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%D \module
%D [ file=lang-frq,
%D version=2004.01.15,
%D title=\CONTEXT\ Language Macros,
%D subtitle=Frequency Tables,
%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.
\endinput
\writestatus{loading}{ConTeXt Language Macros / Frequency Tables}
%D Some day I might redo this \LUA. But anyway, who uses it. It's rather old code.
\unprotect
%M \usemodule[layout]
%D \macros
%D {charwidthmethod}
%D
%D This module implements a method for determining the width of an
%D average character in a language. It uses the dimensions of the
%D current fonts.
%D
%D \def\ShwChrWd#1#2#3%
%D {\chardef\charwidthmethod#1\relax
%D \mainlanguage[#2#3]\the\dimexpr(\averagecharwidth)}
%D
%D \starttabulate[|c|c|c|c|c|c|]
%D \HL
%D \NC \NC\bf0=amount\NC\bf1=.5em\NC2=ex\NC\bf3=frequency\NC\bf4=list\NC\NR
%D \HL
%D \NC\bf en\NC\ShwChrWd0en\NC\ShwChrWd1en\NC\ShwChrWd2en\NC\ShwChrWd3en\NC\ShwChrWd4en\NC\NR
%D \NC\bf nl\NC\ShwChrWd0nl\NC\ShwChrWd1nl\NC\ShwChrWd2nl\NC\ShwChrWd3nl\NC\ShwChrWd4nl\NC\NR
%D \NC\bf de\NC\ShwChrWd0de\NC\ShwChrWd1de\NC\ShwChrWd2de\NC\ShwChrWd3de\NC\ShwChrWd4de\NC\NR
%D \HL
%D \stoptabulate
%D
%D Method~1 ignores the widths and assumes that each character has a
%D width of .5em, which is true for most monospaced fonts. Method~2
%D takes the x as starting point, and assumes that it's height kind of
%D matches its width. Method~3 is the best one, and determines the
%D average width based on the language specific character table.
%D Method~4 is a mixture between the first two methods: character
%D specific widths applied to an equal distribution. Method~0 reports
%D the total count, which normally is~100.
\setnewconstant\charwidthmethod=3 % 0=amount 1=em 2=ex 3=frequency 4=flattened >4=ex
%D \macros
%D {charwidthlanguage}
%D
%D The language used for the calculations is defined as:
\def\charwidthlanguage{\currentmainlanguage}
%D \macros
%D {charfreq}
%D
%D This method comes into action in the following macro:
\def\charfreq#1 #2 % character fraction
{+(\ifcase\charwidthmethod
#2\dimexpr100\onepoint\relax
\or
#2\dimexpr\emwidth/2\relax
\or
#2\dimexpr\exheight\relax
\or
#2\fontcharwd\font`#1%
\or
\dimexpr100\fontcharwd\font`#1/\charactertsize\charwidthlanguage\relax % ugly hack
\else
#2\dimexpr\exheight\relax
\fi)}
%D \macros
%D {startcharactertable}
%D
%D A frequency table is defined with the following macro. The \type
%D {charfreq} macro is used in this table.
\installcorenamespace{frequencywidths}
\installcorenamespace{frequencycounts}
\aliased\let\stopcharactertable\relax
\permanent\protected\def\startcharactertable[#1]#2\stopcharactertable % \dimexpr has fuzzy lookahead
{\startnointerference
\gdefcsname\??frequencywidths#1\endcsname{#2}% the width vector
\scratchcounter\zerocount \def\charfreq##1 ##2 {\advance\scratchcounter\plusone} #2%
\xdefcsname\??frequencycounts#1\endcsname{\the\scratchcounter}% the character count
\stopnointerference}
%D \macros
%D {charactertable,charactertsize}
%D
%D The table content as well as the number of entries can be fetched with
%D the following two macros. The architecture of the table and calling
%D macro permits a fully expandable application.
