Add function 'remzerovec' to remove vectors of length 0

from current plot. Maybe of interest if you have option
savecurrents, write xx all, and ac generates length 0 vectors

src/frontend/commands.c

@@ -236,6 +236,10 @@ struct comm spcp_coms[] = {
       { 040000, 040000, 040000, 040000 }, E_DEFHMASK, 1, LOTS,
       NULL,
       "varname ... : Undefine vectors." } ,
+    { "remzerovec", com_remzerovec, FALSE, FALSE,
+        { 040000, 040000, 040000, 040000 }, E_DEFHMASK, 0, LOTS,
+        NULL,
+        "remove zero length vectors." } ,
     { "print", com_print, FALSE, TRUE,
       { 040000, 040000, 040000, 040000 }, E_BEGINNING, 1, LOTS,
       arg_print,
@@ -716,6 +720,10 @@ struct comm nutcp_coms[] = {
       { 040000, 040000, 040000, 040000 }, E_DEFHMASK, 1, LOTS,
       NULL,
       "varname ... : Undefine vectors." } ,
+    { "remzerovec", com_remzerovec, FALSE, FALSE,
+      { 040000, 040000, 040000, 040000 }, E_DEFHMASK, 0, LOTS,
+      NULL,
+      "remove zero length vectors." },
     { "print", com_print, FALSE, TRUE,
       { 040000, 040000, 040000, 040000 }, E_BEGINNING, 1, LOTS,
       arg_print,

src/frontend/postcoms.c

@@ -71,6 +71,23 @@ com_unlet(wordlist *wl)
 } /* end of function com_unlet */
 
 
+/* Remove zero length vectors in the wordlist from the current plot */
+void
+com_remzerovec(wordlist* wl)
+{
+    NG_IGNORE(wl);
+    
+    struct dvec* ov;
+
+    for (ov = plot_cur->pl_dvecs; ov; ov = ov->v_next) {
+        if (ov->v_length == 0) {
+            ov->v_flags &= ~VF_PERMANENT;
+            /* Remove from the keyword list. */
+            cp_remkword(CT_VECTOR, ov->v_name);
+        }
+    } /* end of loop over vectors to delete */
+} /* end of function com_remzerovec */
+
 
 /* Load in a file. */
 void

src/frontend/postcoms.h

@@ -15,6 +15,7 @@ void com_transpose(wordlist *wl);
 void com_cross(wordlist *wl);
 void com_destroy(wordlist *wl);
 void com_splot(wordlist *wl);
+void com_remzerovec(wordlist* wl);
 
 void destroy_const_plot(void);