Table of Contents

• Preface
• Comparation Table
• Emacs: what you type is not what you see
• Short summary

Preface This article is a summary of two previous posts that you can read at these pages:

• “Vim: Study on constructing Regular Expressions to delete or reduce blank lines with Global Command”
• “Emacs: Study on constructing Regular Expressions to delete or reduce blank lines”

The topic of “regular expressions” in Vim and Emacs is well suited for a functional comparison across the four different scenarios covered in the above articles to which I refer for a description of the syntax.

Comparation Table

| Target | Vim | Emacs | | --- | --- | --- | | Delete “pure” blank lines | :g/^$/d | M-x flush-lines <RET> ^$ <RET> | | Delete blank lines with whitespace | :g/^\s*$/d | M-x flush-lines <RET> ^\s-*$ <RET> | | Reduce “pure” blank lines | :g/^$\n^$/d | M-x query-replace-regexp <RET> ^C-qC-j\{2,\} <RET> C-qC-j <RET> | | Reduce blank lines with whitespace | g/^\s*$\n^\s*$/d | ^\(^C-q<SPC>*C-qC-j\)\{2,\} <RET> C-qC-j <RET> |

Emacs: what you type is not what you see As explained in the article on Emacs, what you type is not what you see.

Below is a brief summary table for the operation of “reducing” blank lines, the third and fourth formulas in the above table, by distinguishing the keys pressed from the characters displayed.

| Type | Visualize | | --- | --- | | ^C-qC-j\{2,\} <RET> C-qC-j <RET> | ^^J\{2,\} → ^J | | ^\(^C-q<SPC>*C-qC-j\)\{2,\}<RET> C-qC-j <RET> | ^\(^ *^J\)\{2,\} → ^J |

Short summary The subject of regular expressions in Vim and Emacs shows several differences between the two editors.

I am unable to determine which implementation is the best one.

It is necessary, in any case, to consider that Emacs has a very good emulator of Vim, called Evil, that allows one to use the same regular expression language as the source editor.

Thank you for your attention.