Add a new module to analyse categories

Author: sungshik

rascal-textmate-core/src/main/rascal/lang/rascal/grammar/analyze/Categories.rsc

@@ -0,0 +1,47 @@
+module lang::rascal::grammar::analyze::Categories
+
+import Grammar;
+import ParseTree;
+
+import lang::rascal::grammar::Util;
+
+@synopsis{
+    Special value to indicate that a production has no category
+}
+
+public str NO_CATEGORY = "";
+
+@synopsis{
+    Gets a set of categories such that, for each category, there exists a string
+    with that category produced by production `p`, as part of a string produced
+    by a start production of grammar `g`
+}
+
+set[str] getCategories(Grammar g, Production p)
+    = getCategoriesByProduction(g)[p];
+
+@memo
+private map[Production, set[str]] getCategoriesByProduction(Grammar g) {
+    map[Production, set[str]] ret = (p: {} | /p: prod(_, _, _) := g);
+
+    void doGet(Production p, set[str] parentCategories) {
+        set[str] categories = {c | /\tag("category"(str c)) := p};
+
+        set[str] old = ret[p];
+        set[str] new = _ <- categories ? categories : old + parentCategories;
+        ret[p] = new;
+
+        // If the new categories of `p` are different from the old ones, then
+        // propagate these changes to the children of `p`
+        for (old != new, /Symbol s := p.symbols, child <- lookup(g, delabel(s))) {
+            doGet(child, new);
+        }
+    }
+
+    // Propagate categories from the roots of the grammar
+    for (root: prod(\start(_), _, _) <- ret) {
+        doGet(root, {NO_CATEGORY});
+    }
+
+    return ret;
+}