
  {\setvalue{\??unitspace#1}{#2}}

\unexpanded\def\phys_units_space
  {\unskip % weird, why is unskip needed
   \edef\currentunitsspace{\unitparameter\c!space}%
   \csname\??unitspace
     \ifcsname\??unitspace\currentunitsspace\endcsname\currentunitsspace\else\v!normal\fi
   \endcsname}

\installunitsspace\v!normal {\unitsmediumspace}
\installunitsspace\v!big    {\unitsbigspace}
\installunitsspace\v!medium {\unitsmediumspace}
\installunitsspace\v!small  {\unitssmallspace}
\installunitsspace\v!none   {}

\newtoks \everyunits % we keep the old \units command so we need a longer one

\appendtoks
    \disablemathpunctuation
\to \everyunits

\appendtoks
    \setuevalue\currentunit{\phys_units_direct{\currentunit}}
\to \everydefineunit

\unexpanded\def\phys_units_direct#1%
  {\begingroup
   \ifdim\lastskip>\zeropoint
     \settrue\c_phys_units_dospace
     \removelastskip
   \fi
   \c_phys_digits_method\unitparameter\c!method\relax
   \ifmmode\else\dontleavehmode\fi
   \edef\currentunit{#1}%
   \edef\unitlanguage{\unitparameter\s!language}%
   \let\prefixlanguage\unitlanguage
   \let\operatorlanguage\unitlanguage
   \the\everyunits
  %\removeunwantedspaces % not ok yet
   \useunitstyleandcolor\c!style\c!color
   \edef\currentunitsalternative{\unitparameter\c!alternative}%
   \ifmmode
     \ifx\currentunitsalternative\v!text
       \expandafter\expandafter\expandafter\phys_units_direct_text_in_math
     \else
       \expandafter\expandafter\expandafter\phys_units_direct_math
     \fi
   \else
     \ifx\currentunitsalternative\v!mathematics
       \expandafter\expandafter\expandafter\phys_units_direct_math_in_text
     \else
       \expandafter\expandafter\expandafter\phys_units_direct_text
     \fi
   \fi}

\unexpanded\def\phys_units_direct_text_in_math#1%
  {\mathtext{%
     \c_phys_units_mode\plustwo
     \phys_units_indeed{#1}%
     \phys_units_finish
   }%
   \endgroup}

\unexpanded\def\phys_units_direct_math#1%
  {\c_phys_units_mode\plusone
   \rm\tf % slow
   \mathtf
   \phys_units_indeed{#1}%
   \phys_units_finish
   \endgroup}

\unexpanded\def\phys_units_direct_text#1%
  {\phys_units_indeed{#1}%
   \phys_units_finish
   \endgroup}

\unexpanded\def\phys_units_direct_math_in_text#1%
  {\removeunwantedspaces % brr
   \startimath
   \c_phys_units_mode\plusthree
   \rm\tf
   \mathtf
   \phys_units_indeed{#1}%
   \phys_units_finish
   \stopimath
   \endgroup}

\unexpanded\def\phys_units_direct_nested#1#2%
  {\phys_units_indeed{#2}}

\appendtoks
    \let\phys_units_direct\phys_units_direct_nested
\to \everyunits

\unexpanded\def\phys_units_indeed#1%
  {\edef\p_order{\unitparameter\c!order}%
   \ifx\p_order\v!reverse\expandafter\clf_unit_reverse\else\expandafter\clf_unit_normal\fi{\detokenize{#1}}}

\unexpanded\def\unitsPUS#1#2#3{\phys_units_next\prefixtext{#1}\unittext{#2}\unitsraise{\suffixtext{#3}}\c_phys_units_state\plusone} % suffix
\unexpanded\def\unitsPU   #1#2{\phys_units_next\prefixtext{#1}\unittext{#2}\c_phys_units_state\plusthree}                           % unit
\unexpanded\def\unitsPS   #1#2{\phys_units_next\prefixtext{#1}\unitsraise{\suffixtext{#2}}\c_phys_units_state\plusone}              % suffix
\unexpanded\def\unitsUS   #1#2{\phys_units_next\unittext{#1}\unitsraise{\suffixtext{#2}}\c_phys_units_state\plusone}                % suffix
\unexpanded\def\unitsP      #1{\phys_units_next\prefixtext{#1}1\c_phys_units_state\plusfour}                                        % prefix
\unexpanded\def\unitsU      #1{\phys_units_next\unittext{#1}\c_phys_units_state\plusthree}                                          % unit
\unexpanded\def\unitsS      #1{\phys_units_start{}\unitsraise{\suffixtext{#1}}\c_phys_units_state\plusone}                          % suffix
\unexpanded\def\unitsO      #1{\phys_units_start\operatortext{#1}\c_phys_units_state\plustwo}                                       % operator
\unexpanded\def\unitsN      #1{\phys_units_start#1\c_phys_units_state\plusfive}                                                     % number
\unexpanded\def\unitsC      #1{\removeunwantedspaces\unittext{#1}\c_phys_units_state\plussix}                                  % connected
\unexpanded\def\unitsQ      #1{\removeunwantedspaces\unitslower{#1}\c_phys_units_state\zerocount}                             %

