diff --git a/src/USER-VTK/dump_vtk.cpp b/src/USER-VTK/dump_vtk.cpp
index 373680dfc2..92981c98ff 100644
--- a/src/USER-VTK/dump_vtk.cpp
+++ b/src/USER-VTK/dump_vtk.cpp
@@ -22,26 +22,27 @@
    Richard Berger (JKU)
 ------------------------------------------------------------------------- */
 
-#include <cmath>
-
-#include <cstring>
 #include "dump_vtk.h"
+
 #include "atom.h"
-#include "force.h"
+#include "compute.h"
 #include "domain.h"
-#include "region.h"
+#include "error.h"
+#include "fix.h"
+#include "force.h"
 #include "group.h"
 #include "input.h"
-#include "variable.h"
-#include "update.h"
-#include "modify.h"
-#include "compute.h"
-#include "fix.h"
 #include "memory.h"
-#include "error.h"
+#include "modify.h"
+#include "region.h"
+#include "update.h"
+#include "variable.h"
 
-#include <vector>
+#include <cmath>
+#include <cstring>
 #include <sstream>
+#include <vector>
+
 #include <vtkVersion.h>
 
 #ifndef VTK_MAJOR_VERSION
@@ -1731,146 +1732,123 @@ int DumpVTK::parse_fields(int narg, char **arg)
       vtype[TQZ] = Dump::DOUBLE;
       name[TQZ] = arg[iarg];
 
-    // compute value = c_ID
-    // if no trailing [], then arg is set to 0, else arg is int between []
+    } else {
 
-    } else if (strncmp(arg[iarg],"c_",2) == 0) {
-      pack_choice[ATTRIBUTES+i] = &DumpVTK::pack_compute;
-      vtype[ATTRIBUTES+i] = Dump::DOUBLE;
+      int n,tmp;
+      ArgInfo argi(arg[iarg],ArgInfo::COMPUTE|ArgInfo::FIX|ArgInfo::VARIABLE
+                   |ArgInfo::DNAME|ArgInfo::INAME);
+      argindex[ATTRIBUTES+i] = argi.get_index1();
 
-      int n = strlen(arg[iarg]);
-      char *suffix = new char[n];
-      strcpy(suffix,&arg[iarg][2]);
+      switch (argi.get_type()) {
 
-      char *ptr = strchr(suffix,'[');
-      if (ptr) {
-        if (suffix[strlen(suffix)-1] != ']')
-          error->all(FLERR,"Invalid attribute in dump vtk command");
-        argindex[ATTRIBUTES+i] = atoi(ptr+1);
-        *ptr = '\0';
-      } else argindex[ATTRIBUTES+i] = 0;
+      case ArgInfo::UNKNOWN:
+        error->all(FLERR,"Invalid attribute in dump vtk command");
+        break;
 
-      n = modify->find_compute(suffix);
-      if (n < 0) error->all(FLERR,"Could not find dump vtk compute ID");
-      if (modify->compute[n]->peratom_flag == 0)
-        error->all(FLERR,"Dump vtk compute does not compute per-atom info");
-      if (argindex[ATTRIBUTES+i] == 0 && modify->compute[n]->size_peratom_cols > 0)
-        error->all(FLERR,
-                   "Dump vtk compute does not calculate per-atom vector");
-      if (argindex[ATTRIBUTES+i] > 0 && modify->compute[n]->size_peratom_cols == 0)
-        error->all(FLERR,\
-                   "Dump vtk compute does not calculate per-atom array");
-      if (argindex[ATTRIBUTES+i] > 0 &&
-          argindex[ATTRIBUTES+i] > modify->compute[n]->size_peratom_cols)
-        error->all(FLERR,"Dump vtk compute vector is accessed out-of-range");
+        // compute value = c_ID
+        // if no trailing [], then arg is set to 0, else arg is int between []
 
-      field2index[ATTRIBUTES+i] = add_compute(suffix);
-      name[ATTRIBUTES+i] = arg[iarg];
-      delete [] suffix;
+      case ArgInfo::COMPUTE:
+        pack_choice[ATTRIBUTES+i] = &DumpVTK::pack_compute;
+        vtype[ATTRIBUTES+i] = Dump::DOUBLE;
 
