Scheme Gemtext Reader

siiky

2022/07/05

2022/07/05

en

Yesterday I made a Scheme library to read Gemtext into a simple AST: a list of lines of text, headers, links, list blocks, or code blocks.

Text

some text

"some text"

Just a string, not tagged in any way. Empty lines are kept.

Headers

^(#+)\s+(.*)$

If *strict-gemtext-headers* is enabled, header lines of level > 3 are not considered headers.

title

"##### title" ; (w/ strict-gemtext-headers enabled)

'(header 5 "title") ; (w/ strict-gemtext-headers disabled)

## Links

=> Optional alt text

'(link "some-uri.gmi" "Optional alt text")

If there's no alt text, the empty string is used:

=> some-uri.gmi

'(link "some-uri.gmi" "")

## Lists

• item 1
• item 2

'(list "item 1"

   "item 2")

## Code blocks

(pretend there's no space between the three backticks)

some
pre-formatted
text

'(code "some optional alt text"

   "some"

   "pre-formatted"

   "text")

If there's no alt text, the empty string is used:

some
pre-formatted
text

'(code ""

   "some"

   "pre-formatted"

   "text")

## Example

Factorial

There are two steps to compute the factorial of a number:

• Compute the list of integers from 1 up to the number
• Multiply all the integers of the list

=> gemini://gemi.dev/cgi-bin/wp.cgi/view/en?Factorial | Factorial

Haskell code

Here's the code in Haskell:

fact n = prod [1..n]

'((header 1 "Factorial")

""

"There are two steps to compute the factorial of a number:"

""

(list "Compute the list of integers from 1 up to the number"

    "Multiply all the integers of the list")

""

(link "gemini://gemi.dev/cgi-bin/wp.cgi/view/en?Factorial" "")

(link "gemini://gemi.dev/cgi-bin/wp.cgi/view/en?Factorial" "Factorial")

""

(header 2 "Haskell code")

""

"Here's the code in Haskell:"

""

(code "hs"

    "fact n = prod [1..n]"))

## Output Patterns

(header level title)

(link uri alt-text)

(code alt-text . lines)

(list . items)