bistromathic: check completion

* examples/c/bistromathic/bistromathic.test: here.
* examples/c/bistromathic/parse.y (expected_tokens): Fix a memory
leak.

examples/c/bistromathic/bistromathic.test

@@ -79,3 +79,18 @@ cat >input <<EOF
 EOF
 run 0 '> 1 / 0
 > err: 1.1-5: error: division by zero'
+
+
+## ------------ ##
+## Completion.  ##
+## ------------ ##
+
+sed -e 's/\\t/	/g' >input <<EOF
+( 1 + \t\t
+EOF
+run 0 '> ( 1 + 
+(                        cos                      ln
+-                        double precision number  sin
+atan                     exp                      sqrt
+> ( 1 + 
+> err: 1.7: syntax error: expected - or ( or double precision number or function or variable before end of file'

examples/c/bistromathic/parse.y

@@ -356,7 +356,9 @@ expected_tokens (const char *input,
   // Then query for the accepted tokens at this point.
   yyparse_context_t yyctx
     = {ps->yyssp, YYEMPTY, &lloc, ps->yyesa, &ps->yyes, &ps->yyes_capacity};
-  return yyexpected_tokens (&yyctx, tokens, ntokens);
+  int res = yyexpected_tokens (&yyctx, tokens, ntokens);
+  yypstate_delete (ps);
+  return res;
 }
 
 /* Attempt to complete on the contents of TEXT.  START and END bound the