-    // fix value = f_ID
-    // if no trailing [], then arg is set to 0, else arg is between []
+        n = modify->find_compute(argi.get_name());
+        if (n < 0) error->all(FLERR,"Could not find dump vtk compute ID");
+        if (modify->compute[n]->peratom_flag == 0)
+          error->all(FLERR,"Dump vtk compute does not compute per-atom info");
+        if (argi.get_dim() == 0 && modify->compute[n]->size_peratom_cols > 0)
+          error->all(FLERR,
+                     "Dump vtk compute does not calculate per-atom vector");
+        if (argi.get_dim() > 0 && modify->compute[n]->size_peratom_cols == 0)
+          error->all(FLERR,
+                     "Dump vtk compute does not calculate per-atom array");
+        if (argi.get_dim() > 0 &&
+            argi.get_index1() > modify->compute[n]->size_peratom_cols)
+          error->all(FLERR,"Dump vtk compute vector is accessed out-of-range");
 
-    } else if (strncmp(arg[iarg],"f_",2) == 0) {
-      pack_choice[ATTRIBUTES+i] = &DumpVTK::pack_fix;
-      vtype[ATTRIBUTES+i] = Dump::DOUBLE;
+        field2index[ATTRIBUTES+i] = add_compute(argi.get_name());
+        name[ATTRIBUTES+i] = arg[iarg];
+        break;
 
-      int n = strlen(arg[iarg]);
-      char *suffix = new char[n];
-      strcpy(suffix,&arg[iarg][2]);
+        // fix value = f_ID
+        // if no trailing [], then arg is set to 0, else arg is between []
 
-      char *ptr = strchr(suffix,'[');
-      if (ptr) {
-        if (suffix[strlen(suffix)-1] != ']')
-          error->all(FLERR,"Invalid attribute in dump vtk command");
-        argindex[ATTRIBUTES+i] = atoi(ptr+1);
-        *ptr = '\0';
-      } else argindex[ATTRIBUTES+i] = 0;
+      case ArgInfo::FIX:
+        pack_choice[ATTRIBUTES+i] = &DumpVTK::pack_fix;
+        vtype[ATTRIBUTES+i] = Dump::DOUBLE;
 
-      n = modify->find_fix(suffix);
-      if (n < 0) error->all(FLERR,"Could not find dump vtk fix ID");
-      if (modify->fix[n]->peratom_flag == 0)
-        error->all(FLERR,"Dump vtk fix does not compute per-atom info");
-      if (argindex[ATTRIBUTES+i] == 0 && modify->fix[n]->size_peratom_cols > 0)
-        error->all(FLERR,"Dump vtk fix does not compute per-atom vector");
-      if (argindex[ATTRIBUTES+i] > 0 && modify->fix[n]->size_peratom_cols == 0)
-        error->all(FLERR,"Dump vtk fix does not compute per-atom array");
-      if (argindex[ATTRIBUTES+i] > 0 &&
-          argindex[ATTRIBUTES+i] > modify->fix[n]->size_peratom_cols)
-        error->all(FLERR,"Dump vtk fix vector is accessed out-of-range");
+        n = modify->find_fix(argi.get_name());
+        if (n < 0) error->all(FLERR,"Could not find dump vtk fix ID");
+        if (modify->fix[n]->peratom_flag == 0)
+          error->all(FLERR,"Dump vtk fix does not compute per-atom info");
+        if (argi.get_dim() == 0 && modify->fix[n]->size_peratom_cols > 0)
+          error->all(FLERR,"Dump vtk fix does not compute per-atom vector");
+        if (argi.get_dim() > 0 && modify->fix[n]->size_peratom_cols == 0)
+          error->all(FLERR,"Dump vtk fix does not compute per-atom array");
+        if (argi.get_dim() > 0 &&
+            argi.get_index1() > modify->fix[n]->size_peratom_cols)
+          error->all(FLERR,"Dump vtk fix vector is accessed out-of-range");
 
-      field2index[ATTRIBUTES+i] = add_fix(suffix);
-      name[ATTRIBUTES+i] = arg[iarg];
-      delete [] suffix;
+        field2index[ATTRIBUTES+i] = add_fix(argi.get_name());
+        name[ATTRIBUTES+i] = arg[iarg];
+        break;
 
