Fix phrase related to "cout" but not relevant for print. (#4)

* Fix phrase related to "cout" but not relevant for print.

* Fix cast of char8_t to char. Has to use reinterpret_cast.

* acos and constexpr with clang++
Removed `-lm` requirement for `acos` on MacOS.

Added a comment about `acos` not being constexpr in some cmath implementations (clang++ for example).

* missing noexcept keyword in code sample

The keyword needs to be on `throw_if_zero` to demonstrate termination due to uncaught exception.

Author: gaspard

01-string-and-character-literals.md

@@ -133,7 +133,7 @@ While little hands make vain pretence
 Our wanderings to guide.
 ```
 
-* Now use a (non-raw) string literal for each line and a single call to `print()` with suitable escape characters. What happens if you remove all of the stream insertion operators *except* for the first? (Explanation: *concatenation* of adjacent string literals is automatically performed by the pre-processor.)
+* Now use a (non-raw) string literal for each line and a single call to `print()` with suitable escape characters. You concatenate the string literals without any operator: *concatenation* of adjacent string literals is automatically performed by the pre-processor.
 
 * Modify `01-title.cpp` to output the title of your favorite book or film centered on the console window (assume an 80 character fixed width, and change the size of the console window if different).
 
@@ -156,7 +156,7 @@ The following table lists C++ types, sizes, target encodings, literals and objec
 | char32_t |   32  |  UTF-32  |     U"abcd"    |        U'a'       |     UR"(abcd)"     |  u32string  |      n/a      |   no    |
 |  wchar_t | 16/32 |   n/a +  |     L"abcd"    |        L'a'       |     LR"(abcd)"     |   wstring   |  wcout/wcerr  |   no    |
 
-&#42; An explicit cast to type `char` in `operator<<` may be required when using `cout`/`cerr`, for example: `cout << static_cast<char>(u8"Hello \u20AC!\n");`.
+&#42; An explicit cast to type `char` in `operator<<` may be required when using `cout`/`cerr`, for example: `cout << reinterpret_cast<const char*>(u8"Hello \u20AC!\n");`.
 
 &#43; The `wchar_t` encoding and streams under Windows are 16-bit and support UTF-16.
 

02-variables-scopes-and-namespaces.md

@@ -468,6 +468,9 @@ In fact, `constexpr` expressions can be complex with recent compilers, as long a
 #include <cmath>
 using namespace std;
 
+// Note: currently, not all compilers mark `acos` as a
+// constexpr function in cmath. The following line might
+// not compile with `clang++` for example.
 constexpr double PI1 = acos(-1.0);
 constexpr double PI2 = 22.0 / 7.0;
 
@@ -480,7 +483,7 @@ int main() {
 }
 ```
 
-(Hint: this program is the first to require an additional header to `<print>`; you may need to add `-lm` to the compile command under Linux/MacOS in order to link in the math library containing the `acos()` function.)
+(Hint: this program is the first to require an additional header to `<print>`; you may need to add `-lm` to the compile command under Linux in order to link in the math library containing the `acos()` function.)
 
 **Experiment**
 

04-functions.md

@@ -538,7 +538,7 @@ The keyword `noexcept` is used to declare that a function is guaranteed to not t
 #include <stdexcept>
 using namespace std;
 
-void throw_if_zero(int i) {
+void throw_if_zero(int i) noexcept {
     if (!i) {
         throw runtime_error("found a zero");
     }