5. The -r, -rv and -rr switches

You can instruct latexindent.pl to perform replacements/substitutions on your file by using any of the -r, -rv or -rr switches:

• the -r switch will perform indentation and replacements, not respecting verbatim code blocks;

• the -rv switch will perform indentation and replacements, and will respect verbatim code blocks;

• the -rr switch will not perform indentation, and will perform replacements not respecting verbatim code blocks.

We will demonstrate each of the -r, -rv and -rr switches, but a summary is given in Table 4.

Table 4 The replacement mode switches

switch	indentation?	respect verbatim?
-r	yes	no
-rv	yes	yes
-rr	no	no

The default value of the replacements field is shown in Listing 511; as with all of the other fields, you are encouraged to customise and change this as you see fit. The options in this field will only be considered if the -r, -rv or -rr switches are active; when discussing YAML settings related to the replacement-mode switches, we will use the style given in Listing 511.

Listing 511 replacements

replacements:
  - amalgamate: 1
  - this: latexindent.pl
    that: pl.latexindent
    lookForThis: 0
    when: before

The first entry within the replacements field is amalgamate, and is optional; by default it is set to 1, so that replacements will be amalgamated from each settings file that you specify. As you’ll see in the demonstrations that follow, there is no need to specify this field.

You’ll notice that, by default, there is only one entry in the replacements field, but it can take as many entries as you would like; each one needs to begin with a - on its own line.

5.1. Introduction to replacements

Let’s explore the action of the default settings, and then we’ll demonstrate the feature with further examples.

Example 144

Beginning with the code in Listing 512 and running the command

latexindent.pl -r replace1.tex

gives the output given in Listing 513.

Listing 512 replace1.tex

Before text, latexindent.pl,
after text.

Listing 513 replace1.tex default

Before text, latexindent.pl,
after text.

We note that in Listing 511, because lookForThis is set to 0, the specified replacement has not been made, and there is no difference between Listing 512 and Listing 513.

If we do wish to perform this replacement, then we can tweak the default settings of Listing 511 by changing lookForThis to 1; we perform this action in Listing 515, and run the command

latexindent.pl -r replace1.tex -l=replace1.yaml

which gives the output in Listing 514.

Listing 514 replace1.tex using Listing 515

Before text, pl.latexindent,
after text.

Listing 515 replace1.yaml

replacements:
  - 
    amalgamate: 0
  -
    this: latexindent.pl
    that: pl.latexindent
    lookForThis: 1

Note that in Listing 515 we have specified amalgamate as 0 so that the default replacements are overwritten.

We haven’t yet discussed the when field; don’t worry, we’ll get to it as part of the discussion in what follows.

5.2. The two types of replacements

There are two types of replacements:

1. string-based replacements, which replace the string in this with the string in that. If you specify this and you do not specify that, then the that field will be assumed to be empty.

2. regex-based replacements, which use the substitution field.

We will demonstrate both in the examples that follow.

latexindent.pl chooses which type of replacement to make based on which fields have been specified; if the this field is specified, then it will make string-based replacements, regardless of if substitution is present or not.

5.3. Examples of replacements

Example 145

We begin with code given in Listing 516

Listing 516 colsep.tex

\begin{env}
1 2 3\arraycolsep=3pt
4 5 6\arraycolsep=5pt
\end{env}

Let’s assume that our goal is to remove both of the arraycolsep statements; we can achieve this in a few different ways.

Using the YAML in Listing 518, and running the command

latexindent.pl -r colsep.tex -l=colsep.yaml

then we achieve the output in Listing 517.

Listing 517 colsep.tex using Listing 518

\begin{env}
	1 2 3
	4 5 6
\end{env}

Listing 518 colsep.yaml

replacements:
  -
    this: \arraycolsep=3pt
  -
    this: \arraycolsep=5pt

Note that in Listing 518, we have specified two separate fields, each with their own ‘this’ field; furthermore, for both of the separate fields, we have not specified ‘that’, so the that field is assumed to be blank by latexindent.pl;

We can make the YAML in Listing 518 more concise by exploring the substitution field. Using the settings in Listing 520 and running the command

latexindent.pl -r colsep.tex -l=colsep1.yaml

then we achieve the output in Listing 519.

Listing 519 colsep.tex using Listing 520

\begin{env}
	1 2 3
	4 5 6
\end{env}

Listing 520 colsep1.yaml

replacements:
  -
    substitution: s/\\arraycolsep=\d+pt//sg

The code given in Listing 520 is an example of a regular expression, which we may abbreviate to regex in what follows. This manual is not intended to be a tutorial on regular expressions; you might like to read, for example, (Friedl, n.d.) for a detailed covering of the topic. With reference to Listing 520, we do note the following:

• the general form of the substitution field is s/regex/replacement/modifiers. You can place any regular expression you like within this;

• we have ‘escaped’ the backslash by using \\

• we have used \d+ to represent at least one digit

• the s modifier (in the sg at the end of the line) instructs latexindent.pl to treat your file as one single line;

• the g modifier (in the sg at the end of the line) instructs latexindent.pl to make the substitution globally throughout your file; you might try removing the g modifier from Listing 520 and observing the difference in output.

