Added yylex_destroy

exercises/02/vslc/src/vslc.c

@@ -0,0 +1,57 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <getopt.h>
+#include <vslc.h>
+
+
+/* Global state */
+
+node_t *root;               // Syntax tree
+
+
+/* Command line option parsing for the main function */
+static void options ( int argc, char **argv );
+bool
+    print_full_tree = false;
+
+
+/* Entry point */
+int
+main ( int argc, char **argv )
+{
+    options ( argc, argv );
+
+    yyparse();  // Generated from grammar/bison, constructs syntax tree
+    
+    yylex_destroy(); // Free heap used by flex
+
+    if ( print_full_tree )
+        print_syntax_tree();
+
+    destroy_syntax_tree();     // In tree.c
+}
+
+
+static const char *usage =
+"Command line options\n"
+"\t-h\tOutput this text and halt\n"
+"\t-t\tOutput the full syntax tree\n";
+
+
+static void
+options ( int argc, char **argv )
+{
+    int o;
+    while ( (o=getopt(argc,argv,"ht")) != -1 )
+    {
+        switch ( o )
+        {
+            case 'h':
+                printf ( "%s:\n%s", argv[0], usage );
+                exit ( EXIT_FAILURE );
+                break;
+            case 't':   print_full_tree = true;             break;
+        }
+    }
+}
+