\permanent\def\charactertable#1%
{\csname\??frequencywidths\ifcsname\??frequencywidths#1\endcsname#1\else\s!en\fi\endcsname}
\permanent\def\charactertsize#1%
{\csname\??frequencycounts\ifcsname\??frequencycounts#1\endcsname#1\else\s!en\fi\endcsname}
%D Although it is of hardly any use, you can inherit a character table:
%D
%D \starttyping
%D \startcharactertable[cz] \charactertable{en} \stopcharactertable
%D \stoptyping
\startcharactertable[en]
% empty
\stopcharactertable % kind of default
%D \macros
%D {averagecharwidth}
%D
%D This macro reports the average width for the current main
%D language (\the \dimexpr (\averagecharwidth)).
\permanent\def\averagecharwidth{\dimexpr(\zeropoint\charactertable\charwidthlanguage)/100\relax}
\permanent\protected\def\showcharfreq
{\hbox\bgroup
\charwidthlanguage:%
\dostepwiserecurse\zerocount\plusfour\plusone
{\setconstant\charwidthmethod\recurselevel\relax
\enspace\recurselevel/\the\dimexpr(\averagecharwidth)}%
\egroup}
%D Just for fun, we show a few frequency tables as graphic (\in {figure}
%D [fig:charfreq]).
%D
%D \startbuffer
%D \definepalet [charfreq] [en=darkred, nl=darkgreen, de=darkblue]
%D
%D \def\charfreq#1 #2 %
%D {\startMPdrawing
%D interim linejoin := butt ;
%D a := ASCII "#1" ;
%D if (a >= (ASCII "a")) and (a <= (ASCII "z")) :
%D draw ((0,#2*.25cm)--origin--(0,#2*.5cm))
%D shifted (a*4mm+o,0)
%D withpen pencircle scaled .5mm
%D withcolor c;
%D fi ;
%D \stopMPdrawing}
%D
%D \resetMPdrawing
%D \startMPdrawing
%D numeric a, o ; a := o := 0 ;
%D color c ; c := .5white ;
%D string s ; s := "" ;
%D \stopMPdrawing
%D
%D \startMPdrawing o := 0mm ; c := \MPcolor{charfreq:en} ; \stopMPdrawing
%D \charactertable{en}
%D
%D \startMPdrawing o := 1mm ; c := \MPcolor{charfreq:nl} ; \stopMPdrawing
%D \charactertable{nl}
%D
%D \startMPdrawing o := 2mm ; c := \MPcolor{charfreq:de} ; \stopMPdrawing
%D \charactertable{de}
%D
%D \startMPdrawing
%D for a := ASCII "a" upto ASCII "z" :
%D draw textext.bot("\strut\tttf " & char a) shifted (a*4mm+1mm,-1mm) ;
%D endfor ;
%D \stopMPdrawing
%D
%D \MPdrawingdonetrue \getMPdrawing \resetMPdrawing
%D \stopbuffer
%D
%D \placefigure
%D [here]
%D [fig:charfreq]
%D {The character distributions for English, Dutch and German.}
%D {\getbuffer}
%D
%D A few samples of usage of this mechanism are shown below:
%D
%D \startbuffer
%D {\mainlanguage[en]\hsize65\averagecharwidth\mainlanguage[en]\input ward \blank}
%D {\mainlanguage[nl]\hsize65\averagecharwidth\mainlanguage[en]\input ward \blank}
%D {\mainlanguage[de]\hsize65\averagecharwidth\mainlanguage[en]\input ward \blank}
%D \stopbuffer
%D
%D \typebuffer \getbuffer
%D
%D Although the widthts differ, the consequenes for breaking the paragraph
%D into lines are minimal.
%D \macros
%D {freezeaveragecharacterwidth}
%D
%D This macro can be used to make sure that the width does not change during a
%D page break when another font is used.
\aliased\let\normalaveragecharacterwidth\averagecharacterwidth
\permanent\def\freezeaveragecharacterwidth % global
{\enforced\xdef\averagecharacterwidth{\dimexpr\the\normalaveragecharacterwidth\relax}}
%D Example:
%D
%D \starttyping
%D \input lang-frq.mkiv
%D \input lang-frd.mkiv
%D
%D \setupbodyfont
%D [dejavu]
%D
%D \setemeasure{textwidth}{\the\dimexpr70\averagecharwidth}
%D
%D \setuplayout
%D [width=\measure{textwidth}]
%D
%D \showframe
%D
%D \starttext
%D \input ward
%D \stoptext
%D \stoptyping
\protect \endinput
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