path: root/doc/context/sources/general/manuals/cld/cld-somemoreexamples.tex

% language=uk

\startcomponent cld-somemoreexamples

\environment cld-environment

\usemodule[morse]

\startchapter[title=Some more examples]

\startsection[title=Appetizer]

Before we give some more examples, we will have a look at the way the title page
is made. This way you get an idea what more is coming.

\typefile {cld-mkiv-simple-titlepage.cld}

This does not look that bad, does it? Of course in pure \TEX\ code it looks
mostly the same but loops and calculations feel a bit more natural in \LUA\ then
in \TEX. The result is shown in \in {figure} [fig:cover]. The actual cover page
was derived from this.

\startplacefigure[location=here,reference=fig:cover,title={The simplified cover page.}]
    \doiffileexistselse {cld-mkiv-simple-titlepage.pdf} {
        \externalfigure
            [cld-mkiv-simple-titlepage.pdf]
            [height=.5\textheight]
    } {
        \scale
            [height=.5\textheight]
            {\cldprocessfile{cld-mkiv-simple-titlepage.cld}}
    }
\stopplacefigure

\stopsection

\startsection[title=A few examples]

As it makes most sense to use the \LUA\ interface for generated text, here is
another example with a loop:

\startbuffer
context.startitemize { "a", "packed", "two" }
  for i=1,10 do
    context.startitem()
      context("this is item %i",i)
    context.stopitem()
  end
context.stopitemize()
\stopbuffer

\typebuffer

\ctxluabuffer

Just as you can mix \TEX\ with \XML\ and \METAPOST, you can define bits and
pieces of a document in \LUA. Tables are good candidates:

\startbuffer
local one = {
  align = "middle",
  style = "type",
}
local two = {
  align = "middle",
  style = "type",
  background = "color",
  backgroundcolor = "darkblue",
  foregroundcolor = "white",
}
local random = math.random
context.bTABLE { framecolor = "darkblue" }
    for i=1,10 do
      context.bTR()
      for i=1,20 do
          local r = random(99)
          context.bTD(r < 50 and one or two)
          context("%2i",r)
          context.eTD()
      end
      context.eTR()
    end
context.eTABLE()
\stopbuffer

\typebuffer

\placetable[top][tab:random]{A table generated by \LUA.}{\ctxluabuffer}

Here we see a function call to \type {context} in the most indented line. The
first argument is a format that makes sure that we get two digits and the random
number is substituted into this format. The result is shown in
\in{table}[tab:random]. The line correction is ignored when we use this table as
a float, otherwise it assures proper vertical spacing around the table. Watch how
we define the tables \type {one} and \type {two} beforehand. This saves 198
redundant table constructions.

Not all code will look as simple as this. Consider the following:

\starttyping
context.placefigure(
  "caption",
  function() context.externalfigure( { "cow.pdf" } ) end
)
\stoptyping

Here we pass an argument wrapped in a function. If we would not do that, the
external figure would end up wrong, as arguments to functions are evaluated
before the function that gets them (we already showed some alternative approaches
in previous chapters). A function argument is treated as special and in this case
the external figure ends up right. Here is another example:

\startbuffer
context.placefigure("Two cows!",function()
  context.bTABLE()
    context.bTR()
      context.bTD()
        context.externalfigure(
            { "cow.pdf" },
            { width = "3cm", height = "3cm" }
        )
      context.eTD()
      context.bTD { align = "{lohi,middle}" }
        context("and")
      context.eTD()
      context.bTD()
        context.externalfigure(
            { "cow.pdf" },
            { width = "4cm", height = "3cm" }
        )
      context.eTD()
    context.eTR()
  context.eTABLE()
end)
\stopbuffer

\typebuffer

In this case the figure is not an argument so it gets flushed sequentially
with the rest.

