added help command

k&r/04-funcs-and-prog-struct/04-calc.c

@@ -17,7 +17,10 @@
 #define PROMPT_F     ">> "
 #define POP_PRINT_F  "pop -> %.8g\n"
 #define PEEK_PRINT_F "peek -> %.8g\n"
-#define EMPTY_F      "empty\n"
+#define INITIAL_PROMPT_F \
+    "A simple calculator using polish notation.\n" \
+    "Type 'help' for a list of available commands\n" \
+    PROMPT_F
 
 /* ------ GLOBAL VALUE STACK */
 #define MAXVAL 100 /* maximum depth of val stack */
@@ -82,44 +85,46 @@ double val[MAXVAL];
 /* renaming macro */
 #define CALL(TOKEN, F, APPLY, ...) APPLY(F, ##__VA_ARGS__)
 
+void help(void);
 
 #define COMMANDS \
-    X(print, CALL, print_peek, COMMAND) \
-    X(dup, COMMAND) \
-    X(swap, COMMAND) \
-    X(clear, COMMAND) 
+    X(print, "print top of stack", CALL, print_peek, COMMAND) \
+    X(dup, "duplicate top of stack", COMMAND) \
+    X(swap, "swap top two elements of stack", COMMAND) \
+    X(clear, "clear stack", COMMAND) \
+    X(help, "print all available commands", COMMAND)
 
 #define OPERATORS \
-    X(+, COMM_OP) \
-    X(*, COMM_OP) \
-    X(-, NONC_OP, double) \
-    X(/, NONC_OP, double, NONZ_SND_OP) \
-    X(%, NONC_OP, int, NONZ_SND_OP) \
-    X(>, NONC_OP, double) \
-    X(<, NONC_OP, double) \
-    X(<=, NONC_OP, double) \
-    X(>=, NONC_OP, double)
+    X(+, "add operands", COMM_OP) \
+    X(*, "multiply operands", COMM_OP) \
+    X(-, "substact operands", NONC_OP, double) \
+    X(/, "divide operands", NONC_OP, double, NONZ_SND_OP) \
+    X(%, "modulo operands", NONC_OP, int, NONZ_SND_OP) \
+    X(>, "greater than", NONC_OP, double) \
+    X(<, "less than", NONC_OP, double) \
+    X(<=, "less than or equal", NONC_OP, double) \
+    X(>=, "greater than or equal", NONC_OP, double)
 
 #define MATH_H_BINDINGS \
-    X(sin, UNARY_FUN) \
-    X(cos, UNARY_FUN) \
-    X(tan, UNARY_FUN) \
-    X(acos, UNARY_T_FUN, double, IN_RANGE(-1, 1)) \
-    X(asin, UNARY_T_FUN, double, IN_RANGE(-1, 1)) \
-    X(atan, UNARY_FUN) \
-    X(exp, UNARY_FUN) \
-    X(log, UNARY_T_FUN, double, NON_NEG) \
-    X(log10, UNARY_T_FUN, double, NON_NEG) \
-    X(log2, UNARY_T_FUN, double, NON_NEG) \
-    X(pow, NONC_FUN, double) \
-    X(sqrt, UNARY_T_FUN, double, NON_NEG) \
-    X(ceil, UNARY_FUN) \
-    X(floor, UNARY_FUN) \
-    X(round, UNARY_FUN) \
-    X(abs, CALL, fabs, UNARY_FUN) \
-    X(max, CALL, fmax, COMM_FUN) \
-    X(min, CALL, fmin, COMM_FUN) \
-    X(pi, CALL, M_PI, VALUE)
+    X(sin, "sine", UNARY_FUN) \
+    X(cos, "cosine", UNARY_FUN) \
+    X(tan, "tangent", UNARY_FUN) \
+    X(acos, "arc cosine", UNARY_T_FUN, double, IN_RANGE(-1, 1)) \
+    X(asin, "arc sine", UNARY_T_FUN, double, IN_RANGE(-1, 1)) \
+    X(atan, "arc tangent", UNARY_FUN) \
+    X(exp, "exponentional function", UNARY_FUN) \
+    X(log, "natural logarithm", UNARY_T_FUN, double, NON_NEG) \
+    X(log10, "logarithm of base 10", UNARY_T_FUN, double, NON_NEG) \
+    X(log2, "logarithm of base 2", UNARY_T_FUN, double, NON_NEG) \
+    X(pow, "power function", NONC_FUN, double) \
+    X(sqrt, "square root", UNARY_T_FUN, double, NON_NEG) \
+    X(ceil, "round up value", UNARY_FUN) \
+    X(floor, "round down value", UNARY_FUN) \
+    X(round, "round to nearest", UNARY_FUN) \
+    X(abs, "absolute value", CALL, fabs, UNARY_FUN) \
+    X(max, "maximum value", CALL, fmax, COMM_FUN) \
+    X(min, "minimum value", CALL, fmin, COMM_FUN) \
+    X(pi, "value of pi", CALL, M_PI, VALUE)
     
 
 #define TOKENS \
@@ -127,7 +132,7 @@ double val[MAXVAL];
     OPERATORS \
     MATH_H_BINDINGS
 
-/* --------- COMMAND DEFINITIONS */ 
+/* --------- MAIN PROGRAM */ 
 
 #define MAXTOKEN 100
 int gettoken(char *token, int max_t);
@@ -140,13 +145,14 @@ int main()
     double x;
     int t_len;
     
-    printf(PROMPT_F);
+    printf(INITIAL_PROMPT_F);
     while (t_len = gettoken(token, MAXTOKEN)) {
         if (t_len < 0) { /* newline token */
-            length() ? printf(POP_PRINT_F,  pop()) :  printf(EMPTY_F);
+            if (length())
+                printf(POP_PRINT_F,  pop());
             printf(PROMPT_F);
         } else
-    #define X(F, APPLY, ...) \
+    #define X(F, DESC, APPLY, ...) \
         if (t_len == sizeof(#F) / sizeof(char) - 1 && !strcmp(#F, token)) \
             APPLY(F, ##__VA_ARGS__); \
         else
@@ -165,6 +171,18 @@ int main()
     return 0;
 }
 
+
+#define COMMAND_W "10"
+#define NEWLINE_DESC "pop top of stack and print it"
+/* help: prints all available calculator functions */
+void help(void)
+{
+    printf("%-" COMMAND_W "s" NEWLINE_DESC "\n", "ENTER");
+#define X(F, DESC, ...) printf("%-" COMMAND_W "s" DESC "\n", #F);
+    TOKENS
+#undef X
+}
+
 /* -------- PARSING FUNCTIONS */
 #include <ctype.h>