New examples for compile_ex and link_ex.

[ginac.git] / doc / examples / compile2.cpp

diff --git a/doc/examples/compile2.cpp b/doc/examples/compile2.cpp
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+++ b/doc/examples/compile2.cpp
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+#include <iostream>
+using namespace std;
+#include <ginac/ginac.h>
+using namespace GiNaC;
+// Yes, we are using CUBA (should be installed on the system!)
+#include <cuba.h>
+
+/*
+ * Demonstrates the use of compile_ex with the CUBA library.
+ *
+ * The user can enter an expression on the command line. This expression is
+ * compiled via compile_ex and integrated over the region 0 <= x,y <= 1 with
+ * the help of the CUBA library (http://www.feynarts.de/cuba).
+ *
+ */
+
+int main()
+{
+       // Let the user enter a expression
+       symbol x("x"), y("y");
+       string s;
+       cout << "Enter an expression containing 'x' and/or 'y': ";
+       cin >> s;
+       // Expression now in expr
+       ex expr(s, lst(x,y));
+ 
+       cout << "start integration of " << expr << " ..." << endl;
+
+       // Some definitions for VEGAS 
+       #define NDIM 2
+       #define NCOMP 1
+       #define EPSREL 1e-3
+       #define EPSABS 1e-12
+       #define VERBOSE 0
+       #define MINEVAL 0
+       #define MAXEVAL 50000
+       #define NSTART 1000
+       #define NINCREASE 500
+
+       // Some variables for VEGAS
+       int comp, nregions, neval, fail;
+       double integral[NCOMP], error[NCOMP], prob[NCOMP];
+
+       // Our function pointer that points to the compiled ex
+       FUNCP_CUBA fp;
+       compile_ex(lst(expr), lst(x,y), fp);
+
+       // Starting VEGAS
+       // By invocation of compile() the expression in expr is converted into the
+       // appropriate function pointer
+       Vegas(NDIM, NCOMP, fp,
+             EPSREL, EPSABS, VERBOSE, MINEVAL, MAXEVAL, NSTART, NINCREASE,
+             &neval, &fail, integral, error, prob);
+
+       // Show the result
+       cout << "result: " << integral[0] << endl;
+
+       return 0;
+}