[Tex/LaTex] Parsing hexadecimal numbers to binary and iterating over bits

package-writingparsingtikz-pgf

I'm currently working on a software for an graphic display, so I recreated it in TikZ for documentation purposes:

image of the display

I currently use this to set individual pixels on the display:

\setpixel{x}{y}

Where x and y are coordinates between 0 and 132/64.

The real display is separated into 8 pages, each 8 pixels high, and a byte sent to the display is displayed as a column. See this image for details.

Since I don't want to always calculate the individual pixels, I'd like the LaTeX variant to behave like the real display, that is, I want some command like

\dispbyte{0x01}
\dispbyte{0x03}
\dispbyte{0x07}
\dispbyte{0x0F}
\dispbyte{0x1F}
\dispbyte{0x3F}
\dispbyte{0x7F}
\dispbyte{0xFF}

(this would create one of the triangles above)
I have an idea how I'd implement counting of the current column and page switching and all that — shouldn't be hard with some counters after all — but I just can't find out how to parse the hexadecimal values and then iterate over every bit inside them.

I've found fmtcount and binhex.tex, but they only display a LaTeX counter in another format, and I can't understand their code at all.

The finished source code (display.sty) and some examples are now available at http://cmpl.cc/downloads/disp/

Best Answer

The following is less impressive than the other answers from the visual point of view (Mark, I like yours!), but addresses the actual question of the OP: Bit-wise iteration over hexadecimal values, which becomes fairly easy when using the bitset package by Heiko Oberdiek:

\documentclass{article}
\usepackage{bitset}
\usepackage{pgf,pgffor}

\begin{document}

  \bitsetSetHex{mybitset}{AA}
  % use \bitsetGetSetBitList
  % expand first
  \edef\mybits{\bitsetGetSetBitList{mybitset}}
  \noindent
  \foreach \bit in \mybits {%
    Bit \bit{} is set! \\ 
  }

  % just itereate all bits
  \noindent
  \foreach \i in {0,...,7} {%
    Bit \i: \bitsetGet{mybitset}{\i} \\
  }

\end{document}

enter image description here

Related Solutions

[Tex/LaTex] Is it possible to clear tikz/pgf options

This seems to work. Is it preferable?

\begin{tikzpicture}[every path/.style={fill=red}]
{
  \tikzset{every path/.style={}}
  \clip (0,0) -- (1,0) -- (1,1) -- (0,0);
}
\draw (0,0) rectangle (1,1);
\end{tikzpicture}

Edited 2012-12-27 by Andrew Stacey An issue with the above is how clip interacts with setting the bounding box. When a clip is in force, the clipping path should set the bounding box and all clipped paths should not be taken into account when computing the bounding box. Unfortunately, while a clip lasts until the end of a scope, the method by which subsequent paths are ignored (for bounding box computations) only lasts to the end of the current group. I (Andrew Stacey) would actually class this as a TikZ bug: since the clip lasts to the end of the scope the restriction on the bounding box computation should equally last to the end of the scope. There are various ways to fix this:

Since it is usual to restrict a clip to within a scope, put every path/.append style={overlay} on the relevant scope:

\begin{tikzpicture}[every path/.style={fill=red}]
\begin{scope}[every path/.append style={overlay}]
{
  \tikzset{every path/.style={}}
  \clip (0,0) -- (1,0) -- (1,1) -- (0,0);
}
\draw (-1,-1) rectangle (2,2);
\end{scope}
\end{tikzpicture}

The overlay is removed from the clip path as its options are cleared, but it is retained on all other paths in the scope.

For a little more intuitive control, the overlay key can be augmented to take true or false (though due to implementation the value of true/false needs inverting). Then:

\documentclass{article}
\usepackage{tikz}

\def\invertTFtrue{false}
\def\invertTFfalse{true}
\tikzoption{overlay}[true]{\csname pgf@relevantforpicturesize\csname
invertTF#1\endcsname\endcsname}

\begin{document}

\fbox{%
\begin{tikzpicture}[every path/.style={fill=red}]
\begin{scope}[overlay]
{
  \tikzset{every path/.style={}}
  \clip[overlay=false] (0,0) -- (1,0) -- (1,1) -- (0,0);
}
  \draw (-1,-1) rectangle (2,2);
\end{scope}
\end{tikzpicture}}
\end{document}

Lastly, the overlay/clip mechanism can be fixed so that it works with scopes rather than groups. To do this properly and elegantly would require fixing the underlying code a little, the following uses the available hooks to achieve the same end.