\ctxluabuffer

\stopsection

\startsection[title=Styles]

Say that you want to typeset a word in a bold font. You can do
that this way:

\starttyping
context("This is ")
context.bold("important")
context("!")
\stoptyping

Now imagine that you want this important word to be in red too. As we have
a nested command, we end up with a nested call:

\starttyping
context("This is ")
context.bold(function() context.color( { "red" }, "important") end)
context("!")
\stoptyping

or

\starttyping
context("This is ")
context.bold(context.delayed.color( { "red" }, "important"))
context("!")
\stoptyping

In that case it's good to know that there is a command that combines both
features:

\starttyping
context("This is ")
context.style( { style = "bold", color = "red" }, "important")
context("!")
\stoptyping

But that is still not convenient when we have to do that often. So, you can wrap
the style switch in a function.

\starttyping
local function mycommands.important(str)
    context.style( { style = "bold", color = "red" }, str )
end

context("This is ")
mycommands.important( "important")
context(", and ")
mycommands.important( "this")
context(" too !")
\stoptyping

Or you can setup a named style:

\starttyping
context.setupstyle( { "important" }, { style = "bold", color = "red" } )

context("This is ")
context.style( { "important" }, "important")
context(", and ")
context.style( { "important" }, "this")
context(" too !")
\stoptyping

Or even define one:

\starttyping
context.definestyle( { "important" }, { style = "bold", color = "red" } )

context("This is ")
context.important("important")
context(", and ")
context.important("this")
context(" too !")
\stoptyping

This last solution is especially handy for more complex cases:

\startbuffer
context.definestyle( { "important" }, { style = "bold", color = "red" } )

context("This is ")
context.startimportant()
context.inframed("important")
context.stopimportant()
context(", and ")
context.important("this")
context(" too !")
\stopbuffer

\typebuffer

\ctxluabuffer

\stopsection

\startsection[title=A complete example]

One day my 6 year old niece Lorien was at the office and wanted to know what I
was doing. As I knew she was practicing arithmetic at school I wrote a quick and
dirty script to generate sheets with exercises. The most impressive part was that
the answers were included. It was a rather braindead bit of \LUA, written in a
few minutes, but the weeks after I ended up running it a few more times, for her
and her friends, every time a bit more difficult and also using different
arithmetic. It was that script that made me decide to extend the basic cld manual
into this more extensive document.

We generate three columns of exercises. Each exercise is a row in a table. The
last argument to the function determines if answers are shown.

\starttyping
local random = math.random

local function ForLorien(n,maxa,maxb,answers)
  context.startcolumns { n = 3 }
  context.starttabulate { "|r|c|r|c|r|" }
  for i=1,n do
    local sign = random(0,1) > 0.5
    local a, b = random(1,maxa or 99), random(1,max or maxb or 99)
    if b > a and not sign then a, b = b, a end
    context.NC()
    context(a)
    context.NC()
    context.mathematics(sign and "+" or "-")
    context.NC()
    context(b)
    context.NC()
    context("=")
    context.NC()
    context(answers and (sign and a+b or a-b))
    context.NC()
    context.NR()
  end
  context.stoptabulate()
  context.stopcolumns()
  context.page()
end
\stoptyping

This is a typical example of where it's more convenient to write the code in
\LUA\ that in \TEX's macro language. As a consequence setting up the page also
happens in \LUA:

\starttyping
context.setupbodyfont {
  "palatino",
  "14pt"
}

context.setuplayout {
  backspace = "2cm",
  topspace  = "2cm",
  header    = "1cm",
  footer    = "0cm",
  height    = "middle",
  width     = "middle",
}
\stoptyping

This leave us to generate the document. There is a pitfall here: we need to use
the same random number for the exercises and the answers, so we freeze and
defrost it. Functions in the \type {commands} namespace implement functionality
that is used at the \TEX\ end but better can be done in \LUA\ than in \TEX\ macro
code. Of course these functions can also be used at the \LUA\ end.