You might like to see https://perldoc.perl.org/perlre.html#Modifiers for details of modifiers; in general, I recommend starting with the sg modifiers for this feature.

Example 146

We’ll keep working with the file in Listing 516 for this example.

Using the YAML in Listing 522, and running the command

latexindent.pl -r colsep.tex -l=multi-line.yaml

then we achieve the output in Listing 521.

Listing 521 colsep.tex using Listing 522

multi-line!

Listing 522 multi-line.yaml

replacements:
  -
    this: |-
     \begin{env}
     1 2 3\arraycolsep=3pt
     4 5 6\arraycolsep=5pt
     \end{env}
    that: 'multi-line!'

With reference to Listing 522, we have specified a multi-line version of this by employing the literal YAML style |-. See, for example, https://stackoverflow.com/questions/3790454/in-yaml-how-do-i-break-a-string-over-multiple-lines for further options, all of which can be used in your YAML file.

This is a natural point to explore the when field, specified in Listing 511. This field can take two values: before and after, which respectively instruct latexindent.pl to perform the replacements before indentation or after it. The default value is before.

Using the YAML in Listing 524, and running the command

latexindent.pl -r colsep.tex -l=multi-line1.yaml

then we achieve the output in Listing 523.

Listing 523 colsep.tex using Listing 524

\begin{env}
	1 2 3\arraycolsep=3pt
	4 5 6\arraycolsep=5pt
\end{env}

Listing 524 multi-line1.yaml

replacements:
  -
    this: |-
     \begin{env}
     1 2 3\arraycolsep=3pt
     4 5 6\arraycolsep=5pt
     \end{env}
    that: 'multi-line!'
    when: after

We note that, because we have specified when: after, that latexindent.pl has not found the string specified in Listing 524 within the file in Listing 516. As it has looked for the string within Listing 524 after the indentation has been performed. After indentation, the string as written in Listing 524 is no longer part of the file, and has therefore not been replaced.

As a final note on this example, if you use the -rr switch, as follows,

latexindent.pl -rr colsep.tex -l=multi-line1.yaml

then the when field is ignored, no indentation is done, and the output is as in Listing 521.

Example 147

An important part of the substitution routine is in capture groups.

Assuming that we start with the code in Listing 525, let’s assume that our goal is to replace each occurrence of $$...$$ with \begin{equation*}...\end{equation*}. This example is partly motivated by tex stackexchange question 242150.

Listing 525 displaymath.tex

before text $$a^2+b^2=4$$ and $$c^2$$

$$
d^2+e^2 = f^2
$$
and also $$ g^2
$$ and some inline math: $h^2$

We use the settings in Listing 527 and run the command

latexindent.pl -r displaymath.tex -l=displaymath1.yaml

to receive the output given in Listing 526.

Listing 526 displaymath.tex using Listing 527

before text \begin{equation*}a^2+b^2=4\end{equation*} and \begin{equation*}c^2\end{equation*}

\begin{equation*}
	d^2+e^2 = f^2
\end{equation*}
and also \begin{equation*} g^2
\end{equation*} and some inline math: $h^2$

Listing 527 displaymath1.yaml

replacements:
  -
    substitution: |-
     s/\$\$
       (.*?)
       \$\$/\\begin{equation*}$1\\end{equation*}/sgx

A few notes about Listing 527:

1. we have used the x modifier, which allows us to have white space within the regex;

2. we have used a capture group, (.*?) which captures the content between the $$...$$ into the special variable, $1;

3. we have used the content of the capture group, $1, in the replacement text.

See https://perldoc.perl.org/perlre.html#Capture-groups for a discussion of capture groups.

The features of the replacement switches can, of course, be combined with others from the toolkit of latexindent.pl. For example, we can combine the poly-switches of Section 4.3, which we do in Listing 529; upon running the command

latexindent.pl -r -m displaymath.tex -l=displaymath1.yaml,equation.yaml

then we receive the output in Listing 528.

Listing 528 displaymath.tex using Listing 527 and Listing 529

before text%
\begin{equation*}%
	a^2+b^2=4%
\end{equation*}%
and%
\begin{equation*}%
	c^2%
\end{equation*}

\begin{equation*}
	d^2+e^2 = f^2
\end{equation*}
and also%
\begin{equation*}%
	g^2
\end{equation*}%
and some inline math: $h^2$

Listing 529 equation.yaml

modifyLineBreaks:
    environments:
        equation*:
            BeginStartsOnOwnLine: 2
            BodyStartsOnOwnLine: 2
            EndStartsOnOwnLine: 2
            EndFinishesWithLineBreak: 2
        

Example 148

This example is motivated by tex stackexchange question 490086. We begin with the code in Listing 530.

Listing 530 phrase.tex

phrase 1       phrase 2 phrase 3             phrase 100

phrase 1       phrase 2 phrase 3             phrase 100

phrase 1       phrase 2 phrase 3             phrase 100

phrase 1       phrase 2 phrase 3             phrase 100

Our goal is to make the spacing uniform between the phrases. To achieve this, we employ the settings in Listing 532, and run the command

latexindent.pl -r phrase.tex -l=hspace.yaml

which gives the output in Listing 531.