-    // variable value = v_name
+        // variable value = v_name
 
-    } else if (strncmp(arg[iarg],"v_",2) == 0) {
-      pack_choice[ATTRIBUTES+i] = &DumpVTK::pack_variable;
-      vtype[ATTRIBUTES+i] = Dump::DOUBLE;
+      case ArgInfo::VARIABLE:
+        pack_choice[ATTRIBUTES+i] = &DumpVTK::pack_variable;
+        vtype[ATTRIBUTES+i] = Dump::DOUBLE;
 
-      int n = strlen(arg[iarg]);
-      char *suffix = new char[n];
-      strcpy(suffix,&arg[iarg][2]);
+        n = input->variable->find(argi.get_name());
+        if (n < 0) error->all(FLERR,"Could not find dump vtk variable name");
+        if (input->variable->atomstyle(n) == 0)
+          error->all(FLERR,"Dump vtk variable is not atom-style variable");
 
-      argindex[ATTRIBUTES+i] = 0;
+        field2index[ATTRIBUTES+i] = add_variable(argi.get_name());
+        name[ATTRIBUTES+i] = arg[iarg];
+        break;
 
-      n = input->variable->find(suffix);
-      if (n < 0) error->all(FLERR,"Could not find dump vtk variable name");
-      if (input->variable->atomstyle(n) == 0)
-        error->all(FLERR,"Dump vtk variable is not atom-style variable");
+        // custom per-atom floating point value = d_ID
 
-      field2index[ATTRIBUTES+i] = add_variable(suffix);
-      name[ATTRIBUTES+i] = suffix;
-      delete [] suffix;
+      case ArgInfo::DNAME:
+        pack_choice[ATTRIBUTES+i] = &DumpVTK::pack_custom;
+        vtype[ATTRIBUTES+i] = Dump::DOUBLE;
 
-    // custom per-atom floating point value = d_ID
+        tmp = -1;
+        n = atom->find_custom(argi.get_name(),tmp);
+        if (n < 0)
+          error->all(FLERR,"Could not find custom per-atom property ID");
 
-    } else if (strncmp(arg[iarg],"d_",2) == 0) {
-      pack_choice[ATTRIBUTES+i] = &DumpVTK::pack_custom;
-      vtype[ATTRIBUTES+i] = Dump::DOUBLE;
+        if (tmp != 1)
+          error->all(FLERR,"Custom per-atom property ID is not floating point");
 
-      int n = strlen(arg[iarg]);
-      char *suffix = new char[n];
-      strcpy(suffix,&arg[iarg][2]);
-      argindex[ATTRIBUTES+i] = 0;
+        field2index[ATTRIBUTES+i] = add_custom(argi.get_name(),1);
+        name[ATTRIBUTES+i] = arg[iarg];
+        break;
 
-      int tmp = -1;
-      n = atom->find_custom(suffix,tmp);
-      if (n < 0)
-        error->all(FLERR,"Could not find custom per-atom property ID");
+        // custom per-atom integer value = i_ID
 
-      if (tmp != 1)
-        error->all(FLERR,"Custom per-atom property ID is not floating point");
+      case ArgInfo::INAME:
+        pack_choice[ATTRIBUTES+i] = &DumpVTK::pack_custom;
+        vtype[ATTRIBUTES+i] = Dump::INT;
 
-      field2index[ATTRIBUTES+i] = add_custom(suffix,1);
-      name[ATTRIBUTES+i] = suffix;
-      delete [] suffix;
+        tmp = -1;
+        n = atom->find_custom(argi.get_name(),tmp);
+        if (n < 0)
+          error->all(FLERR,"Could not find custom per-atom property ID");
 
-    // custom per-atom integer value = i_ID
+        if (tmp != 0)
+          error->all(FLERR,"Custom per-atom property ID is not integer");
 
-    } else if (strncmp(arg[iarg],"i_",2) == 0) {
-      pack_choice[ATTRIBUTES+i] = &DumpVTK::pack_custom;
-      vtype[ATTRIBUTES+i] = Dump::INT;
+        field2index[ATTRIBUTES+i] = add_custom(argi.get_name(),0);
+        name[ATTRIBUTES+i] = arg[iarg];
+        break;
 
