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@ -122,7 +122,7 @@ I have no idea if this is the best solution, but so far it proved to work:
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env = last()
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if (env == "none") {
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# If no block, print a paragraph
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print "<p>" replaceEmAndStrong($0) "</p>"
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print "<p>" $0 "</p>"
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} else if (env == "blockquote") {
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print $0
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}
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@ -151,3 +151,56 @@ Nonetheless the code can still be consulted on [github](https://github.com/Siwon
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For now we have seen a way to parse blocks, but markdown also handles strong, emphasis and links. However, these tags can appear anywhere in a line.
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Hence we need to be able to parse these lines apart from the block itself : indeed a header can container a strong and a link.
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A very useful function in awk is `match` : it literally is a regex engine, looking for a pattern in a string.
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Whenever the pattern is found, two global variables are filled :
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- RSTART : the index of the first character matching the *group*
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- RLENGTH: the length of the matched *group*
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For the following, `line` represents the line processed by the function, as the following `while` loops are actually part of a single function.
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This way `match(line, /\*([^*]+)\*/)` matches a string surrounded by two `*`, corresponding to an emphasis text.
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The `*` are espaced are thez are special characters, and the *group* is inside the parenthesis.
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To matche several instances of emphasis text within a line, a simple `while` will do the trick.
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We now only have to insert html tags `<em>` are the right space around the matched text, and we are good to go.
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We can save the global variables `RSTART` and `RLENGTH` for further use, in case they were to be change. Using them we also can extract the
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matched substrings and reconstruct the actual html string :
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while (match(line, /\*([^*]+)\*/)) {
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start = RSTART
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end = RSTART + RLENGTH - 1
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# Build the result: before match, <em>, content, </em>, after match
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line = substr(line, 1, start-1) "<em>" substr(line, start+1, RLENGTH-2) "</em>" substr(line, end+1)
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}
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We now can repeat the pattern for all inline fonctionnalities, e.g. strong and code.
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The case of url is a bit more deep as we need to match two groups : the actual text and the url itself.
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No real issue here, the naïve way is to match thd whole, and looking for both the link and the url within the matched whole.
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This way `match(line, /\[([^\]]+)\]\([^\)]+\)/)` matches a text between `[]` followed by a text between `()` : the markdown representation of links.
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As above, we store the `start` and `end` and also the whole match :
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start = RSTART
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end = RSTART + RLENGTH - 1
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matched = substr($0, RSTART, RLENGTH)
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It is possible to apply the match fonction on this `matched` string, and extract, first, the text in `[]`, and last the text in `()`
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if (match(matched, /\[([^\]]+)\]/)) {
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matched_link = substr(matched, RSTART+1, RLENGTH-2)
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}
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if (match(matched, /\([^\)]+\)/)) {
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matched_url = substr(matched, RSTART+1, RLENGTH-2)
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}
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As the link text and the url are stored, using the variables `start` and `end`, it is easy to reconstruct the html line :
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line = substr(line, 1, start-1) "<a href=\"" matched_url "\">" matched_link "</a>" substr(line, end+1)
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The inline parsing function is now complete, all we have to do it apply is systematically on the text within html tags and this finished the markdown parser.
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This, of course, is the first brick of a static site generator, maybe the most complexe one.
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We shall see up next how to orchestrate this parser to make is a actual site generator.
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@ -124,7 +124,7 @@ function last() {
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env = last()
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if (env == "none") {
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# If no block, print a paragraph
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print "<p>" replaceEmAndStrong($0) "</p>"
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print "<p>" $0 "</p>"
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} else if (env == "blockquote") {
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print $0
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}
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@ -151,6 +151,53 @@ function last() {
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<h2>Parsing in-line fonctionnalities</h2>
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<p>For now we have seen a way to parse blocks, but markdown also handles strong, emphasis and links. However, these tags can appear anywhere in a line.</p>
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<p>Hence we need to be able to parse these lines apart from the block itself : indeed a header can container a strong and a link.</p>
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<p>A very useful function in awk is `match` : it literally is a regex engine, looking for a pattern in a string.</p>
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<p>Whenever the pattern is found, two global variables are filled :</p>
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<ul>
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<li>RSTART : the index of the first character matching the *group*</li>
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<li>RLENGTH: the length of the matched *group*</li>
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</ul>
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<p>For the following, `line` represents the line processed by the function, as the following `while` loops are actually part of a single function.</p>
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<p>This way `match(line, /\<em>([^</em>]+)\<em>/)` matches a string surrounded by two `</em>`, corresponding to an emphasis text.</p>
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<p>The `<em>` are espaced are thez are special characters, and the </em>group* is inside the parenthesis.</p>
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<p>To matche several instances of emphasis text within a line, a simple `while` will do the trick.</p>
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<p>We now only have to insert html tags `<em>` are the right space around the matched text, and we are good to go.</p>
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<p>We can save the global variables `RSTART` and `RLENGTH` for further use, in case they were to be change. Using them we also can extract the </p>
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<p>matched substrings and reconstruct the actual html string :</p>
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<pre><code>while (match(line, /\*([^*]+)\*/)) {
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start = RSTART
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end = RSTART + RLENGTH - 1
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# Build the result: before match, <em>, content, </em>, after match
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line = substr(line, 1, start-1) "<em>" substr(line, start+1, RLENGTH-2) "</em>" substr(line, end+1)
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}
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</code>
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</pre>
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<p>The case of url is a bit more deep as we need to match two groups : the actual text and the url itself.</p>
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<p>No real issue here, the naïve way is to match thd whole, and looking for both the link and the url within the matched whole.</p>
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<p>This way `match(line, /\[([^\]]+)\]\([^\)]+\)/)` matches a text between `[]` followed by a text between `()` : the markdown representation of links.</p>
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<p>As above, we store the `start` and `end` and also the whole match :</p>
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<p> </p>
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<pre><code>start = RSTART
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end = RSTART + RLENGTH - 1
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matched = substr($0, RSTART, RLENGTH)
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</code>
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</pre>
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<p>It is possible to apply the match fonction on this `matched` string, and extract, first, the text in `[]`, and last the text in `()`</p>
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<pre><code>if (match(matched, /\[([^\]]+)\]/)) {
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matched_link = substr(matched, RSTART+1, RLENGTH-2)
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}
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if (match(matched, /\([^\)]+\)/)) {
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matched_url = substr(matched, RSTART+1, RLENGTH-2)
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}
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</code>
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</pre>
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<p>As the link text and the url are stored, using the variables `start` and `end`, it is easy to reconstruct the html line :</p>
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<pre><code>line = substr(line, 1, start-1) "<a href="" matched_url "">" matched_link "</a>" substr(line, end+1)
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</code>
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</pre>
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<p>The inline parsing function is now complete, all we have to do it apply is systematically on the text within html tags and this finished the markdown parser.</p>
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<p>This, of course, is the first brick of a static site generator, maybe the most complexe one. </p>
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<p>We shall see up next how to orchestrate this parser to make is a actual site generator.</p>
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</article>
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</body>
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