@@ -2,7 +2,7 @@
 
 [![Build Status](https://travis-ci.org/cirosantilli/cpp-cheat.svg?branch=master)](https://travis-ci.org/cirosantilli/cpp-cheat)
 
-C and C++ minimal examples. Asserts used wherever possible. Cheatsheets, tutorials and mini-projects.
+C and C++ minimal examples. Asserts used wherever possible. Hello worlds for cool third party libraries. Cheatsheets, tutorials and mini-projects.
 
 [Assembly Cheat](https://github.com/cirosantilli/assembly-cheat) contains lower level issues, like assembly, ELF and Binutils.
 
 
@@ -1,32 +1,44 @@
 /*
 # ctype.h
 
-    Character classficiation and conversion functions.
+    Character classification and conversion functions.
+
+# unsigned char typecast
+
+    I think it is required to avoid undefined behaviour, because
+    char may or not be signed
+    http://stackoverflow.com/questions/2054939/is-char-signed-or-unsigned-by-default
+    and ctype functions UB if input is neither fits into `unsigned char` nor is EOF.
+
+    Mentioned at: http://www.greenend.org.uk/rjk/tech/cfu.html
+
+    Conversions to unsigned types are always defined (modulo),
+    and char -> unsigned char is a bijection.
 */
 
 #include "common.h"
 
-int main() {
+int main(void) {
     /* # isspace */
     {
-        assert(isspace(' '));
-        assert(isspace('\n'));
-        assert(!isspace('a'));
+        assert(isspace((unsigned char)' '));
+        assert(isspace((unsigned char)'\n'));
+        assert(!isspace((unsigned char)'a'));
     }
 
     /* # isdigit */
     {
-        assert(isdigit('0'));
-        assert(!isdigit('a'));
+        assert(isdigit((unsigned char)'0'));
+        assert(!isdigit((unsigned char)'a'));
     }
 
     /* # ispunct */
     {
-        assert(ispunct('"'));
-        assert(ispunct('('));
-        assert(ispunct('.'));
-        assert(!ispunct('a'));
-        assert(!ispunct('0'));
+        assert(ispunct((unsigned char)'"'));
+        assert(ispunct((unsigned char)'('));
+        assert(ispunct((unsigned char)'.'));
+        assert(!ispunct((unsigned char)'a'));
+        assert(!ispunct((unsigned char)'0'));
     }
 
     /*
@@ -40,8 +52,8 @@ int main() {
         http://stackoverflow.com/questions/2661766/c-convert-a-mixed-case-string-to-all-lower-case
     */
     {
-        assert(tolower('A') == 'a');
-        assert(toupper('a') == 'A');
+        assert(tolower((unsigned char)'A') == 'a');
+        assert(toupper((unsigned char)'a') == 'A');
     }
 
     return EXIT_SUCCESS;
 
@@ -18,6 +18,10 @@
     Each error has an error message string associated to it.
     To get that error message, consider using `strerror`.
     To print an error message to stderr, consider using `perror`.
+
+    Success of calls does not normally set errno,
+    and you can and should set it yourself in most cases:
+    http://stackoverflow.com/questions/9856822/should-i-set-errno
 */
 
 #include "common.h"
 
@@ -8,6 +8,7 @@ TODO
     Currently, hitting the same not twice sounds the same as hitting it once for double the time,
     (except for the tic of phase, which is a bug as well...)
 - drum / percurssion synth
+- siren sound TODO Mechanical: https://www.youtube.com/watch?v=uckkpr2b8U8
 */
 
 #include <math.h>
 
@@ -627,9 +627,12 @@ int main() {
         Called ternary operator since it is the only operator that
         takes 3 inputs.
 
-        It seems that the only use for the ternary operator is writing less,
-        so it is completely redundant with and if else:
-        http://stackoverflow.com/questions/758849/the-ternary-conditional-operator-in-c
+        Likely exists because of CMOV instructions. But with branch preditction CMOV can be slower than if / else:
+        http://stackoverflow.com/questions/6754454/speed-difference-between-if-else-and-ternary-operator-in-c?lq=1#comment8007791_6754495
+
+        - http://stackoverflow.com/questions/758849/the-ternary-conditional-operator-in-c
+        - http://stackoverflow.com/questions/3565368/ternary-operator-vs-if-else
+        - http://stackoverflow.com/questions/6754454/speed-difference-between-if-else-and-ternary-operator-in-c?lq=1
     */
     {
         assert((1 < 2 ? 3 : 4) == 3);