7. 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 535; 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 535.

Listing 535 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.

7.1. Introduction to replacements

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

Example 143

Beginning with the code in Listing 536 and running the command

latexindent.pl -r replace1.tex

gives the output given in Listing 537.

Listing 536 replace1.tex

Before text, latexindent.pl,
after text.

Listing 537 replace1.tex default

Before text, latexindent.pl,
after text.

We note that in Listing 535, because lookForThis is set to 0, the specified replacement has not been made, and there is no difference between Listing 536 and Listing 537.

If we do wish to perform this replacement, then we can tweak the default settings of Listing 535 by changing lookForThis to 1; we perform this action in Listing 539, and run the command

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

which gives the output in Listing 538.

Listing 538 replace1.tex using Listing 539

Before text, pl.latexindent,
after text.

Listing 539 replace1.yaml

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

Note that in Listing 539 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.

7.2. 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.

7.3. Examples of replacements

Example 144

We begin with code given in Listing 540

Listing 540 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 542, and running the command

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

then we achieve the output in Listing 541.

Listing 541 colsep.tex using Listing 540

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

Listing 542 colsep.yaml

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

Note that in Listing 542, 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 542 more concise by exploring the substitution field. Using the settings in Listing 544 and running the command

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

then we achieve the output in Listing 543.

Listing 543 colsep.tex using Listing 544

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

Listing 544 colsep1.yaml

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

The code given in Listing 544 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 544, 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 544 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 145

We’ll keep working with the file in Listing 540 for this example.

Using the YAML in Listing 546, and running the command

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

then we achieve the output in Listing 545.

Listing 545 colsep.tex using Listing 546

multi-line!

Listing 546 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 546, 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 535. 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 548, and running the command

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

then we achieve the output in Listing 547.

Listing 547 colsep.tex using Listing 548

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

Listing 548 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 548 within the file in Listing 540. As it has looked for the string within Listing 548 after the indentation has been performed. After indentation, the string as written in Listing 548 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 545.

Example 146

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

Assuming that we start with the code in Listing 549, 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 549 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 551 and run the command

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

to receive the output given in Listing 550.

Listing 550 displaymath.tex using Listing 551

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 551 displaymath1.yaml

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

A few notes about Listing 551:

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 6.3, which we do in Listing 553; upon running the command

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

then we receive the output in Listing 552.

Listing 552 displaymath.tex using Listing 551 and Listing 553

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 553 equation.yaml

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

Example 147

This example is motivated by tex stackexchange question 490086. We begin with the code in Listing 554.

Listing 554 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 556, and run the command

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

which gives the output in Listing 555.

Listing 555 phrase.tex using Listing 556

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 556 hspace.yaml

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

The \h+ setting in Listing 556 say to replace at least one horizontal space with a single space.

Example 148

We begin with the code in Listing 557.

Listing 557 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 559 and running the command

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

which gives the output in Listing 558.

Listing 558 references.tex using Listing 559

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

Listing 559 reference.yaml

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

Referencing Listing 559, the | means or, we have used capture groups, together with an example of an optional pattern, (?:eq)?.

Example 149

Let’s explore the three replacement mode switches (see Table 4) in the context of an example that contains a verbatim code block, Listing 560; we will use the settings in Listing 561.

Listing 560 verb1.tex

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

Listing 561 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 562 – Listing 564

Listing 562 verb1-mod1.tex

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

Listing 563 verb1-rv-mod1.tex

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

Listing 564 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 562 indentation has been performed, and that the replacements specified in Listing 561 have been performed, even within the verbatim code block;

2. in Listing 563 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 564 indentation has not been performed, but that replacements have been performed, not respecting the verbatim code block.

See the summary within Table 4.

Example 150

Let’s explore the amalgamate field from Listing 535 in the context of the file specified in Listing 565.

Listing 565 amalg1.tex

one two three

Let’s consider the YAML files given in Listing 566 – Listing 568.

Listing 566 amalg1-yaml.yaml

replacements:
  -
    this: one
    that: 1

Listing 567 amalg2-yaml.yaml

replacements:
  -
    this: two
    that: 2

Listing 568 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 569 – Listing 571.

Listing 569 amalg1.tex using Listing 566

1 two three

Listing 570 amalg1.tex using Listing 566 and Listing 567

1 2 three

Listing 571 amalg1.tex using Listing 566 and Listing 567 and Listing 568

one two 3

We note that:

1. in Listing 569 the replacements from Listing 566 have been used;

2. in Listing 570 the replacements from Listing 566 and Listing 567 have both been used, because the default value of amalgamate is 1;

3. in Listing 571 only the replacements from Listing 568 have been used, because the value of amalgamate has been set to 0.

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