MathB

MathB is a mathematics pastebin software that powers MathB.in. It is a web-based service meant for sharing snippets of mathematical text with others on the world wide web. Visit https://mathb.in/ to use the mathematics pastebin.

Contents

• Features
• Quick Start
• Custom Directory Paths
• Data Files
• Runtime Options
• Templates Files
• Static Files
• Live Directory
• Print
• Save PDF
• History
• License
• Support
• Channels
• More

Features

• Minimalist user interface that has not changed much over a decade.
• Live preview of Markdown and LaTeX content as it is typed.
• Support for mixing Markdown and LaTeX code freely.
• Printing a post to PDF or paper prints only the rendered content.
• All UI elements apart from rendered content are excluded from prints.
• No web cookies.
• No web analytics.

Quick Start

This section explains how to run this project locally. The steps assume a macOS, Debian, or Debian-based Linux distribution. However, it should be possible to adapt these steps for another operating system.

1. Install SBCL and Git.

   On macOS, enter the following command if you have Homebrew:

   brew install sbcl git

   On Debian, Ubuntu, or another Debian-based Linux system, enter the following command:

   sudo apt-get update
   sudo apt-get install sbcl git

2. Install Quicklisp with the following commands:

   curl -O https://beta.quicklisp.org/quicklisp.lisp
   sbcl --load quicklisp.lisp --eval "(quicklisp-quickstart:install)" --quit
   sbcl --load ~/quicklisp/setup.lisp --eval "(ql:add-to-init-file)" --quit

3. From here on, we assume that all commands are being run in the top-level directory of this project. Set up dependencies necessary to run this project by running this command within the top-level directory of this project:

   make live

   This creates a _live directory within the current directory and copies all necessary dependencies to it.

4. Create data and log directories:

   sudo mkdir -p /opt/data/mathb/ /opt/log/mathb/
   sudo cp -R meta/data/* /opt/data/mathb/
   sudo chown -R "$USER" /opt/data/mathb/ /opt/log/mathb/

   By default, MathB reads post data from and writes posts to /opt/data/mathb/. It writes logs to /opt/log/mathb/ by default. The next section explains how to make it use custom directory paths.

5. Run MathB with the following command:

   sbcl --load mathb.lisp

6. Visit http://localhost:4242/ with a web browser to use MathB.

After starting MathB in this manner, click on the various navigation links and make a new post to confirm that MathB is working as expected.

Custom Directory Paths

In the previous section, we created a data directory at /opt/data/mathb/ and a log directory at /opt/log/mathb/. By default, MathB writes new posts to and reads posts from this directory path. To make it use a different path for the data directory, set the variable named *data-directory* before loading it. Similarly, set the variable named *log-directory* to specify a different path for the log directory. The following steps demonstrate how to do this:

1. Create data directory at a custom path, say, at ~/data:

   mkdir -p ~/data/ ~/log/
   cp -R meta/data/* ~/data/

2. Run MathB with the following command:

   sbcl --eval '(defvar *data-directory* "~/data/")' \
        --eval '(defvar *log-directory* "~/log/")' \
        --load mathb.lisp

3. Visit http://localhost:4242/ with a web browser to use MathB.

After starting MathB in this manner, click on the various navigation links and make a new post to confirm that MathB is working as expected.

Data Files

The data directory contains the following files:

• opt.lisp: This file contains a property list that can be modified to alter the behaviour of MathB. This is explained in detail in the next section.

• slug.txt: This file contains the ID of the latest post successfully saved.

• post/X/Y/*.txt: These files contain the actual posts submitted by users where X and Y are placeholders for two integers explained shortly. Each .txt file contains a post submitted by a user.

In the last point, the placeholder X is the post ID divided by 1000000. The placeholder Y is the post ID divided by 1000. For example, for a post with ID 1, X is 0 and Y is 0, so a post with this ID is saved at post/0/0/1.txt. For a more illustrative example, consider a post with with ID 2301477. Now X is 2 and Y is 2301, so a post with this ID is saved at post/2/2301/2301477.txt.

Let us call each X directory a short-prefix directory and each Y directory under it a long-prefix directory. As a result of the calculation explained above, each short-prefix directory contains a maximum of 1000 long-prefix directories and each long-prefix directory contains a maximum of 1000 post files. Thus, each short-prefix directory contains a maximum of one million post files under it.

