add and use Neighbor::modify_params() convenience function

src/MC/fix_charge_regulation.cpp

@@ -187,14 +187,7 @@ void FixChargeRegulation::init() {
     // neighbor list exclusion setup
     // turn off interactions between group all and the exclusion group
 
-    int narg = 4;
-    char **arg = new char*[narg];;
-    arg[0] = (char *) "exclude";
-    arg[1] = (char *) "group";
-    arg[2] = (char *) group_id.c_str();
-    arg[3] = (char *) "all";
-    neighbor->modify_params(narg,arg);
-    delete [] arg;
+    neighbor->modify_params(fmt::format("exclude group {} all",group_id));
   }
 
   // check that no deletable atoms are in atom->firstgroup

src/MC/fix_gcmc.cpp

@@ -580,14 +580,7 @@ void FixGCMC::init()
     // neighbor list exclusion setup
     // turn off interactions between group all and the exclusion group
 
-    int narg = 4;
-    char **arg = new char*[narg];;
-    arg[0] = (char *) "exclude";
-    arg[1] = (char *) "group";
-    arg[2] = (char *) group_id.c_str();
-    arg[3] = (char *) "all";
-    neighbor->modify_params(narg,arg);
-    delete [] arg;
+    neighbor->modify_params(fmt::format("exclude group {} all",group_id);
   }
 
   // create a new group for temporary use with selected molecules

src/MC/fix_widom.cpp

@@ -342,14 +342,7 @@ void FixWidom::init()
     // neighbor list exclusion setup
     // turn off interactions between group all and the exclusion group
 
-    int narg = 4;
-    char **arg = new char*[narg];;
-    arg[0] = (char *) "exclude";
-    arg[1] = (char *) "group";
-    arg[2] = (char *) group_id.c_str();
-    arg[3] = (char *) "all";
-    neighbor->modify_params(narg,arg);
-    delete [] arg;
+    neighbor->modify_params(fmt::format("exclude group {} all",group_id));
   }
 
   // create a new group for temporary use with selected molecules

src/USER-MISC/fix_srp.cpp

@@ -128,20 +128,10 @@ void FixSRP::init()
   // bond particles do not interact with other types
   // type bptype only interacts with itself
 
-  char* arg1[4];
-  arg1[0] = (char *) "exclude";
-  arg1[1] = (char *) "type";
-  char c0[20];
-  char c1[20];
-
   for (int z = 1; z < atom->ntypes; z++) {
     if (z == bptype)
       continue;
-    sprintf(c0, "%d", z);
-    arg1[2] = c0;
-    sprintf(c1, "%d", bptype);
-    arg1[3] = c1;
-    neighbor->modify_params(4, arg1);
+    neighbor->modify_params(fmt::format("exclude type {} {}",z,bptype));
   }
 }
 

src/neighbor.cpp

@@ -2356,6 +2356,22 @@ void Neighbor::modify_params(int narg, char **arg)
   }
 }
 
+/* ----------------------------------------------------------------------
+   convenience function to allow modifying parameters from a single string
+------------------------------------------------------------------------- */
+
+void Neighbor::modify_params(const std::string &modcmd)
+{
+  auto args = utils::split_words(modcmd);
+  char **newarg = new char*[args.size()];
+  int i=0;
+  for (const auto &arg : args) {
+    newarg[i++] = (char *)arg.c_str();
+  }
+  modify_params(args.size(),newarg);
+  delete[] newarg;
+}
+
 /* ----------------------------------------------------------------------
    remove the first group-group exclusion matching group1, group2
 ------------------------------------------------------------------------- */

src/neighbor.h

@@ -118,6 +118,7 @@ class Neighbor : protected Pointers {
   void set(int, char **);           // set neighbor style and skin distance
   void reset_timestep(bigint);      // reset of timestep counter
   void modify_params(int, char**);  // modify params that control builds
+  void modify_params(const std::string &); // convenience overload
 
   void exclusion_group_group_delete(int, int);  // rm a group-group exclusion
   int exclude_setting();            // return exclude value to accelerator pkg