Revert "Revert "Revert "Revert "Cleanup some numeric code.""""

core/src/fpdftext/fpdf_text.cpp

Index: core/src/fpdftext/fpdf_text.cpp
diff --git a/core/src/fpdftext/fpdf_text.cpp b/core/src/fpdftext/fpdf_text.cpp
index 9ecbc21bdac06bea0d72dc3a1584b27cb75e3966..3c4a90e59e083d5b7c68066eaa4d1119757226c5 100644
--- a/core/src/fpdftext/fpdf_text.cpp
+++ b/core/src/fpdftext/fpdf_text.cpp
@@ -4,6 +4,8 @@
 
 // Original code copyright 2014 Foxit Software Inc. http://www.foxitsoftware.com
 
+#include <cctype>
+
 #include "../../../third_party/base/nonstd_unique_ptr.h"
 #include "../../include/fpdfapi/fpdf_page.h"
 #include "../../include/fpdfapi/fpdf_pageobj.h"
@@ -436,10 +438,8 @@ void NormalizeString(CFX_WideString& str) {
 static FX_BOOL IsNumber(CFX_WideString& str) {
   for (int i = 0; i < str.GetLength(); i++) {
     FX_WCHAR ch = str[i];
-    if ((ch < '0' || ch > '9') && ch != '-' && ch != '+' && ch != '.' &&
-        ch != ' ') {
+    if (!std::isdigit(ch) && ch != '-' && ch != '+' && ch != '.' && ch != ' ')
       return FALSE;
-    }
   }
   return TRUE;
 }