\starttyping
context.starttext()

  local n = 120

  commands.freezerandomseed()

  ForLorien(n,10,10)
  ForLorien(n,20,20)
  ForLorien(n,30,30)
  ForLorien(n,40,40)
  ForLorien(n,50,50)

  commands.defrostrandomseed()

  ForLorien(n,10,10,true)
  ForLorien(n,20,20,true)
  ForLorien(n,30,30,true)
  ForLorien(n,40,40,true)
  ForLorien(n,50,50,true)

context.stoptext()
\stoptyping

\placefigure
  [here]
  [fig:lorien]
  {Lorien's challenge.}
  {\startcombination
     {\externalfigure[cld-005.pdf][page=1,width=.45\textwidth,frame=on]} {exercises}
     {\externalfigure[cld-005.pdf][page=6,width=.45\textwidth,frame=on]} {answers}
   \stopcombination}

A few pages of the result are shown in \in {figure} [fig:lorien]. In the
\CONTEXT\ distribution a more advanced version can be found in \type
{s-edu-01.cld} as I was also asked to generate multiplication and table
exercises. In the process I had to make sure that there were no duplicates on a
page as she complained that was not good. There a set of sheets is generated
with:

\starttyping
moduledata.educational.arithematic.generate {
  name     = "Bram Otten",
  fontsize = "12pt",
  columns  = 2,
  run      = {
    { method = "bin_add_and_subtract", maxa =   8, maxb =   8 },
    { method = "bin_add_and_subtract", maxa =  16, maxb =  16 },
    { method = "bin_add_and_subtract", maxa =  32, maxb =  32 },
    { method = "bin_add_and_subtract", maxa =  64, maxb =  64 },
    { method = "bin_add_and_subtract", maxa = 128, maxb = 128 },
  },
}
\stoptyping

\stopsection

\startsection[title=Interfacing]

The fact that we can define functionality using \LUA\ code does not mean that we
should abandon the \TEX\ interface. As an example of this we use a relatively
simple module for typesetting morse code.\footnote {The real module is a bit
larger and can format verbose morse.} First we create a proper namespace:

\starttyping

moduledata.morse = moduledata.morse or { }
local morse      = moduledata.morse
\stoptyping

We will use a few helpers and create shortcuts for them. The first helper loops
over each \UTF\ character in a string. The other two helpers map a character onto
an uppercase (because morse only deals with uppercase) or onto an similar shaped
character (because morse only has a limited character set).

\starttyping
local utfcharacters = string.utfcharacters
local ucchars, shchars = characters.ucchars, characters.shchars
\stoptyping

The morse codes are stored in a table.

\starttyping
local codes = {

    ["A"] = "·—",     ["B"] = "—···",
    ["C"] = "—·—·",   ["D"] = "—··",
    ["E"] = "·",      ["F"] = "··—·",
    ["G"] = "——·",    ["H"] = "····",
    ["I"] = "··",     ["J"] = "·———",
    ["K"] = "—·—",    ["L"] = "·—··",
    ["M"] = "——",     ["N"] = "—·",
    ["O"] = "———",    ["P"] = "·——·",
    ["Q"] = "——·—",   ["R"] = "·—·",
    ["S"] = "···",    ["T"] = "—",
    ["U"] = "··—",    ["V"] = "···—",
    ["W"] = "·——",    ["X"] = "—··—",
    ["Y"] = "—·——",   ["Z"] = "——··",

    ["0"] = "—————",  ["1"] = "·————",
    ["2"] = "··———",  ["3"] = "···——",
    ["4"] = "····—",  ["5"] = "·····",
    ["6"] = "—····",  ["7"] = "——···",
    ["8"] = "———··",  ["9"] = "————·",

    ["."] = "·—·—·—", [","] = "——··——",
    [":"] = "———···", [";"] = "—·—·—",
    ["?"] = "··——··", ["!"] = "—·—·——",
    ["-"] = "—····—", ["/"] = "—··—· ",
    ["("] = "—·——·",  [")"] = "—·——·—",
    ["="] = "—···—",  ["@"] = "·——·—·",
    ["'"] = "·————·", ['"'] = "·—··—·",

