expanduser: does not drop slash

this speeds up this frequently used function and reduces
function overlap

Author: scivision

+stdlib/expanduser.m

@@ -12,29 +12,25 @@
   p (1,1) string
 end
 
-e = stdlib.drop_slash(p);
+e = stdlib.posix(p);
 
 L = stdlib.len(e);
 if ~L || ~startsWith(e, "~") || (L > 1 && ~startsWith(e, "~/"))
   return
 end
 
 home = stdlib.homedir();
+if ~stdlib.len(home), return, end
 
-if stdlib.len(home) == 0
-  return
-end
-
-d = home;
 if L < 2
-  e = d;
+  e = home;
   return
 end
 
 if ischar(e)
-  e = strcat(d, '/', e(3:end));
+  e = strcat(home, '/', e(3:end));
 else
-  e = d + "/" + extractAfter(e, 2);
+  e = home + "/" + extractAfter(e, 2);
 end
 
 end

test/TestFileImpure.m

@@ -4,7 +4,7 @@
 p_is_writable = {{pwd(), true}, {"not-exists", false}, {"", false}};
 
 p_expand = {{"", ""}, {"~abc", "~abc"}, {"~", stdlib.homedir()}, ...
-  {"~/c", stdlib.homedir() + "/c"}, {'~/////c', stdlib.homedir() + "/c"}};
+  {"~/c", stdlib.homedir() + "/c"}, {'~//c', stdlib.homedir() + "//c"}};
 
 p_same = {...
 {"","", false}, ...