Enhancing of error message

Author: Divendra2006

po/fr.po

@@ -1301,8 +1301,8 @@ msgid "Unknown 'measure.vars' type %s at index %d of list"
 msgstr "Type inconnu de 'measure.vars' %s à l'indice %d de la liste"
 
 #: fmelt.c:187
-msgid "One or more values in 'measure.vars' is invalid."
-msgstr "Une ou plusieurs valeurs de 'measure.vars' ne sont pas valides."
+msgid "One or more values in 'measure.vars' is invalid; please fix by removing: %s"
+msgstr "Une ou plusieurs valeurs de 'measure.vars' ne sont pas valides; veuillez corriger en supprimant : %s"
 
 #: fmelt.c:189
 msgid "One or more values in 'id.vars' is invalid."

po/zh_CN.po

@@ -1154,8 +1154,8 @@ msgid "Unknown 'measure.vars' type %s at index %d of list"
 msgstr "未知'measure.vars'类型 %s，位于列表中 %d"
 
 #: fmelt.c:187
-msgid "One or more values in 'measure.vars' is invalid."
-msgstr "'measure.vars'里，一或多个数值无效"
+msgid "One or more values in 'measure.vars' is invalid; please fix by removing: %s"
+msgstr "'measure.vars'里，一或多个数值无效；请通过删除以下数值来修复：%s"
 
 #: fmelt.c:189
 msgid "One or more values in 'id.vars' is invalid."

src/fmelt.c

@@ -1,5 +1,7 @@
 #include "data.table.h"
 #include <Rdefines.h>
+
+
 // #include <signal.h> // the debugging machinery + breakpoint aidee
 // raise(SIGINT);
 
@@ -176,8 +178,12 @@ bool is_default_measure(SEXP vec) {
 
 // maybe unlist, then unique, then set_diff.
 SEXP uniq_diff(SEXP int_or_list, int ncol, bool is_measure) {
+  // Protect input list/vector, unlisting if necessary
   SEXP int_vec = PROTECT(isNewList(int_or_list) ? unlist_(int_or_list) : int_or_list);
+  
+  // Check for duplicated elements in the input vector
   SEXP is_duplicated = PROTECT(duplicated(int_vec, FALSE)); 
+  
   int n_unique_cols = 0;
   SEXP invalid_columns = PROTECT(allocVector(INTSXP, length(int_vec)));
   int* invalid_col_ptr = INTEGER(invalid_columns);
@@ -206,16 +212,23 @@ SEXP uniq_diff(SEXP int_or_list, int ncol, bool is_measure) {
   }
   SEXP unique_col_numbers = PROTECT(allocVector(INTSXP, n_unique_cols)); 
   int unique_i = 0;
-  for (int i=0; i<length(is_duplicated); ++i) {
+  
+  // Populate the unique column numbers into the new vector
+  for (int i = 0; i < length(is_duplicated); ++i) {
     if (!LOGICAL(is_duplicated)[i]) {
       INTEGER(unique_col_numbers)[unique_i++] = INTEGER(int_vec)[i];
     }
   }
+  
+  // Apply set difference to get final unique column indices
   SEXP out = set_diff(unique_col_numbers, ncol);
   UNPROTECT(4);
   return out;
 }
 
+
+
+
 SEXP cols_to_int_or_list(SEXP cols, SEXP dtnames, bool is_measure) {
   switch(TYPEOF(cols)) {
   case STRSXP  : return chmatch(cols, dtnames, 0);