SEAM

Symbolic Expressions As Markup.

Why

Because all markup is terrible, especially XML/SGML and derivatives.

But mainly, for easier static markup code generation, such as by macros and code includes and such.

Try it out

This may be used as a Rust library, such as from within a server, generating HTML (or any other supported markup) before it is served to the client. Personally, I just use the seam binary to statically generate my personal websites through a Makefile.

Read the USAGE.md file for code examples and documentation.

Current Formats

• XML (--xml; including: SVG, MathML)
• HTML (--html; SGML)
• CSS (--css)
• JSON (--json)
• JavaScript (--js; written as s-expressions)
• SExp (--sexp; S-expression, basically a macro expansion utility)
• Plain Text (--text; renders escaped strings to text)

Installation

You may clone the repo, then build and install by

git clone git://git.knutsen.co/seam
cd seam
cargo build --release
cargo install --path .

Or install it from crates.io

cargo install seam

Either way, you'll need the Rust (nightly) compiler and along with it, comes cargo.

Using The Binary

You may use it by passing in a file and piping from STDOUT.

seam test.sex --html > test.html

test.sex contains your symbolic-expressions, which is used to generate HTML, saved in test.html.

Likewise, you may read from STDIN

seam --html < example.sex > example.html
# ... same as
cat example.sex | seam --html > example.html

You may also use here-strings or here-docs, if your shell supports it.

seam --html <<< "(p Hello World)"
#stdout:
#   <!DOCTYPE html>
#   <html>
#   <head></head>
#   <body>
#   <p>Hello World</p>
#   </body>
#   </html>

seam --html --nodocument <<< "(p Hello World)"
#stdout:
#   <p>Hello World</p>

seam --xml <<< '(para Today is a day in (%date "%B, year %Y").)'
#stdout:
#   <?xml version="1.0" encoding="UTF-8" ?>
#   <para>Today is a day in November, year 2020.</para>

seam --sexp <<< '(hello (%define subject world) %subject)'
#stdout:
#   (hello world)

To run a file only for what its macros do, such as writing files with %write, use seam run, which reports each action like make does:

seam run build.sex
#stdout:
#   write public/index.html
#   ...