    ["À"] = "·——·—",
    ["Å"] = "·——·—",
    ["Ä"] = "·—·—",
    ["Æ"] = "·—·—",
    ["Ç"] = "—·—··",
    ["É"] = "··—··",
    ["È"] = "·—··—",
    ["Ñ"] = "——·——",
    ["Ö"] = "———·",
    ["Ø"] = "———·",
    ["Ü"] = "··——",
    ["ß"] = "··· ···",

}

morse.codes = codes
\stoptyping

As you can see, there are a few non \ASCII\ characters supported as well. There
will never be full \UNICODE\ support simply because morse is sort of obsolete.
Also, in order to support \UNICODE\ one could as well use the bits of \UTF\
characters, although \unknown\ memorizing the whole \UNICODE\ table is not much
fun.

We associate a metatable index function with this mapping. That way we can not
only conveniently deal with the casing, but also provide a fallback based on the
shape. Once found, we store the representation so that only one lookup is needed
per character.

\starttyping
local function resolvemorse(t,k)
    if k then
        local u = ucchars[k]
        local v = rawget(t,u) or rawget(t,shchars[u]) or false
        t[k] = v
        return v
    else
        return false
    end
end

setmetatable(codes, { __index = resolvemorse })
\stoptyping

Next comes some rendering code. As we can best do rendering at the \TEX\ end we
just use macros.

\starttyping
local MorseBetweenWords      = context.MorseBetweenWords
local MorseBetweenCharacters = context.MorseBetweenCharacters
local MorseLong              = context.MorseLong
local MorseShort             = context.MorseShort
local MorseSpace             = context.MorseSpace
local MorseUnknown           = context.MorseUnknown
\stoptyping

The main function is not that complex. We need to keep track of spaces and
newlines. We have a nested loop because a fallback to shape can result in
multiple characters.

\starttyping
function morse.tomorse(str)
    local inmorse = false
    for s in utfcharacters(str) do
        local m = codes[s]
        if m then
            if inmorse then
                MorseBetweenWords()
            else
                inmorse = true
            end
            local done = false
            for m in utfcharacters(m) do
                if done then
                    MorseBetweenCharacters()
                else
                    done = true
                end
                if m == "·" then
                    MorseShort()
                elseif m == "—" then
                    MorseLong()
                elseif m == " " then
                    MorseBetweenCharacters()
                end
            end
            inmorse = true
        elseif s == "\n" or s == " " then
            MorseSpace()
            inmorse = false
        else
            if inmorse then
                MorseBetweenWords()
            else
                inmorse = true
            end
            MorseUnknown(s)
        end
    end
end
\stoptyping

We use this function in two additional functions. One typesets a file, the other
a table of available codes.

\starttyping
function morse.filetomorse(name,verbose)
    morse.tomorse(resolvers.loadtexfile(name),verbose)
end

function morse.showtable()
    context.starttabulate { "|l|l|" }
    for k, v in table.sortedpairs(codes) do
        context.NC() context(k)
        context.NC() morse.tomorse(v,true)
        context.NC() context.NR()
    end
    context.stoptabulate()
end
\stoptyping

We're done with the \LUA\ code that we can either put in an external file or put
in the module file. The \TEX\ file has two parts. The typesetting macros that we
use at the \LUA\ end are defined first. These can be overloaded.

\starttyping
\def\MorseShort
  {\dontleavehmode
   \vrule
      width  \MorseWidth
      height \MorseHeight
      depth  \zeropoint
   \relax}

\def\MorseLong
  {\dontleavehmode
   \vrule
      width 3\dimexpr\MorseWidth
      height         \MorseHeight
      depth          \zeropoint
   \relax}

\def\MorseBetweenCharacters
  {\kern\MorseWidth}

\def\MorseBetweenWords
  {\hskip3\dimexpr\MorseWidth\relax}

\def\MorseSpace
  {\hskip7\dimexpr\MorseWidth\relax}

\def\MorseUnknown#1
  {[\detokenize{#1}]}
\stoptyping

The dimensions are stored in macros as well. Of course we could provide a proper
setup command, but it hardly makes sense.

