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 543; 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 543.

Listing 543 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 147

Beginning with the code in Listing 544 and running the command

latexindent.pl -r replace1.tex

gives the output given in Listing 545.

Listing 544 replace1.tex

Before text, latexindent.pl,
after text.

Listing 545 replace1.tex default

Before text, latexindent.pl,
after text.

We note that in Listing 543, because lookForThis is set to 0, the specified replacement has not been made, and there is no difference between Listing 544 and Listing 545.

If we do wish to perform this replacement, then we can tweak the default settings of Listing 543 by changing lookForThis to 1; we perform this action in Listing 547, and run the command

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

which gives the output in Listing 546.

Listing 546 replace1.tex using Listing 547

Before text, pl.latexindent,
after text.

Listing 547 replace1.yaml

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

Note that in Listing 547 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 148

We begin with code given in Listing 548

Listing 548 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 550, and running the command

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

then we achieve the output in Listing 549.

Listing 549 colsep.tex using Listing 550

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

Listing 550 colsep.yaml

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

Note that in Listing 550, 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 550 more concise by exploring the substitution field. Using the settings in Listing 552 and running the command

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

then we achieve the output in Listing 551.

Listing 551 colsep.tex using Listing 552

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

Listing 552 colsep1.yaml

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

The code given in Listing 552 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 552, 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 552 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 149

We’ll keep working with the file in Listing 548 for this example.

Using the YAML in Listing 554, and running the command

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

then we achieve the output in Listing 553.

Listing 553 colsep.tex using Listing 554

multi-line!

Listing 554 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 554, 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 543. 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 556, and running the command

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

then we achieve the output in Listing 555.

Listing 555 colsep.tex using Listing 556

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

Listing 556 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 556 within the file in Listing 548. As it has looked for the string within Listing 556 after the indentation has been performed. After indentation, the string as written in Listing 556 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 553.

Example 150

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

Assuming that we start with the code in Listing 557, 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 557 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 559 and run the command

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

to receive the output given in Listing 558.

Listing 558 displaymath.tex using Listing 559

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 559 displaymath1.yaml

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

A few notes about Listing 559:

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 561; upon running the command

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

then we receive the output in Listing 560.

Listing 560 displaymath.tex using Listing 559 and Listing 561

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 561 equation.yaml

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

Example 151

This example is motivated by tex stackexchange question 490086. We begin with the code in Listing 562.

Listing 562 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 564, and run the command

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

which gives the output in Listing 563.

Listing 563 phrase.tex using Listing 564

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 564 hspace.yaml

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

The \h+ setting in Listing 564 say to replace at least one horizontal space with a single space.

Example 152

We begin with the code in Listing 565.

Listing 565 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 567 and running the command

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

which gives the output in Listing 566.

Listing 566 references.tex using Listing 567

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

Listing 567 reference.yaml

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

Referencing Listing 567, the | means or, we have used capture groups, together with an example of an optional pattern, (?:eq)?.

Example 153

Let’s explore the three replacement mode switches (see Table 4) in the context of an example that contains a verbatim code block, Listing 568; we will use the settings in Listing 569.

Listing 568 verb1.tex

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

Listing 569 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 570 – Listing 572

Listing 570 verb1-mod1.tex

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

Listing 571 verb1-rv-mod1.tex

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

Listing 572 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 570 indentation has been performed, and that the replacements specified in Listing 569 have been performed, even within the verbatim code block;

2. in Listing 571 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 572 indentation has not been performed, but that replacements have been performed, not respecting the verbatim code block.

See the summary within Table 4.

Example 154

Let’s explore the amalgamate field from Listing 543 in the context of the file specified in Listing 573.

Listing 573 amalg1.tex

one two three

Let’s consider the YAML files given in Listing 574 – Listing 576.

Listing 574 amalg1-yaml.yaml

replacements:
  -
    this: one
    that: 1

Listing 575 amalg2-yaml.yaml

replacements:
  -
    this: two
    that: 2

Listing 576 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 577 – Listing 579.

Listing 577 amalg1.tex using Listing 574

1 two three

Listing 578 amalg1.tex using Listing 574 and Listing 575

1 2 three

Listing 579 amalg1.tex using Listing 574 and Listing 575 and Listing 576

one two 3

We note that:

1. in Listing 577 the replacements from Listing 574 have been used;

2. in Listing 578 the replacements from Listing 574 and Listing 575 have both been used, because the default value of amalgamate is 1;

3. in Listing 579 only the replacements from Listing 576 have been used, because the value of amalgamate has been set to 0.

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