-      int n = strlen(arg[iarg]);
-      char *suffix = new char[n];
-      strcpy(suffix,&arg[iarg][2]);
-      argindex[ATTRIBUTES+i] = 0;
-
-      int tmp = -1;
-      n = atom->find_custom(suffix,tmp);
-      if (n < 0)
-        error->all(FLERR,"Could not find custom per-atom property ID");
-
-      if (tmp != 0)
-        error->all(FLERR,"Custom per-atom property ID is not integer");
-
-      field2index[ATTRIBUTES+i] = add_custom(suffix,0);
-      name[ATTRIBUTES+i] = suffix;
-      delete [] suffix;
-
-    } else return iarg;
+      default:
+        return iarg;
+        break;
+      }
+    }
   }
 
   identify_vectors();
diff --git a/src/fix_ave_histo_weight.cpp b/src/fix_ave_histo_weight.cpp
index 652136f9c6..ae83d80845 100644
--- a/src/fix_ave_histo_weight.cpp
+++ b/src/fix_ave_histo_weight.cpp
@@ -16,28 +16,28 @@
 ------------------------------------------------------------------------- */
 #include "fix_ave_histo_weight.h"
 
-#include <unistd.h>
-#include "fix.h"
+#include "arg_info.h"
 #include "atom.h"
-#include "update.h"
-#include "modify.h"
 #include "compute.h"
-#include "input.h"
-#include "variable.h"
-#include "memory.h"
 #include "error.h"
+#include "fix.h"
+#include "input.h"
+#include "memory.h"
+#include "modify.h"
+#include "update.h"
+#include "variable.h"
+
+#include <unistd.h>
 
 using namespace LAMMPS_NS;
 using namespace FixConst;
 
-enum{X,V,F,COMPUTE,FIX,VARIABLE};
 enum{ONE,RUNNING};
 enum{SCALAR,VECTOR,WINDOW};
 enum{DEFAULT,GLOBAL,PERATOM,LOCAL};
 enum{IGNORE,END,EXTRA};
 enum{SINGLE,VALUE};
 
-
 #define BIG 1.0e20
 
 /* ---------------------------------------------------------------------- */
@@ -54,31 +54,31 @@ FixAveHistoWeight::FixAveHistoWeight(LAMMPS *lmp, int narg, char **arg) :
   int size[2];
 
   for (int i = 0; i < nvalues; i++) {
-    if (which[i] == X || which[i] == V || which[i] == F) {
+    if (which[i] == ArgInfo::X || which[i] == ArgInfo::V || which[i] == ArgInfo::F) {
       size[i] = atom->nlocal;
-    } else if (which[i] == COMPUTE && kind == GLOBAL && mode == SCALAR) {
+    } else if (which[i] == ArgInfo::COMPUTE && kind == GLOBAL && mode == SCALAR) {
       int icompute = modify->find_compute(ids[i]);
       size[i] = modify->compute[icompute]->size_vector;
-    } else if (which[i] == COMPUTE && kind == GLOBAL && mode == VECTOR) {
+    } else if (which[i] == ArgInfo::COMPUTE && kind == GLOBAL && mode == VECTOR) {
       int icompute = modify->find_compute(ids[i]);
       size[i] = modify->compute[icompute]->size_array_rows;
-    } else if (which[i] == COMPUTE && kind == PERATOM) {
+    } else if (which[i] == ArgInfo::COMPUTE && kind == PERATOM) {
       size[i] = atom->nlocal;
-    } else if (which[i] == COMPUTE && kind == LOCAL) {
+    } else if (which[i] == ArgInfo::COMPUTE && kind == LOCAL) {
       int icompute = modify->find_compute(ids[i]);
       size[i] = modify->compute[icompute]->size_local_rows;
-    } else if (which[i] == FIX && kind == GLOBAL && mode == SCALAR) {
+    } else if (which[i] == ArgInfo::FIX && kind == GLOBAL && mode == SCALAR) {
       int ifix = modify->find_fix(ids[i]);
       size[i] = modify->fix[ifix]->size_vector;
-    } else if (which[i] == FIX && kind == GLOBAL && mode == VECTOR) {
+    } else if (which[i] == ArgInfo::FIX && kind == GLOBAL && mode == VECTOR) {
       int ifix = modify->find_fix(ids[i]);
       size[i]= modify->fix[ifix]->size_array_rows;
-    } else if (which[i] == FIX && kind == PERATOM) {
+    } else if (which[i] == ArgInfo::FIX && kind == PERATOM) {
       size[i] = atom->nlocal;
-    } else if (which[i] == FIX && kind == LOCAL) {
+    } else if (which[i] == ArgInfo::FIX && kind == LOCAL) {
       int ifix = modify->find_fix(ids[i]);
       size[i] = modify->fix[ifix]->size_local_rows;
-    } else if (which[i] == VARIABLE && kind == PERATOM) {
+    } else if (which[i] == ArgInfo::VARIABLE && kind == PERATOM) {
       size[i] = atom->nlocal;
     }
   }
@@ -130,21 +130,21 @@ void FixAveHistoWeight::end_of_step()
 
