parsing pattern matching

src/ast.ts

@@ -127,7 +127,7 @@ export function prettyPrint(ast: AST, indent = 0): string {
 
     switch (ast.kind) {
         case 'literal':
-            return `${i}${ast.value.value}`;
+            return `${i}${ast.value}`;
 
         case 'variable':
             return `${i}${ast.name}`;
@@ -154,17 +154,56 @@ export function prettyPrint(ast: AST, indent = 0): string {
             return `${i}{${fields}}`;
 
         case 'lambda':
-            const params = ast.params.join(', ')
+            const params = ast.params.join(', ');
             return `${i}(${params}) => ${prettyPrint(ast.body)}`
 
         case 'record-access':
-            return `${i}${prettyPrint(ast.record)}.${ast.field}`
+            return `${i}${prettyPrint(ast.record)}.${ast.field}`;
 
         case 'record-update':
             const updates = Object.entries(ast.updates).map(([k, v]) => `${k} = ${prettyPrint(v, 0)}`).join(', ');
             return `${i}${prettyPrint(ast.record)} { ${updates} }`
 
+        case 'match':
+            const expr = prettyPrint(ast.expr, 0);
+            const cases = ast.cases
+                .map(c => `  | ${prettyPrintPattern(c.pattern)} -> ${prettyPrint(c.result, 0)}`)
+                .join('\n');
+            return `${i}match ${expr}\n${cases}`;
+
+
         default:
             return `${i}${ast.kind}`
     }
 }
+
+function prettyPrintPattern(pattern: Pattern): string {
+    switch (pattern.kind) {
+        case 'wildcard':
+            return '_';
+
+        case 'var':
+            return pattern.name;
+
+        case 'literal':
+            return JSON.stringify(pattern.value);
+
+        case 'constructor':
+            if (pattern.args.length === 0) {
+                return pattern.name;
+            }
+            const args = pattern.args.map(prettyPrintPattern).join(' ');
+            return `(${pattern.name} ${args})`;
+
+        case 'list':
+            const elems = pattern.elements.map(prettyPrintPattern).join(', ');
+            return `[${elems}]`;
+
+        case 'record':
+            const fields = Object.entries(pattern.fields)
+                .map(([k, p]) => `${k} = ${prettyPrintPattern(p)}`)
+                .join(', ');
+
+            return `{${fields}}`;
+    }
+}