Runtime Options

MathB reads runtime properties from opt.lisp. This file contains a property list. Each property in this list is followed by a value for that property. This property list may be used to alter the behaviour of MathB. A list of all supported properties and their descriptions is provided below.

• :lock-down (default is nil): A value of t makes MathB run in lock-down mode, i.e., existing posts cannot be viewed and new posts cannot be submitted.

• :read-only (default is nil): A value of t makes MathB run in read-only mode, i.e., old posts can be viewed but new posts cannot be made. If the values of both this property and the previous property are nil, then MathB runs normally in read-write mode.

• :min-title-length (default is 0): The minimum number of characters allowed in the title field.

• :max-title-length (default is 120): The maximum number of characters allowed in the title field.

• :min-name-length (default is 0): The minimum number of characters allowed in the name field.

• :max-name-length (default is 120): The maximum number of characters allowed in the name field.

• :min-code-length (default is 1): The minimum number of characters allowed in the code field.

• :max-code-length (default is 10000): The maximum number of characters allowed in the code field.

• :global-post-interval (default is 0): The minimum interval (in seconds) required between two consecutive successful posts.

  Example: If this value is 10 and one client submits a new post at 10:00:00 and another client submits a post at 10:00:07, the post of the second client is rejected with an error message that they must wait for 3 more seconds before submitting the post. An attempt to submit the post at 10:00:10 or later would succeed, provided that no other client submitted another post between 10:00:10 and the second client's attempt to make a post.

• :client-post-interval (default is 0): The minimum interval (in seconds) between two consecutive successful posts allowed from the same client.

  Example: If this value is 10 and one client submits a new post at 10:00:00, then the same client is allowed to make the next successful post submission at 10:00:10 or later. If the same client submits another post at 10:00:07, the post is rejected with an error message that they must wait for 3 more seconds before submitting the post. This does not affect the posting behaviour for other clients. For example, another client can successfully submit their post at 10:00:07 while the first client cannot.

• :expect (default is nil): A list of strings. At least one string from this list must occur in the submitted code field.

  Example: If this value is ("\(" "\[") and the submitted post contains \[ 1 + 1 = 2. \] in the code field, then the post is accepted successfully. However, if the submitted code contains only 1 + 1 = 2, then the post is rejected because neither the string "\(" nor the string "\[" occurs in the code field of this submission.

• :block (default is nil): A list of strings that are not allowed in a post. If a post contains any string in this list, the post is rejected and the input form is returned intact to the client.

  Example: If this value is ("berk" "naff" "xxx") and a client posts content which contains the string xxx in any field (code, title, or name), the post is rejected.

• :ban (default is nil): A list of IPv4 or IPv6 address prefixes. If the address of the remote client (as it appears in the logs) matches any prefix in this list, the post from the client is rejected. The prefixes must be expressed as simple string literals. CIDRs, globs, regular expressions, etc. are not supported. A dollar sign ($) at the end of a prefix string matches the end of the client's address string.

  Example: Let us consider a value of ("10.1." "10.2.0.2" "10.3.0.2$") for this property. If a client from IP address 10.1.2.3 submits a post, it is rejected because the prefix 10.1. matches this IP address. If a client from IP address 10.2.0.23 submits a post, it is rejected because the prefix 10.2.0.2 matches this IP address. If a client from IP address 10.3.0.2 submits a post, it is rejected because the prefix 10.3.0.2$ matches this IP address. If a client from IP address 10.3.0.23 submits a post, it is accepted because none of the prefixes match this IP address.

• :protect (default is 0): The maximum ID of protected posts. If MathB determines that the post ID of the next post is less than or equal to this value, then it rejects the post. Setting this property is almost never required. However, it is provided for paranoid administrators who might worry what would happen if the data file slug.txt ever becomes corrupt. This property ensures that in case this data file ever becomes corrupt, MathB would never ever overwrite old posts with IDs less than or equal to the number set for this property.

  Example: Let us assume that the current value in slug.txt is 1200. Now normally, the next time a client submits a new post, their post would be saved with an ID of 1201 and the value in slug.txt would be incremented to 1201. But instead, let us assume that due to an unforeseen scenario (say, a bug in MathB or a hardware failure), the value in slug.txt is corrupted to 12. With a value of 0 for :protect, MathB would overwrite an existing post at post/0/0/13.txt. However, with a value of say, 100 for :protect, MathB would refuse to overwrite the existing port.

