redefined stack manipulation functions as macros

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

@@ -3,13 +3,14 @@
 #include <string.h>
 #include <math.h>
 
-
+/* --------- ERROR MESSAGES */
 #define printerr(format, ...) printf("error: " format "\n", ##__VA_ARGS__)
-int stack_len(void);
+#define ZERODIV_ERR "zero divisor"
-void push(double x);
+#define DOMAIN_ERR "operand not in domain [%d, %d]"
-double pop(void);
+#define NEG_ERR "negative operand %g"
-double peek(void);
+#define FULL_STACK_ERR  "stack full, can't push %g"
-void clear(void);
+#define EMPTY_STACK_ERR "stack empty" 
+#define SHORT_STACK_ERR "not enough elements on stack"
 
 /* --------- PROMPT FORMATS */
 #define PROMPT_F     ">> "
@@ -17,52 +18,72 @@ void clear(void);
 #define PEEK_PRINT_F "peek -> %.8g\n"
 #define EMPTY_F      "empty\n"
 
-/* --------- ERROR MESSAGES */
+/* ------ GLOBAL VALUE STACK */
-#define ZERODIV_ERR "zero divisor"
+#define MAXVAL 100 /* maximum depth of val stack */
-#define DOMAIN_ERR "operand not in domain [%d, %d]"
+
-#define NEG_ERR "negative operand %g"
+int sp = 0;
-#define FULL_STACK_ERR  "stack full, can't push %g"
+double val[MAXVAL];
-#define EMPTY_STACK_ERR "stack empty" 
+
+#define length() sp
+/* push: push f onto value stack */
+#define push(x) ((sp < MAXVAL) ? val[sp++] = (x) : printerr(FULL_STACK_ERR, ((double) (x))))
+/* pop: pop and return top value from stack */
+#define pop() (sp ? val[--sp] : (printerr(EMPTY_STACK_ERR), 0))
+/* peek: return top value from stack, leave stack unchanged */
+#define peek() (sp ? val[sp-1] : (printerr(EMPTY_STACK_ERR), 0))
+/* clear: clear stack */
+#define clear() (sp = 0)
+/* print_peek: print top element, leave stack unchanged */
+#define print_peek() printf(PEEK_PRINT_F, peek())
+/* dup: duplicate top element */
+#define dup() push(peek())
+/* swap: swap top two elements */
+#define swap() \
+   do { if (sp < 2) printerr(SHORT_STACK_ERR); else { \
+            double tmp = peek(); \
+            val[sp-1] = val[sp-2], val[sp-2] = tmp; \
+        } \
+   } while (0) 
 
 /* --------- CALCULATOR FUNCTION TYPES */
-/* renaming macro */
-#define CALL(TOKEN, F, APPLY, ...) APPLY(F, ##__VA_ARGS__)
 
+/* the following macros allow us to call native c constructs in a declarative style */
 /* value */
 #define VALUE(ID) push(ID)
-
 /* command */
 #define COMMAND(CMD) CMD()
-
 /* commutative operator */
 #define COMM_OP(OP) push(pop() OP pop()) 
 /* non-commutative operator */
 #define NONC_OP(OP, T, ...) \
     do { T op = pop(); __VA_ARGS__ push(((T) pop()) OP op); } while (0)
-/* nonzero second operand */
-#define NONZ_SND_OP if (!op) printerr(ZERODIV_ERR); else
-
 /* unary function */
 #define UNARY_FUN(F) push(F(pop()))
 /* unary function with tests */
-#define UNARY_T_FUN(F, T, ...) do { double op = pop(); __VA_ARGS__ push(F(op)); } while (0)
+#define UNARY_T_FUN(F, T, ...) \
-/* operator in range */
+    do { double op = pop(); __VA_ARGS__ push(F(op)); } while (0)
-#define IN_RANGE(A, B) if (op < A || op > B) printerr(DOMAIN_ERR, A, B); else
-/* operator > 0 */
-#define NON_NEG if (op < 0) printerr(NEG_ERR, op); else
-
 /* commutative function */
 #define COMM_FUN(F) push(F(pop(), pop()))
 /* non-commutative function */
 #define NONC_FUN(F, T, ...) \
     do { T op = pop(); __VA_ARGS__ push(F(pop(), op)); } while (0)
 
+/* nonzero operand */
+#define NONZ_SND_OP if (!op) printerr(ZERODIV_ERR); else
+/* operator in range */
+#define IN_RANGE(A, B) if (op < A || op > B) printerr(DOMAIN_ERR, A, B); else
+/* non-negative operand  */
+#define NON_NEG if (op < 0) printerr(NEG_ERR, op); else
 
 
 /* --------- CALCULATOR FUNCTIONS */
 
+/* renaming macro */
+#define CALL(TOKEN, F, APPLY, ...) APPLY(F, ##__VA_ARGS__)
+
+
 #define COMMANDS \
-    X(print, COMMAND) \
+    X(print, CALL, print_peek, COMMAND) \
     X(dup, COMMAND) \
     X(swap, COMMAND) \
     X(clear, COMMAND) 
@@ -107,12 +128,6 @@ void clear(void);
 
 /* --------- COMMAND DEFINITIONS */ 
 
-#define print() printf(PEEK_PRINT_F, peek())
-#define dup() push(peek())
-#define swap() \
-    do { double fst, snd; snd = pop(), fst = pop(); push(snd), push(fst); } while (0)
-
-
 #define MAXTOKEN 100
 int gettoken(char *token, int max_t);
 
@@ -126,7 +141,7 @@ int main()
     printf(PROMPT_F);
     while (t_len = gettoken(token, MAXTOKEN)) {
         if (t_len < 0) { /* newline token */
-            if (stack_len())
+            if (length())
                 printf(POP_PRINT_F,  pop());
             else
                 printf(EMPTY_F);
@@ -140,9 +155,9 @@ int main()
     #undef X
         push(atof(token));
     }
-    if (!stack_len())
+    if (!length())
         putchar('\n');
-    while (stack_len())
+    while (length())
         printf(POP_PRINT_F, pop());
 
     return 0;
@@ -176,47 +191,3 @@ int gettoken(char *token, int t_max)
     token[i] = '\0';
     return i;
 }
-
-/* ------ GLOBAL STACK */
-#define MAXVAL 100 /* maximum depth of val stack */
-
-int sp = 0;
-double val[MAXVAL];
-
-int stack_len()
-{
-    return sp;
-}
-
-
-/* push: push f onto value stack */
-void push(double f)
-{
-    if (sp < MAXVAL)
-        val[sp++] = f;
-    else
-        printerr(FULL_STACK_ERR, f);
-}
-
-/* pop: pop and return top value from stack */
-double pop(void)
-{
-    if (sp)
-        return val[--sp];
-    printerr(EMPTY_STACK_ERR);
-    return 0;
-}
-
-/* peek: return top value from stack, leave stack unchanged */
-double peek(void)
-{
-    if (sp)
-        return val[sp-1];
-    printerr(EMPTY_STACK_ERR);
-    return 0.0;
-}
-
-void clear(void)
-{
-    sp = 0;
-}