Checklist

• Literate mode for parser+lexer, where string nodes are not escaped and parentheses are converted to symbols. The only time strings are escaped and parentheses make lists is inside a (% and ) pair, i.e. when calling a macro. So hello world (earth) (%do (p letter "\x61")) "\x61" turns in to (in HTML mode) hello world <earth></earth> <p>hi a</p> a normally, but in literate (HTML) mode turns into hello world (earth) <p>letter a</p> "\x61". Parentheses and quotes have been preserved. Markdown source in (%markdown ...) should be parsed as literate files by default. Provide command line --literate option; %include and %embed should also have options for enabling literate mode.
• Way to match on unknown keywords in attributes, examples when (%define dict (:a 1 :b 2 :c 3)): - (%for (kw val) in (%items %dict) (%log %kw = %val)) - (%for kw in (%keys %dict) (%log %kw = (%get %kw %dict))) - (%for val in (%values %dict) (%log ___ = %val))
• Extend %get to work with slicing (%get (1 3) (a b c d e)) becomes b c d; negative indices (%get -1 (a b c)) becomes c.
• Shell-style ${var:...} string manipulation, written %{var:...}.
• %while, %take, %drop, %split on symbols in lists, %intercalate.
• (%basename :suffix "txt" /path/file.txt) (-> file), (%dirname /path/file.txt) (-> /path) and (%extension /path/file.txt) (-> txt), macros for paths.
• %path/... macros: cwd, this, here, join, split, stem, with-extension, normalise, canonical, absolute, relative, exists, is-file and is-directory.
• seam run file.sex, running a file for its side effects (%write, %exec), reported on STDOUT like make.
• Math operators: +, -, *, /, mod, pow, exp, sqrt, ln, log2, log10, hypot (%log already logs), along with comparisons, %if, %and, %or, %not and %range.
• User (%error msg) macro for aborting compilation.
• List reverse macro (%reverse (...)).
• Literal/atomic conversion macros: (%symbol lit), (%number lit), (%string lit), (%raw lit).
• Sorting macro (%sort (...)) which sorts alphanumerically on literals. Allow providing a :key to sort "by field": e.g. sort by title name (%sort :key (%lambda ((:title _ &&_)) %title) %posts)
• Extend the strftime-style (%date) to be able to read UNIX numeric timestamps and display relative to timezones. Add complementary strptime-style utility (%timestamp) to convert date-strings to timestamps (relative to a timezone).
• Pattern-matching (%match expr (pat1 ...) (pat2 ...)) macro. Pattern matching is already implemented for %define internally.
• The trailing keyword-matching operator. &&rest matches excess keyword. Extracting a value from a map (:a 1 :b 2 :c 3) is done with: (%match %h ((:b default &&_) %b)).
• %get macro: (%get b (:a 1 :b 2)) becomes 2; (%get 0 (a b c)) becomes a.
• (%yaml "..."), (%toml "...") and (%json "...") converts whichever config-lang definition into a seam %define-definition.
• (%do ...) which just expands to the ...; the identity function.
• Catch expansion errors: (%try (%do code-to-try) :error the-error (%do caught-error %the-error)).
• Implement (%strip ...) which evaluates to the ... without any of the leading whitespace.
• Implement splat operation: (%splat (a b c)) becomes a b c.
• (%define x %body) evaluates %body eagerly (at definition), while (%define (y) %body) only evaluates %body per call-site (%y).
• Namespace macro (%namespace ns (%include "file.sex")) will prefix all definitions in its body with ns/, e.g. %ns/defn. Allows for a customizable separator, e.g. (%namespace ns :separator "-" ...) will allow for writing %ns-defn. Otherwise, the macro leaves the content produced by the body completely unchanged.
• Command line -I include directory.
• First argument in a macro invocation should have its whitespace stripped.
• (%os/env ENV_VAR) environment variable macro.
• Lazy evaluation for user macros (like in ifdef): ~param parameters are expanded where they are used. Code can also be kept as data with (%quote ...), and expanded with (%eval ...).
• (%apply name x y z) macro which is equivalent to (%name x y z).
• (%lambda (x y) ...) macro which just evaluates to an secret symbol, e.g. __lambda0. used by applying %apply, e.g. (%apply (%lambda (a b) b a) x y) becomes y x
• (%string ...), (%join ...), (%map ...), (%filter ...) macros.
• Quasiquotation, (%quasi (a (%unquote %x) (%splice %xs))), and (%read "...").
• Inspecting and building nodes: %type, %list? (etc.), %attribute, %dict.
• List functions taking lambdas: %map, %filter, %fold, %find, %any, %all, %zip, %enumerate, %flatten, %group-by, (%sort :by ...).
• Walking trees: (%walk f tree) and (%select h2 tree).
• Tools for writing macros: %gensym, %defined and %macroexpand.
• (%concat ...) which is just (%join "" ...), or joins lists.
• Lazy lists, internally: ranges, slices, reversals and concatenations are made as needed, and %for never makes a whole list.
• Add options to %glob for sorting by type, date(s), name, etc.
• (%format "{}") macro with Rust's format syntax. e.g. (%format "Hello {}, age {age:0>2}" "Sam" :age 9)
• Add (%raw ...) macro which takes a string and leaves it unchanged in the final output.
• (%formatter/text ...) can take any seam (sexp) source code, for which it just embeds the expanded code (plain-text formatter).
• (%formatter/html ...) etc. which call the respective available formatters.
• Implement lexical scope by letting macros store a reference to the scope they were defined in.
• (%with (:name value ...) ...) dynamically overrides top-level definitions within its body, e.g. for passing page metadata through to a shared layout macro.
• (%embed "/path") macro, like %include, but just returns the file contents as a string.
• Variadic arguments via &rest syntax.
• Type-checking facilities for user macros.
• %list macro which expands from (%list %a %b %c) to ( %a %b %c ) but without calling %a as a macro with %b and %c as argument.
• %for-loop macro, iterating over %lists.
• %glob which returns a list of files/directories matching a glob.
• %markdown renders Markdown given to it as %raw html-string.
• Add keyword macro arguments.
• Caching or checking time-stamps as to not regenerate unmodified source files: (%write path :from (sources...) ...), and unchanged files are not rewritten.
• HTML object style="..." object should handle s-expressions well, (e.g. (p :style (:color red :border none) Hello World))
• JSON output (--json, %formatter/json), the reverse of %json.
• JavaScript output (--js, %formatter/js), written as s-expressions: (const f (=> (x) (* x x))).
• Add more supported formats (TOML, &c.).
• Allow for arbitrary embedding of code with their REPLs, that can be run by a LISP interpreter (or any other language), for example. (e.g. (%chez (+ 1 2)) executes (+ 1 2) with Chez-Scheme LISP, and places the result in the source (i.e. 3). Done with %exec: (%define (chez ~&code) (%exec scheme --quiet :stdin (%formatter/sexp %code))).