Listing 531 phrase.tex using Listing 532

phrase 1 phrase 2 phrase 3 phrase 100

phrase 1 phrase 2 phrase 3 phrase 100

phrase 1 phrase 2 phrase 3 phrase 100

phrase 1 phrase 2 phrase 3 phrase 100

Listing 532 hspace.yaml

replacements:
  -
    substitution: s/\h+/ /sg

The \h+ setting in Listing 532 say to replace at least one horizontal space with a single space.

Example 149

We begin with the code in Listing 533.

Listing 533 references.tex

equation \eqref{eq:aa} and Figure  \ref{fig:bb}
and table~\ref{tab:cc}

Our goal is to change each reference so that both the text and the reference are contained within one hyperlink. We achieve this by employing Listing 535 and running the command

latexindent.pl -r references.tex -l=reference.yaml

which gives the output in Listing 534.

Listing 534 references.tex using Listing 535

\hyperref{equation \ref*{eq:aa}} and \hyperref{Figure \ref*{fig:bb}}
and \hyperref{table \ref*{tab:cc}}

Listing 535 reference.yaml

replacements:
  -
    substitution: |-
      s/(
        equation
        |
        table
        |
        figure
        |
        section
      )
      (\h|~)*
      \\(?:eq)?
      ref\{(.*?)\}/\\hyperref{$1 \\ref\*{$3}}/sgxi

Referencing Listing 535, the | means or, we have used capture groups, together with an example of an optional pattern, (?:eq)?.

Example 150

Let’s explore the three replacement mode switches (see Table 4) in the context of an example that contains a verbatim code block, Listing 536; we will use the settings in Listing 537.

Listing 536 verb1.tex

\begin{myenv}
body of verbatim
\end{myenv}
some verbatim
\begin{verbatim}
    body
        of
      verbatim
 text
\end{verbatim}
text

Listing 537 verbatim1.yaml

replacements:
  -
    this: 'body'
    that: 'head'

Upon running the following commands,

latexindent.pl -r verb1.tex -l=verbatim1.yaml -o=+mod1
latexindent.pl -rv verb1.tex -l=verbatim1.yaml -o=+-rv-mod1
latexindent.pl -rr verb1.tex -l=verbatim1.yaml -o=+-rr-mod1

we receive the respective output in Listing 538 – Listing 540

Listing 538 verb1-mod1.tex

\begin{myenv}
	head of verbatim
\end{myenv}
some verbatim
\begin{verbatim}
    head
        of
      verbatim
 text
\end{verbatim}
text

Listing 539 verb1-rv-mod1.tex

\begin{myenv}
	head of verbatim
\end{myenv}
some verbatim
\begin{verbatim}
    body
        of
      verbatim
 text
\end{verbatim}
text

Listing 540 verb1-rr-mod1.tex

\begin{myenv}
head of verbatim
\end{myenv}
some verbatim
\begin{verbatim}
    head
        of
      verbatim
 text
\end{verbatim}
text

We note that:

1. in Listing 538 indentation has been performed, and that the replacements specified in Listing 537 have been performed, even within the verbatim code block;

2. in Listing 539 indentation has been performed, but that the replacements have not been performed within the verbatim environment, because the rv switch is active;

3. in Listing 540 indentation has not been performed, but that replacements have been performed, not respecting the verbatim code block.

See the summary within Table 4.

Example 151

Let’s explore the amalgamate field from Listing 511 in the context of the file specified in Listing 541.

Listing 541 amalg1.tex

one two three

Let’s consider the YAML files given in Listing 542 – Listing 544.

Listing 542 amalg1-yaml.yaml

replacements:
  -
    this: one
    that: 1

Listing 543 amalg2-yaml.yaml

replacements:
  -
    this: two
    that: 2

Listing 544 amalg3-yaml.yaml

replacements:
  - 
    amalgamate: 0
  -
    this: three
    that: 3

Upon running the following commands,

latexindent.pl -r amalg1.tex -l=amalg1-yaml
latexindent.pl -r amalg1.tex -l=amalg1-yaml,amalg2-yaml
latexindent.pl -r amalg1.tex -l=amalg1-yaml,amalg2-yaml,amalg3-yaml

we receive the respective output in Listing 545 – Listing 547.

Listing 545 amalg1.tex using Listing 542

1 two three

Listing 546 amalg1.tex using Listing 542 and Listing 543

1 2 three

Listing 547 amalg1.tex using Listing 542 and Listing 543 and Listing 544

one two 3

We note that:

1. in Listing 545 the replacements from Listing 542 have been used;

2. in Listing 546 the replacements from Listing 542 and Listing 543 have both been used, because the default value of amalgamate is 1;

3. in Listing 547 only the replacements from Listing 544 have been used, because the value of amalgamate has been set to 0.

Friedl, Jeffrey E. F. n.d. Mastering Regular Expressions.