add a tagging system to the website

content/programming/haku.tree

@@ -1,5 +1,7 @@
-%% title = "haku - writing a little programming language for fun"
+%% id = "b?01J4J5N6WZQ03VTB3TZ51J7QZK"
+title = "haku - writing a little programming language for fun"
 scripts = ["treehouse/vendor/codejar.js", "treehouse/components/literate-programming.js"]
+tags = ["all", "programming", "plt"]
 
 % id = "01J3K8A0D1774SFDPKDK5G9GPV"
 - I've had this idea on my mind as of late, of a little pure functional programming language that would run in your browser.
@@ -85,7 +87,7 @@ scripts = ["treehouse/vendor/codejar.js", "treehouse/components/literate-program
         | identifier | 9 | 21 | `s-expression` |
         | ) | 21 | 22 | `)` |
         | end of file | 22 | 22 | |
-    
+
     % id = "01J3K8A0D1GGQ292D4MQBCGHWC"
     - to lex the input into tokens, we'll need to know the input string (of course), and where we currently are in the string.
 
@@ -185,7 +187,7 @@ scripts = ["treehouse/vendor/codejar.js", "treehouse/components/literate-program
             }
         }
     }
-    
+
     printTokens(`()((()))`);
     ```
 
@@ -376,7 +378,7 @@ scripts = ["treehouse/vendor/codejar.js", "treehouse/components/literate-program
 
         lexer.advance(state);
         return "error";
-    };    
+    };
     ```
 
     % id = "01J3K8A0D1DKA8YCBCJVZXXGR4"
@@ -859,7 +861,7 @@ scripts = ["treehouse/vendor/codejar.js", "treehouse/components/literate-program
     ```
 
     that's... the same string.
-    
+
     % id = "01J3K8A0D1XP4FQB2HZR9GV5CJ"
     - let's try something more complicated, with comments and such.
 
@@ -887,10 +889,10 @@ scripts = ["treehouse/vendor/codejar.js", "treehouse/components/literate-program
 
         % id = "01J3K8A0D10DRSP49WF8YH5WSH"
         - of course this is hardly the _prettiest_ printer in the world.
-        
+
             % id = "01J3K8A0D1VCJ7TV6CN7M07N5J"
             - for one, it does not even preserve your comments.
-            
+
             % id = "01J3K8A0D1K3M9223YM96PS68B"
             - it does not add indentation either, it just blindly dumps a minimal S-expression into the console.
 
@@ -950,7 +952,7 @@ scripts = ["treehouse/vendor/codejar.js", "treehouse/components/literate-program
             % id = "01J3K8A0D1F4R8KPHETV9N08YP"
             - it's definitely not how I would write a parser nowadays.
             it's pretty similar, but the syntax tree structures are quite different - it doesn't use the [lazy parsing][branch:01J3K8A0D1FYBKJ6X2W17QAK3Z] trick I talked about before.
-            
+
                 % id = "01J3K8A0D178J6W49AFCE9HEQ6"
                 - I mean, it's only a trick I learned last year!
 
@@ -1008,7 +1010,7 @@ scripts = ["treehouse/vendor/codejar.js", "treehouse/components/literate-program
     ```
 
     for now we'll leave it empty.
-    
+
     % id = "01J3NVV2RX2T5K473GGY3K5VBX"
     - in the meantime, let's prepare a couple convenient little wrappers to run our code:
 
@@ -1092,7 +1094,7 @@ scripts = ["treehouse/vendor/codejar.js", "treehouse/components/literate-program
     {:program=haku}
     ```javascript
     export const builtins = {};
-    
+
     treewalk.eval = (state, node) => {
         switch (node.kind) {
             case "integer":
@@ -1862,7 +1864,7 @@ scripts = ["treehouse/vendor/codejar.js", "treehouse/components/literate-program
 
     {:program=haku}
     ```javascript
-    treewalk.eval = (state, node) => {    
+    treewalk.eval = (state, node) => {
         switch (node.kind) {
             case "integer":
                 let sourceString = state.input.substring(node.start, node.end);
@@ -2032,7 +2034,7 @@ scripts = ["treehouse/vendor/codejar.js", "treehouse/components/literate-program
                 throw new Error(`unhandled node kind: ${node.kind}`);
         }
     };
-    
+
     builtins.fn = (state, node) => {
         if (node.children.length != 3)
             throw new Error("an `fn` must have an argument list and a result expression");