\documentclass{article}
\usepackage{tikz}

\makeatletter

\def\invertTFtrue{false}
\def\invertTFfalse{true}

\tikzset{
  fix clips to scope/.style={%
    every scope/.append style={%
      execute at end scope={%
        \expandafter\global\csname               pgf@relevantforpicturesize\savescopeoverlay\endcsname
      },
      execute at begin scope={%
        \edef\savescopeoverlay{\ifpgf@relevantforpicturesize true\else                   false\fi}%
      }
    },
    globalise overlays,
    clip/.append code={\aftergroup\globaloverlay}
  },
  globalise overlays/.code={%
    \tikzoption{overlay}[true]{\expandafter\global\csname       pgf@relevantforpicturesize\csname invertTF#1\endcsname\endcsname}
  }
}

\def\globaloverlay{\global\pgf@relevantforpicturesizefalse}
\makeatletter

\begin{document}

\fbox{%
\begin{tikzpicture}[fix clips to scope,every path/.style={fill=red}]
\begin{scope}
{
  \tikzset{every path/.style={}}
  \clip (0,0) -- (1,0) -- (1,1) -- (0,0);
}
  \draw (-1,-1) rectangle (2,2);
\end{scope}
\draw (-1,1) rectangle (2,2);
\end{tikzpicture}}
\end{document}

[Tex/LaTex] Parse a string into tokens of numbers and not numbers

With the experimental (but pretty much ready for release) package l3regex (found in the l3experimental bundle on CTAN), this task is a piece of cake.

\documentclass{article}
\usepackage{l3regex,xparse}
\ExplSyntaxOn
\seq_new:N \l_uiy_result_seq
\NewDocumentCommand { \UiySplit } { m }
  {
    \regex_extract_all:nnN { \D+ | \d+(?:\.\d*)? } {#1} \l_uiy_result_seq
    \seq_map_inline:Nn \l_uiy_result_seq { item:~##1\par }
  }
\ExplSyntaxOff
\begin{document}
  \UiySplit{ljksadflh23898129hfafh0324.22234}
\end{document}

The \regex line splits the user input #1 into pieces which either consist of one or more (+) non-digits (\D), or (|) of one or more digits (\d), followed maybe (? acting on the group (...), which we want to be "non-capturing", done using (?:...)) by a dot (\. escaped dot, because the dot has a special meaning) and zero or more digits (\d*). The line below maps through all the matches we found, with ##1 being a single match. Of course, you can do whatever you want to do with the items of the sequence \l_uiy_result_seq.

Edit: The module also provides regular expression replacements. If I remember the syntax correctly, the following should work.

\ExplSyntaxOn
\seq_new:N \l_uiy_result_seq
\NewDocumentCommand { \UiySplit } { m }
  {
    \tl_set:Nn \l_uiy_result_tl {#1}
    \regex_replace_all:nnN
        { (\D+) (\d+(\.\d*)) }
        { \c{uiy_do:nn} \cB{\1\cE} \cB{\2\cE} }
        \l_uiy_result_tl
    \tl_use:N \l_uiy_result_tl
  }
\cs_new_protected:Npn \uiy_do:nn #1#2 { \use:c {#1} {#2} }
\ExplSyntaxOff

This time, I catch both the sequence of non-digits, and the number, as captured groups, \1 and \2. Each such occurrence is replaced by the macro \uiy_do:nn (the \c escape in this case indicates "build a comman"), then a begin-group (\cB) character { (this time, \c indicates the category code), then the non-digits (\1), then an end-group (\cE) character }, then another \cB{, the number, and a closing \cE}.

After that, the token list looks like \uiy_do:nn {ljksadflh} {1}. We then simply use its contents with \tl_use:N. The final step is to actually define \uiy_do:nn. Here, I defined it as simply building a command from #1, and giving it the argument #2. This very simple action could be done at the replacement step using \c{\1} for "build a command from the contents of group \1", and technically it would be slightly better, producing an "undefined control sequence" error if the relevant command is not defined. Another option for that error detection to happen is to replace \use:c {#1} {#2} by \cs_if_exist_use:cF {#1} { \msg_error:nnx { uiy } { undefined-command } } {#2}, with an appropriately defined error message.

Best Answer

Related Solutions

[Tex/LaTex] Is it possible to clear tikz/pgf options

[Tex/LaTex] Parse a string into tokens of numbers and not numbers

Related Question