added primes.h/.cpp (contains precomputed primes)

Installation/src/CGAL/all_files.cpp

@@ -23,3 +23,4 @@
 #include "Real_timer.cpp"
 #include "Timer.cpp"
 #include "Turkowski_numeric_solver.cpp"
+#include "primes.cpp"

Modular_arithmetic/include/CGAL/primes.h

@@ -0,0 +1,45 @@
+
+#ifndef CGAL_PRIMES_H
+#define CGAL_PRIMES_H
+
+#include <CGAL/basic.h>
+
+namespace CGAL { 
+namespace CGALi {
+extern int primes[2000];
+
+static inline 
+int get_next_lower_prime(int current_prime){
+    bool is_prime = false;
+    
+    int i;
+    CGAL_precondition_msg(current_prime != 2 ," primes definitely exhausted ");
+
+    if((current_prime <= 7) && (current_prime > 2)){
+        if(current_prime <= 5){
+            if(current_prime == 3)
+                return 2;
+            return 3;
+        }
+        return 5;
+    }                
+    for(i=current_prime-2;(i>1 && !is_prime);i=i-2){
+        int r = 1;
+        for(int j=3; (j <= i/2 && (r != 0)); j++){
+            r = i % j;
+//                std::cout<<"i " <<i<<std::endl;
+//                std::cout<<"j " <<j<<std::endl;
+//                std::cout<<"i%j " <<i%j<<std::endl;
+            if(j==i/2 && r != 0)
+                is_prime = true;
+        }
+    }
+//    CGAL_precondition_msg(is_prime," primes definitely exhausted ");
+    return i+2;
+}
+
+
+}
+}
+
+#endif // CGAL_PRIMES_H