Batch text processing with Perl 6

Question

I am reading Think Perl 6 by Laurent Rosenfeld, with Allen B. Downey recently which is a very good reading.

It has its .tex files available in github here.

It has code examples like this:

I believe it would be very useful to have the code blocks colored like this:

For this to happen we have to batch process all .tex files contained in the repository above. For this to happen we have to convert the latex code:

\begin{verbatim}
        say 42 ==  42;           # True
        say 42 ==  42.0;         # True
        say 42 ===  42;          # True
        say 42 === 42.0;         # False
\end{verbatim}


\begin{verbatim}
$x eq $y            # $x is string-wise equal to $y
$x ne $y            # $x is string-wise not equal to $y
$x gt $y            # $x is greater than $y (alphabetically after)
$x lt $y            # $x is less than $y (alphabetically before)
$x ge $y            # $x is greater than or equal to $y
$x le $y            # $x is less than or equal to $y
$x eqv $y           # $x is truly equivalent to $y
\end{verbatim}

TO

\begin{minted}{perl6}
        say 42 ==  42;           # True
        say 42 ==  42.0;         # True
        say 42 ===  42;          # True
        say 42 === 42.0;         # False
\end{minted}


\begin{minted}{perl6}
$x eq $y            # $x is string-wise equal to $y
$x ne $y            # $x is string-wise not equal to $y
$x gt $y            # $x is greater than $y (alphabetically after)
$x lt $y            # $x is less than $y (alphabetically before)
$x ge $y            # $x is greater than or equal to $y
$x le $y            # $x is less than or equal to $y
$x eqv $y           # $x is truly equivalent to $y
\end{minted}

I want to accomplish this with Perl 6. Here is how I plan to do.

THIS IS DUMMY CODE

# First I want to skim all the .tex files in the cloned repo (with git) 

for dir("ThinkPerl6/book") ->$file {
  say $file if $file~~/\.tex/;
}

# Read each .tex file and modify, replace `\begin{verbatim}` with `\begin{minted}{perl6}`

for "$file.tex".IO.lines -> $line {
  substitute with "\begin{minted}{perl6}" if $line ~~/\\begin\{verbatim\}/;
}

# Read each .tex file and modify, replace `\end{verbatim}` with `\end{minted}`

for "$file.tex".IO.lines -> $line {
  substitute with "\end{minted}" if $line ~~/\\end\{verbatim\}/;
}

I could not go beyond that. Any help? Use of regexp would be very helpful.

Best regards,

Suman

Answer 1

You need to do the following steps:

• create a copy of each line with a substitution applied. You can use the subst method for that
• write the modified copy to a new file (maybe with extension .new added or so)
• optionally, move the .new to override the original file. See this example for inspiration.

I hope this helps.

Answer 2

Here is one implementation of moritz's first two bullet points.

my $fh-out = open "$file.new.tex", :w; # Create a new file

# Read in old file, line by line
for "$file.tex".IO.lines -> $line is copy {

    # Make changes, if needed
    $line.=subst('\begin\{verbatim\}','\begin{minted}{perl6}');
    $line.=subst('\end\{verbatim\}','\end{minted}');

    # Print line to new file
    $fh-out.put: $line;
}