added SetBasicCallback example

git-svn-id: svn://136.177.114.72/svn_GW/IPhreeqc/trunk@8010 1feff8c3-07ed-0310-ac33-dd36852eb9cd

doc/examples/SetBasicCallback.c

@@ -0,0 +1,82 @@
+#include <stdlib.h>
+#include <IPhreeqc.h>
+
+#define TRUE  1
+
+const char input[] =
+  "SOLUTION 1-2                                            \n"
+  "END                                                     \n"
+  "EQUILIBRIUM_PHASES 1                                    \n"
+  "   CO2(g) -1.5 10                                       \n"
+  "EQUILIBRIUM_PHASES 2                                    \n"
+  "   Calcite 0   10                                       \n"
+  "SELECTED_OUTPUT                                         \n"
+  "   -reset false                                         \n"
+  "USER_PUNCH                                              \n"
+  "   -Heading  pH  SR(calcite)   Year                     \n"
+  "   30 PUNCH -LA(\"H+\"), SR(\"calcite\")                \n"
+  "   40 PUNCH CALLBACK(cell_no, -LA(\"H+\"), \"Year\")    \n"
+  "END                                                     \n";
+
+struct MyData
+{
+  double year;
+};
+
+double MyCallback(double x1, double x2, const char * str1, void *mydata)
+{
+  /*
+    Use of a callback is optional.
+    
+    The callback provides a way to obtain data from a Basic program
+    through the variables x1, x2, and str1, and send data to a 
+    Basic program through the return value of the callback.
+    
+    The void pointer mydata can be used to obtain data from the
+    calling program; in this example, it points to a structure.
+    
+    The callback function is called whenever CALLBACK(x1, x2, str$)  
+    is used in a Basic program (usually USER_PUNCH).
+  */
+  if (strcmp(str1, "Year") == 0)
+  {
+    fprintf(stderr, "\nCallback for cell %d: pH %8.2f\n", (int) x1, x2);
+    return ((struct MyData *) mydata)->year;
+  }
+  return -1;
+}
+
+int main(void)
+{
+  struct MyData mydata;
+  int id;
+  
+  mydata.year = 2012.0;
+  
+  id = CreateIPhreeqc();
+  if (id < 0) {
+    return EXIT_FAILURE;
+  }
+
+  if (LoadDatabase(id, "phreeqc.dat") != 0) {
+    OutputErrorString(id);
+    return EXIT_FAILURE;
+  }
+  
+  if (SetSelectedOutputFileOn(id, TRUE) != IPQ_OK) {
+    OutputErrorString(id);
+    return EXIT_FAILURE;
+  }
+  
+  if (SetBasicCallback(id, MyCallback, &mydata) != IPQ_OK) {
+    OutputErrorString(id);
+    return EXIT_FAILURE;
+  }
+
+  if (RunString(id, input) != 0) {
+    OutputErrorString(id);
+    return EXIT_FAILURE;
+  }
+  
+  return EXIT_SUCCESS;
+}