% Fonts can have a celsius and lack a fahrenheit symbol and as we want
% to be consistent so we check for the counterparts as well. It's slow
% but ok. Of course we could go virtual instead.

\def\phys_units_text_prime      {\textacute}
\def\phys_units_text_doubleprime{\textacute\kern-.25em\textacute}
\def\phys_units_text_celsius    {°C}
\def\phys_units_text_fahrenheit {°F}

\unexpanded\def\checkedtextprime
  {\iffontchar\font"2032\relax\iffontchar\font"2033\relax
     ′\else\phys_units_text_prime\fi\else\phys_units_text_prime
   \fi}

\unexpanded\def\checkedtextdoubleprime
  {\iffontchar\font"2033\relax\iffontchar\font"2032\relax
     ″\else\phys_units_text_doubleprime\fi\else\phys_units_text_doubleprime
   \fi}

% \unexpanded\def\checkedtextcelsius
%   {\ifmmode
%      \phys_units_text_celsius
%    \else\iffontchar\font"2103\relax
%      ℃\else\phys_units_text_celsius
%    \fi\fi}
%
% \unexpanded\def\checkedtextfahrenheit
%   {\ifmmode
%      \phys_units_text_fahrenheit
%    \else\iffontchar\font"2109\relax
%      ℉\else\phys_units_text_fahrenheit
%    \fi\fi}
%
% % but, as users don't like this ...

\let\checkedtextcelsius   \phys_units_text_celsius
\let\checkedtextfahrenheit\phys_units_text_fahrenheit

\setelementnature[unit]    [mixed]
\setelementnature[quantity][mixed]

\let\phys_units_finish\relax

\unexpanded\def\unitsNstart
  {\ifmmode \else
     \settrue\c_phys_units_quantity
     \dostarttagged\t!quantity\empty
     \settrue\c_phys_units_number
     \dostarttagged\t!number\empty
   \fi}

\unexpanded\def\unitsNstop
  {\ifconditional\c_phys_units_number
     \setfalse\c_phys_units_number
     \dostoptagged
   \fi
   \c_phys_units_state\plusfive}

% This is a hack: for some reason \unit{micro meter} like patterns give
% \unitsNstart\unitsNstop so there is a buglet in the parser

\let\unitsNstartindeed\unitsNstart

\unexpanded\def\unitsNstart
  {\doifelsenextchar\unitsNstop\gobbleoneargument\unitsNstartindeed}

% End of hack.

\unexpanded\def\unitsNspace
  {\space}

\unexpanded\def\unitsN#1%
  {\unitsNstart#1\unitsNstop}

\def\phys_units_start
  {\ifmmode
     \dostarttagged\t!mathaction\t!unit
     \bgroup % make an mrow
   \else
     \dostarttagged\t!unit\empty
   \fi
   \let\phys_units_finish\phys_units_stop
   \let\phys_units_start\relax}

\def\phys_units_stop
  {\ifconditional\c_phys_units_number
     \setfalse\c_phys_units_number
     \dostoptagged
   \fi
   \ifconditional\c_phys_units_quantity
     \setfalse\c_phys_units_quantity
     \dostoptagged
   \fi
   \dostoptagged
   \ifmmode
     \egroup
   \fi}

\def\unitsraise
  {\ifcase\c_phys_units_mode
     \expandafter\unitshigh
   \or
     \expandafter\normalsuperscript
   \or
     \expandafter\unitshigh
   \or
     \expandafter\normalsuperscript
   \fi}

\def\unitslower
  {\ifcase\c_phys_units_mode
     \expandafter\unitslow
   \or
     \expandafter\normalsubscript
   \or
     \expandafter\unitslow
   \or
     \expandafter\normalsubscript
   \fi}

