c4

A Macro Language (usable like GNU m4) with template engine function and influence from m4, awk, ruby, razor, cpp (c preprocessor) and perl

while m4 and cpp are nice because they are simple. They are not enough to handle markdown.

awk is nice to proceed some database like information, which can split in fields and rowsets.

razor is a very nice and powerful template engine.

perl can handle regex / pcre in the best way.

ruby has some nice extention methods like .each which will be a benefit.

so mixin all these pros to a new one which will be able to handle nested (recursive) markup/markdown in hopefully a simple to read simple to extend syntax called c4.

A simple m4 Headings Numbering

The m4 Macro Definition:

divert(-1)

# The H2_COUNT macro is redefined every time the H2 macro is used:
define(`H2_COUNT', 0)

define(`H2',
	`define(`H2_COUNT', incr(H2_COUNT))<h2>H2_COUNT. $1</h2>')

divert(1)dnl

The m4 Macro calls:

H2(Erstes Kapitel)
H2(Zweites Kapitel)
H2(Schluss)

The m4 HTML output:

<h2>1. Erstes Kapitel</h2>
<h2>2. Zweites Kapitel</h2>
<h2>3. Schluss</h2>

---

A simple c4 Headings Numbering

The c4 Macro Definition:

h2($*):=> head2($*);

begin() {
  $h2_counter = 0;
}

head2(mark content) {
  <h2>@++$h2_counter. content</h2>
}

h2($*) matched the h2 macro and provides all inner data by $*. with the Brakets ( and ) a possible macro nesting is clear.

In this scenario it would be possible to rename head2 to h2 and no macro mapping in line 1 is necessary !

The c4 Macro calls:

h2(Erstes Kapitel)
h2(Zweites Kapitel)
h2(Schluss)

The c4 HTML output from Markdown:

<h2>1. Erstes Kapitel</h2>
<h2>2. Zweites Kapitel</h2>
<h2>3. Schluss</h2>

---

A simple c4 Headings Numbering from Markdown Source

The c4 Macro Definition:

match(/^## $*$/):=> head2($*);

begin() {
  $h2_counter = 0;
}

head2(mark content) {
  <h2>@++$h2_counter. content</h2>
}

with match(/.../) in a macro mapping it would be possible to catch text by regular expressions!

The Markdown:

## Erstes Kapitel
## Zweites Kapitel
## Schluss

The c4 HTML output from Markdown:

<h2>1. Erstes Kapitel</h2>
<h2>2. Zweites Kapitel</h2>
<h2>3. Schluss</h2>

---

A little more complex c4 Macro Definition:

which will reset the counter by each parent heading (h1):

#!/usr/bin/c4 -w
#h1h2.c4

 match(/^# $*$/):=> head1($*);
match(/^## $*$/):=> head2($*);

begin() {
  $h1_counter = 0;
  $h2_counter = 0;
}

head1(mark content) {
  $h2_counter = 0;  
  <h1>@++$h1_counter. content</h1>
}

head2(mark content) {
  <h2>@++$h1_counter.@++$h2_counter. content</h2>
}

The Markdown:

# Erstes Kapitel
## Erste Sektion
## Zweite Sektion
## Zusammenfassung

# Zweites Kapitel
## Erste Sektion
## Zweite Sektion

The c4 HTML output from Markdown:

<h1>1. Erstes Kapitel</h1>
<h2>1.1. Erste Sektion</h2>
<h2>1.2. Zweite Sektion</h2>
<h2>1.3. Zusammenfassung</h2>
<h1>2. Zweites Kapitel</h1>
<h2>2.1. Erste Sektion</h2>
<h2>2.2. Zweite Sektion</h2>

The cli for m4 -> html transformation

$ cat capter.md | c4 -m h1h2.c4 
<h1>1. Erstes Kapitel</h1>
<h2>1.1. Erste Sektion</h2>
<h2>1.2. Zweite Sektion</h2>
<h2>1.3. Zusammenfassung</h2>
<h1>2. Zweites Kapitel</h1>
<h2>2.1. Erste Sektion</h2>
<h2>2.2. Zweite Sektion</h2>

---

Take a look how a for-loop will be written in

C++ for:

for(int i=0; i<10; ++i)
{
  cout << i << "\n";
}

For-Loop in M4:

define(`for',
   `ifelse($#,0,``$0'',
   `ifelse(eval($2<=$3),1,
   `pushdef(`$1',$2)$5`'popdef(`$1')$0(`$1',eval($2+$4),$3,$4,`$5')')')')dnl

for(`x',`1',`5',`1',
   `for(`y',`1',x,`1',
      `*')
')

Native Loop in c4 via gotos and then a template which creates an ordinary for-loop template for c4:

{
  $i=0;
  label continue: if(expr !($i<10)) goto break 
  {
    printf "$i\n"
    ++$i
  } goto continue
  label break:
}  


template "for"(init; cond; inc)[continue, break]{algo}{
  expr init
  label continue: if(expr !cond) goto break 
  {
    {algo}
    expr inc
  } goto continue
  label break:
}  

for($i=0; $i<10; ++$i) {
  printf "$i\n"
}

But like in C++ this one above is a runtime loop! A Meta-Loop looks like this:

func<0> =>> func<0>(): false
func<n> =>> func<n>(): func<n-1>

func<int x>() => print "$x\n"

func<10>()

will be evaluated to ...

func<10>() ->  func<x:10> { print "10\n"; func<x:9>{ print "9\n"; func<x:8>{ print "8\n"; func<x:7>{