[GiNaC-list] problem with function pow

[Saurav Pathak]

I am resending this mail.  This is a very critical issue for me.
I absolutely must be able to change a string into an expression.
And if I am doing it wrong, please show it to me.  

Thanks,
Saurav


Saurav Pathak [Mon, Jan 30, 2006 at 07:31:20PM -0500]:

+  hi,
+  
+  i am having trouble turning a string with function "pow" into an
+  expression.  an example of the code is given below along with the 
+  output.  i cannot figure out what i am doing wrong.
+  
+  thanks for your help in advance.
+  --------
+  #include <iostream>
+  #include <string>
+  #include <ginac/ginac.h>
+  #include <ginac/power.h>
+  using namespace std;
+  using namespace GiNaC;
+  
+  int main()
+  {
+      lst all;
+      all.append(symbol("x"));
+  
+      // no pow
+      string str2 = "x*x";
+      ex e2(str2, all);
+      cout << "nopow : " << e2 << endl;
+  
+      // with pow
+      string str = "pow(x, 2)";
+      ex e(str, all);
+      cout << "withpow: " << e << endl;
+  
+      return 0;
+  }
+  
+  the output is:
+  nopow : x^2
+  terminate called after throwing an instance of 'std::runtime_error'
+    what():  no function 'pow' with 2 parameters defined
+  Aborted
+  --------------------
+  -- 
+  saurav