support catting subpatterns, fixes #87

packages/core/pattern.mjs

@@ -837,7 +837,10 @@ export function stack(...pats) {
 export function slowcat(...pats) {
   // Concatenation: combines a list of patterns, switching between them
   // successively, one per cycle.
-  pats = pats.map(reify);
+
+  // Array test here is to avoid infinite recursions..
+  pats = pats.map(pat => Array.isArray(pat) ? sequence(...pat) : reify(pat));
+
   const query = function (state) {
     const span = state.span;
     const pat_n = mod(span.begin.sam(), pats.length);

packages/core/test/pattern.test.mjs

@@ -413,6 +413,12 @@ describe('Pattern', function () {
         ['c'],
       );
     });
+    it ('Can cat subpatterns', () => {
+      sameFirst(
+        slowcat('a', ['b','c']).fast(4),
+        sequence('a', ['b', 'c']).fast(2)
+      )
+    })
   });
   describe('rev()', function () {
     it('Can reverse things', function () {