\starttyping
\def\MorseWidth {0.4em}
\def\MorseHeight{0.2em}
\stoptyping

Finally we have arrived at the macros that interface to the \LUA\ functions.

\starttyping
\def\MorseString#1{\ctxlua{moduledata.morse.tomorse(\!!bs#1\!!es)}}
\def\MorseFile  #1{\ctxlua{moduledata.morse.filetomorse("#1")}}
\def\MorseTable   {\ctxlua{moduledata.morse.showtable()}}
\stoptyping

\startbuffer
\Morse{A more advanced solution would be to convert a node list. That
way we can deal with weird input.}
\stopbuffer

A string is converted to morse with the first command.

\typebuffer

This shows up as:

\startalignment[flushleft,tolerant]\getbuffer\stopalignment

Reduction and uppercasing is demonstrated in the next example:

\startbuffer
\MorseString{ÀÁÂÃÄÅàáâãäå}
\stopbuffer

\typebuffer

This gives:

\startalignment[flushleft,tolerant]\getbuffer\stopalignment

\stopsection

\startsection[title=Using helpers]

The next example shows a bit of \LPEG. On top of the standard functionality
a few additional functions are provided. Let's start with a pure \TEX\
example:

\startbuffer
\defineframed
  [colored]
  [foregroundcolor=red,
   foregroundstyle=\underbar,
   offset=.1ex,
   location=low]
\stopbuffer

\typebuffer \getbuffer

\startbuffer
\processisolatedwords {\input ward \relax} \colored
\stopbuffer

\typebuffer \blank \getbuffer \blank

Because this processor macro operates at the \TEX\ end it has some limitations.
The content is collected in a very narrow box and from that a regular paragraph
is constructed. It is for this reason that no color is applied: the snippets that
end up in the box are already typeset.

An alternative is to delegate the task to \LUA:

\startbuffer
\startluacode
local function process(data)

  local words = lpeg.split(lpeg.patterns.spacer,data or "")

  for i=1,#words do
    if i == 1 then
        context.dontleavehmode()
    else
        context.space()
    end
    context.colored(words[i])
  end

end

process(io.loaddata(resolvers.findfile("ward.tex")))
\stopluacode
\stopbuffer

\typebuffer \blank \getbuffer \blank

The function splits the loaded data into a table with individual words. We use a
splitter that splits on spacing tokens. The special case for \type {i = 1} makes
sure that we end up in horizontal mode (read: properly start a paragraph). This
time we do get color because the typesetting is done directly. Here is an
alternative implementation:

\starttyping
local done = false

local function reset()
    done = false
    return true
end

local function apply(s)
  if done then
    context.space()
  else
    done = true
    context.dontleavehmode()
  end
  context.colored(s)
end

local splitter = lpeg.P(reset)
               * lpeg.splitter(lpeg.patterns.spacer,apply)

local function process(data)
  lpeg.match(splitter,data)
end
\stoptyping

This version is more efficient as it does not create an intermediate table. The
next one is comaprable:

\starttyping
local function apply(s)
  context.colored("%s ",s)
end

local splitter lpeg.splitter(lpeg.patterns.spacer,apply)

local function process(data)
  context.dontleavevmode()
  lpeg.match(splitter,data)
  context.removeunwantedspaces()
end
\stoptyping

\stopsection

\startsection[title=Formatters]

Sometimes can save a bit of work by using formatters. By default, the \type {context}
command, when called directly, applies a given formatter. But when called as table
this feature is lost because then we want to process non|-|strings as well. The next
example shows a way out:

\startbuffer
context("the current emwidth is %p",\number\emwidth)
context.par()
context.formatted("the current emwidth is %p",\number\emwidth)
context.par()
context.bold(string.formatters["the current emwidth is %p"](\number\emwidth))
context.par()
context.formatted.bold("the current emwidth is %p",\number\emwidth)
\stopbuffer

The last one is the most interesting one here: in the subnamespace \type
{formatted} (watch the \type {d}) a format specification with extra arguments is
expected.

\ctxluabuffer

\stopsection

\stopchapter

\stopcomponent