1 files changed, 13 insertions, 8 deletions

diff --git a/math.c b/math.c
index 75b4cdeb5..3b459f62e 100644
--- a/math.c
+++ b/math.c
@@ -7,7 +7,10 @@
 
 /* Tiny RPN calculator, because "expr" didn't give me bitwise operations. */
 
-static const char math_usage[] = "math expression ...";
+static const char math_usage[] = "math expression ...\n\n"
+                "This is a Tiny RPN calculator that understands the\n"
+                "following operations: +, -, /, *, and, or, not, eor.\n"
+                "i.e. 'math 2 2 add' -> 4, and 'math 8 8 \\* 2 2 + /' -> 16\n";
 
 static double stack[100];
 static unsigned int pointer;
@@ -85,14 +88,14 @@ struct op {
 };
 
 static const struct op operators[] = {
-        {"add", add},
+        {"+", add},
+        {"-", sub},
+        {"*", mul},
+        {"/", divide},
         {"and", and},
-        {"div", divide},
-        {"eor", eor},
-        {"mul", mul},
-        {"not", not},
         {"or", or},
-        {"sub", sub},
+        {"not", not},
+        {"eor", eor},
         {0, 0}
 };
 
@@ -127,11 +130,13 @@ static void stack_machine(const char *argument)
 
 int math_main(int argc, char **argv)
 {
+        if (argc < 1 || *argv[1]=='-')
+                usage(math_usage);
         while (argc >= 2) {
                 stack_machine(argv[1]);
                 argv++;
                 argc--;
         }
         stack_machine(0);
-        return 0;
+        exit( TRUE);
 }