\unexpanded\def\phys_units_next
  {\ifcase\c_phys_units_state % start
     \ifconditional\c_phys_units_dospace
      % \ifdim\lastskip=\zeropoint
         \phys_units_space
      % \else
      %   % too tricky ... we could remove and add
      % \fi
     \fi
   \or % 1: suffix
     {\phys_units_separator}%
   \or % 2: operator
   \or % 3: unit
     {\phys_units_separator}%
   \or % 4: prefix
   \or % 5: number
     \phys_units_space
   \or % 6: symbol (connected)
   \fi
   \setfalse\c_phys_units_dospace
   \phys_units_start}

\unexpanded\def\unitsTIMES
  {\ifnum\c_phys_units_state=\plusone % suffix
   \else
     \unitssmallspace
   \fi
   \cdot} % or \times

\unexpanded\def\unitsOUTOF
  {\ifnum\c_phys_units_state=\plusone % suffix
   \else
     \unitssmallspace
   \fi
   :}

\unexpanded\def\unitsSOLIDUS
  {\ifnum\c_phys_units_state=\plusone % suffix
     \unitsbackspace
   \fi
   {/}%
   }%\unitsbackspace}

\definelabelclass [unit]     [2]
\definelabelclass [operator] [2]
\definelabelclass [prefix]   [2]
\definelabelclass [suffix]   [2] % This is only a label because we want to show them in a table.

\clf_definelabels{prefix}{prefixes}\s!false\relax
\clf_definelabels{unit}{units}\s!false\relax
\clf_definelabels{operator}{operators}\s!false\relax
\clf_definelabels{suffix}{suffixes}\s!false\relax

%D You can define additional units:
%D
%D \starttyping
%D \registerunit
%D   [unit]
%D   [point=point,
%D    basepoint=basepoint,
%D    scaledpoint=scaledpoint,
%D    didot=didot,
%D    cicero=cicero]
%D \stoptyping
%D
%D Possible categories are: \type {prefix}, \type {unit}, \type {operator},
%D \type {suffix}, \type {symbol},\type {packaged}. You also need to define
%D labels:
%D
%D \starttyping
%D \setupunittext
%D   [point=pt,
%D    basepoint=bp,
%D    scaledpoint=sp,
%D    didot=dd,
%D    cicero=cc]
%D \stoptyping

\unexpanded\def\registerunit
  {\dodoubleempty\phys_units_register}

\def\phys_units_register[#1][#2]%
  {\clf_registerunit{#1}{#2}}

%D You can generate a list as follows:
%D
%D \starttyping
%D \usemodule[phy-01]
%D
%D \ShowUnitsTable % [prefixes]
%D \stoptyping

%D Now we define the standard units command:

\defineunit
  [unit]

%D Example:
%D
%D \startbuffer[definitions]
%D \startluacode
%D     languages.data.labels.prefixes.whatever = {
%D         Kilo = "olik"
%D     }
%D
%D     languages.data.labels.units.whatever = {
%D         Meter  = "retem",
%D         Second = "dnoces",
%D     }
%D
%D     languages.data.labels.operators.whatever = {
%D         Solidus = " rep "
%D     }
%D \stopluacode
%D \stopbuffer
%D
%D \startbuffer[sample]
%D \startlines
%D \lunit{10 km/s}
%D \lunit{10 Kilo Meter/s}
%D \lunit{10 kilo Meter/s}
%D \lunit{10 Kilo m/s}
%D \lunit{10 k Meter/s}
%D \stoplines
%D \stopbuffer
%D
%D \typebuffer[definitions] \getbuffer[definitions]
%D
%D \startbuffer
%D \typebuffer[sample]
%D
%D \defineunits[lunit]                 \getbuffer[sample]
%D \defineunits[lunit][label=test]     \getbuffer[sample]
%D \defineunits[lunit][label=whatever] \getbuffer[sample]
%D \stopbuffer
%D
%D \typebuffer \getbuffer
%D
%D Another example:
%D
%D \starttyping
%D \startluacode
%D     languages.data.labels.units.foo = {
%D         Liter = "l"
%D     }
%D     languages.data.labels.units.bar = {
%D         Liter = "L"
%D     }
%D \stopluacode
%D
%D \defineunits[lunit]            \lunit{10 l/s}\par
%D \defineunits[funit][label=foo] \funit{10 l/s}\par
%D \defineunits[bunit][label=bar] \bunit{10 l/s}\par
%D \stoptyping

\protect \endinput