If a property name is missing from this file or if the file itself is missing, then the default value of the property mentioned within parentheses above is used.

Whenever a post is rejected due to a runtime option, the entire input form is returned intact to the client with an error message, so that they can fix the errors or wait for the suggested post interval and resubmit the post again.

The property values in opt.lisp may be modified at any time, even while MathB is running. It is not necessary to restart MathB after changing property values in opt.lisp. The changes are picked up automatically while processing the next HTTP POST request.

Template Files

There are two template files to generate the HTML pages sent to the clients:

• web/html/mathb.html: This template file is used to generate the HTML response for the home page, a mathematical snippet page, as well as an HTTP response page when the post is rejected due to a validation error.

• web/html/error.html: This template file is used to generate HTTP error pages.

A template file may be modified at any time, even while MathB is running. It is not necessary to restart MathB after changing a template file. The changes are picked up automatically while processing the next HTTP request.

Static Files

There are three types of static files that MathB uses to for its HTML pages:

• web/js/: This directory contains the JavaScript files that perform input rendering as a user types out content in the input form.

• web/css/: This directory contains the stylesheets for the HTML pages generated by MathB.

• web/img/: This directory contains the favicons for the website. These icons are generated using a LaTeX project in the meta/logo/ directory.

A static file may be modified at any time, even while MathB is running. It is not necessary to restart MathB after adding, deleting, or editing a static file. However, it is necessary to run make live (in the top-level directory of the project) to copy the static files to the live directory (explained in the next section) from which MathB serves the static files.

Live Directory

MathB needs to pull additional JavaScript libraries named TeXMe, Marked, and MathJax that are essential for rendering Markdown and LaTeX input. This is done by running the following command in the top-level directory of this project:

make live

The above command creates a _live directory from scratch, copies the static files to it, then pulls the additional JavaScript libraries into it, and sets up the _live directory, so that MathB can serve the static files from it.

The live directory should never be modified directly because every make live run deletes the entire directory and creates it from scratch again. Any modification necessary should be made to the template files or static files explained in the previous two sections.

Print

While the primary purpose of this project is to allow users to write mathematical snippets, save them, and share a link to them with others, the stylesheet used in this project takes special care to allow printing beautifully rendered pages to paper.

When a MathB page is printed, only the rendered content appears in the print. The input form, buttons, navigation links, and other user interface elements do not appear in the print.

Save PDF

It is possible to turn a MathB post into a PDF file using the printing facility of most web browsers running on a desktop or laptop. The exact steps to save a web page as PDF vary from browser to browser but the steps to do so look roughly like this:

• Select File > Print from the web browser menu.
• Then in the print window or dialog box that comes up, deselect/disable the options to print headers and footers.
• Finally, choose the option to save a PDF.

If everything works as expected, the saved PDF should contain only the rendered content with all mathematical formulas rendered properly. The web pages generated by this project use special styling rules to ensure that the input form, buttons, navigation links, and other user interface elements do not appear in saved PDF.

History

MathB.in is the oldest mathematics pastebin that is still online and serving its community of users. It isn't the first mathematics pastebin though. It's the second. The first pastebin was written by Mark A. Stratman. It was hosted at the domain mathbin.net until 2020.

MathB.in was born on Sunday, 25 March 2012, after a single night of furious coding. This was a result of stumbling upon math.stackexchange.com the previous night which used MathJax to render mathematics formula on the web browser. Thanks to that chance encounter with MathJax, the rest of the Saturday night was spent in coding a new mathematics pastebin using MathJax and PHP. After coding all through the night, registering a new domain name, and setting up a website, MathB.in was released early Sunday morning.

The current version of MathB.in no longer runs on PHP. It has been rewritten in Common Lisp since then. See the blog post MathB.in Turns 10 for more details about the history of MathB.in.

License

This is free and open source software. You can use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of it, under the terms of the MIT License. See LICENSE.md for details.

This software is provided "AS IS", WITHOUT WARRANTY OF ANY KIND, express or implied. See LICENSE.md for details.

Support

To report bugs, suggest improvements, or ask questions, create issues.

Channels

The author of this project hangs out at the following places online:

• susam.net on the Web
• @susam on Twitter
• @susam on GitHub
• #susam on Libera
• #susam on Matrix

You are welcome to subscribe to, follow, or join one or more of the above channels to receive updates from the author or ask questions about this project.

More

If you like this project, check out related projects TeXMe and Muboard.