updated Chapter 10

Author: tzhenghao

21stCenturyC/Chapter10.md

@@ -4,14 +4,14 @@ f(double[]) {20.38, a_value, 9.8}); // OK
 
 	- Automatically allocated, neither malloc nor free needed.
 
-#include <math.h> // NAN
-#include <stdio.h>
-
-double sum(double in[]) {
-	double out = 0;
-	for (int i = 0;  !isnan(in[i]);  ++i) out += in[i];
-	return out;
-}
+-#include <math.h> // NAN
+-#include <stdio.h>
+-
+-double sum(double in[]) {
+-	double out = 0;
+-	for (int i = 0;  !isnan(in[i]);  ++i) out += in[i];
+-	return out;
+-}
 
 int main() {
 
@@ -24,3 +24,17 @@ sizeof(list) == sizeof(double*)
 
 
 ##Variadic Macros
+
+-#define forloop(i, loopmax, ...) for (int i=0; i < loopmax; ++i) \
+											{__VA_ARGS__}
+
+-int main() {
+
+	int sum = 0;
+	forloop(i, 10,
+			sum += i;
+			printf("sum to %i:\n", i, sum);
+	)
+}
+
+