   // atom attributes
 
-  if (which[i] == X) {
+  if (which[i] == ArgInfo::X) {
     weights = &atom->x[0][j];
     stride = 3;
-  } else if (which[i] == V) {
+  } else if (which[i] == ArgInfo::V) {
     weights = &atom->v[0][j];
     stride = 3;
     bin_atoms(&atom->v[0][j],3);
-  } else if (which[i] == F) {
+  } else if (which[i] == ArgInfo::F) {
     weights = &atom->f[0][j];
     stride = 3;
   }
 
   // invoke compute if not previously invoked
 
-  if (which[i] == COMPUTE) {
+  if (which[i] == ArgInfo::COMPUTE) {
 
     Compute *compute = modify->compute[m];
 
@@ -206,7 +206,7 @@ void FixAveHistoWeight::end_of_step()
 
   // access fix fields, guaranteed to be ready
 
-  } else if (which[i] == FIX) {
+  } else if (which[i] == ArgInfo::FIX) {
 
     Fix *fix = modify->fix[m];
 
@@ -243,10 +243,10 @@ void FixAveHistoWeight::end_of_step()
 
   // evaluate equal-style variable
 
-  } else if (which[i] == VARIABLE && kind == GLOBAL) {
+  } else if (which[i] == ArgInfo::VARIABLE && kind == GLOBAL) {
     weight = input->variable->compute_equal(m);
 
-  } else if (which[i] == VARIABLE && kind == PERATOM) {
+  } else if (which[i] == ArgInfo::VARIABLE && kind == PERATOM) {
     if (atom->nmax > maxatom) {
       memory->destroy(vector);
       maxatom = atom->nmax;
@@ -265,16 +265,16 @@ void FixAveHistoWeight::end_of_step()
 
   // atom attributes
 
-  if (which[i] == X && weights != nullptr)
+  if (which[i] == ArgInfo::X && weights != nullptr)
     bin_atoms_weights(&atom->x[0][j],3,weights,stride);
-  else if (which[i] == V && weights != nullptr)
+  else if (which[i] == ArgInfo::V && weights != nullptr)
     bin_atoms_weights(&atom->v[0][j],3,weights,stride);
-  else if (which[i] == F && weights != nullptr)
+  else if (which[i] == ArgInfo::F && weights != nullptr)
     bin_atoms_weights(&atom->f[0][j],3,weights,stride);
 
   // invoke compute if not previously invoked
 
-  if (which[i] == COMPUTE) {
+  if (which[i] == ArgInfo::COMPUTE) {
     Compute *compute = modify->compute[m];
     if (kind == GLOBAL && mode == SCALAR) {
       if (j == 0) {
@@ -335,7 +335,7 @@ void FixAveHistoWeight::end_of_step()
 
     // access fix fields, guaranteed to be ready
 
-  } else if (which[i] == FIX) {
+  } else if (which[i] == ArgInfo::FIX) {
 
     Fix *fix = modify->fix[m];
 
@@ -372,10 +372,10 @@ void FixAveHistoWeight::end_of_step()
 
     // evaluate equal-style variable
 
-  } else if (which[i] == VARIABLE && kind == GLOBAL) {
+  } else if (which[i] == ArgInfo::VARIABLE && kind == GLOBAL) {
     bin_one_weights(input->variable->compute_equal(m),weight);
 
-  } else if (which[i] == VARIABLE && kind == PERATOM) {
+  } else if (which[i] == ArgInfo::VARIABLE && kind == PERATOM) {
     if (atom->nmax > maxatom) {
       memory->destroy(vector);
       maxatom = atom->nmax;