[Assorted-commits] SF.net SVN: assorted: [470] sandbox/trunk/src/c/mdarray.c

[<yan...@us...>]

Revision: 470
          http://assorted.svn.sourceforge.net/assorted/?rev=470&view=rev
Author:   yangzhang
Date:     2008-02-18 19:58:19 -0800 (Mon, 18 Feb 2008)

Log Message:
-----------
more md-array fun

Modified Paths:
--------------
    sandbox/trunk/src/c/mdarray.c

Modified: sandbox/trunk/src/c/mdarray.c
===================================================================
--- sandbox/trunk/src/c/mdarray.c	2008-02-19 00:13:41 UTC (rev 469)
+++ sandbox/trunk/src/c/mdarray.c	2008-02-19 03:58:19 UTC (rev 470)
@@ -1,18 +1,48 @@
-int xss[3][5];
+#include <stdio.h>
 
+enum { outer = 3, inner = 5 };
+
+// This is an Array[outer, Array[inner, Int]]
+int xss[outer][inner];
+
 int
 main()
 {
-  // Don't work.
+  // These don't work.
   // int **yss = xss;
-  // int *yss = xss;
-  // int **yss = xss;
-  // int **yss = &&xss[0];
-  int (*yss)[5] = xss;
+  // int **yss = &xss[0];
+  // int **yss = &&xss[0][0];
 
-  int sum = 0;
-  for (int i = 0; i < 3; i++)
-    for (int j = 0; j < 5; j++)
-      sum += yss[i][j];
-  return sum;
+  // This is a Pointer[Array[inner, Int]].
+  int (*yss)[inner] = xss;
+
+  {
+    // This is safe.
+    printf("method 0: indexing\n");
+    int sum = 0;
+    for (int i = 0; i < outer; i++) {
+      printf("outer visiting: %p\n", &yss[i]);
+      for (int j = 0; j < inner; j++) {
+        printf("inner visiting: %p\n", &yss[i][j]);
+        sum += yss[i][j];
+      }
+    }
+    printf("sum = %d\n", sum);
+  }
+
+  {
+    // This method is wrong, running off into segfault land.
+    printf("method 1: pointers\n");
+    int sum = 0;
+    for (int (*p)[5] = yss; p < yss + outer; p++) {
+      printf("outer visiting: %p\n", p);
+      for (int *q = *p; q < q + inner; q++) {
+        printf("inner visiting: %p\n", q);
+        sum += *q;
+      }
+    }
+    printf("sum = %d\n", sum);
+  }
+
+  return 0;
 }


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