Moved density_clear to utils

  This version also includes the 5% or lower navhaz adjustment.

utils.cpp

@@ -157,6 +157,48 @@ bool at_planet_prompt(const std::string &prompt) {
   return false;
 }
 
+bool density_clear(int sector, int density, int navhaz) {
+  if(sector == 0) return false;
+  //if(anomoly) return false;
+  /*
+  http://wiki.classictw.com/index.php?title=Gypsy%27s_Big_Dummy%27s_Guide_to_TradeWars_Text#Trader_Information
+  Density Readings:
+    0 = Empty Sector or Ferrengi Dreadanought
+    1 = Marker Beacon
+    2 = Limpet Type 2 Tracking Mine
+    5 = Fighter (per Fighter)
+   10 = Armid Type 1 Mine
+   21 = Navigation Hazard (Per 1 Percent)
+   21 = Destroyed Ship     (Due to 1 Percent Nav-Haz)
+   38 = Unmanned Ship
+   40 = Manned Ship, Alien or Ferrengi Assault Trader
+   50 = Destroyed Starport (After 25 Percent Nav-Haz Clears)
+  100 = Starport or Ferrengi Battle Cruiser
+  210 = Destroyed Planet   (Due to 10 Percent Nav-Haz)
+  462 = Federation Starship under Admiral Nelson
+  489 = Federation Starship under Captain Zyrain
+  500 = Planet
+  512 = Federation Starship under Admiral Clausewitz
+  575 = Destroyed Port (Before 25% Nav-Haz Clears)
+  */
+  int dense = density;
+  if((navhaz != 0) && (navhaz <= 5)) {
+    // Adjust density by upto 5% navhaz, exlude greather than 5%
+    dense -= navhaz * 21;
+  }
+  if(navhaz > 5) return false;
+  switch (dense) {
+    case 0:
+    case 1:
+    case 100:
+    case 101:
+      return true;
+  }
+  // Special case for Sector 001.
+  if((sector == 1) && (dense == 601)) return true;
+  return false;
+}
+
 #include <algorithm>
 #include <cctype>
 

utils.h

@@ -21,6 +21,8 @@ bool endswith(const std::string &line, const std::string &has);
 bool in(const std::string &line, const std::string &has);
 std::string repr(const std::string &source);
 
+bool density_clear(int sector, int density, int navhaz=0);
+
 bool file_exists(const std::string &name);
 bool at_command_prompt(const std::string &prompt);
 bool at_computer_prompt(const std::string &prompt);