Re: Visual D 0.47.0 released
On 26/06/2018 16:25, Robert M. Münch wrote: On 2018-06-24 13:08:53 +, Rainer Schuetze said: a new release of Visual D has just been uploaded. Major changes are * improved Visual C++ project integration: better dependencies, automatic libraries, name demangling * new project wizard * mago debugger: show vtable, dynamic type of interfaces, symbol names of pointer address As soon as I use the Mago debugger, it's impossible to start a debugging session. Any idea how to track down such a problem? Works for me, can you give more details? VS version, platform, etc. Please note that there is no need to select the Mago debug engine in VS2013 or later. Since a couple of versions of Visual D, the VS debugger is equipped with an extension based on Mago that can evaluate D expressions.
Re: Catching std.conv.ConvException in readf causes a buffer overrun
On Wednesday, 27 June 2018 at 02:39:49 UTC, Shigeki Karita wrote:
import std.stdio;
import std.conv;
void main() {
int i;
try {
readf("%d\n", &i); // "a"
} catch (ConvException e) {
auto s = readln();
writeln(s); // "aa", "aaa" or SEGV ???
}
}
https://wandbox.org/permlink/NMYNjpOgQtfUprBQ
I just want to retry reading if input was invalid. How can I do
it?
I found that formattedRead!"%d\n"(readln(), i) can avoid the
buffer overrun why readf cannot do this?
---
import std.stdio;
import std.format;
import std.stdio;
import std.format;
void main() {
int i;
try {
formattedRead!"%d\n"(readln(), i);
} catch (Exception e) {
// writeln(e);
auto s = readln();
writeln(s); // ""
}
}
Catching std.conv.ConvException in readf causes a buffer overrun
import std.stdio;
import std.conv;
void main() {
int i;
try {
readf("%d\n", &i); // "a"
} catch (ConvException e) {
auto s = readln();
writeln(s); // "aa", "aaa" or SEGV ???
}
}
https://wandbox.org/permlink/NMYNjpOgQtfUprBQ
I just want to retry reading if input was invalid. How can I do
it?
Re: CustomString and string constraints
On Tuesday, 26 June 2018 at 22:16:28 UTC, Jonathan M Davis wrote: If what you're asking is whether it's possible for a template constraint that uses something like isSomeString will ever match a user-defined type, then the answer is no. Thats exactly what I wanted xD. My idea was that if you can make custom array types that operate with phobos lib(via some implicit conversions) then there "should" have a way to do that with strings, but I understood the issues that you explained. Thanks!
Re: CustomString and string constraints
n Tuesday, June 26, 2018 17:14:08 SrMordred via Digitalmars-d-learn wrote:
> Is possible to make a Custom Struct String work for D string
> constraints?
>
> eg:
>
> struct MyString
> {
> char[] arr;
> alias arr this;
> }
>
> void getString( char[] str ){}
>
> MyString().split(";"); //oops, type mismatch
>
> getString( MyString() ); //fine, implicit conversion
>
> isSomeString!(char[]).writeln; //true
> isSomeString!(MyString).writeln; //false
If what you're asking is whether it's possible for a template constraint
that uses something like isSomeString will ever match a user-defined type,
then the answer is no. isSomeString specifically requires that the type be a
string. And it actually would be fairly error-prone if it accepted anything
else.
If a template is written with the assumption that it's going to be operating
on arrays of characters, and it accepts anything that implicitly converts to
an array of characters, then you easily get subtle bugs (e.g. some parts of
the code could use the actual type and others would do the implicit
conversion rather than the code consistently using the same type). Any
template that accepts an implicit conversion really needs to force that
conversion rather than trying to operate on a type that implicitly converts
to a particular type as if it were that type. But in general, it's just far
less error-prone to require that the caller do the conversion.
And implicit conversions to dynamic arrays (strings included) are
particularly dangerous to allow. For instance, if you have a function that
does something like
T[] foo(T[] arr)
{
...
return arr[i .. j];
}
and you pass it a T[42], then the implicit conversion is done at the call
site, and the slice that is returned is valid and will continue to be valid
so long as the static array has not been destroyed. However, if you do
something like
T[] foo(U)(U arr)
if(is(U : T[]))
{
...
return arr[i .. j];
}
or
T[] foo(U)(U arr)
if(is(U : T[]))
{
T[] retval = arr;
...
return retval[i .. j];
}
then the implicit conversion is done inside the function. And because static
arrays are value types, the slice that's returned is a slice of local memory
and is therefore invalid, causing @safety-related problems.
So, while your particular type might be able to safely convert inside such a
function and still be @safe, that's not true in the general case. As such,
templated code that wants to accept implicit conversions to dynamic arrays
really needs to be templated on the element type and not the whole type.
e.g.
T[] foo(T)(T[] arr)
{
...
return arr[i .. j];
}
can @safely return a slice, because the implicit conversion was forced at
the call site just like it was with the non-templated function.
In general, Phobos only accepts implicit conversions with template
constraints when the function was originally not a template but was later
turned into a template, and the implicit conversion had to be kept in order
to avoid breaking code. And to do that @safely, the conversion to a template
must be done very carefully, and there are actually some cases in Phobos
which still need to be fixed, because it was done incorrectly. All in all,
while it might be annoying sometimes, it's just safer to have templates
require that all conversions be done before making the call rather than
allowing implicit conversions.
- Jonathan M Davis
Re: Nullable!T with T of class type
On Tuesday, June 26, 2018 19:03:20 kdevel via Digitalmars-d-learn wrote:
> On Monday, 25 June 2018 at 22:58:41 UTC, Jonathan M Davis wrote:
> > On Monday, June 25, 2018 19:40:30 kdevel via
> >
> > Digitalmars-d-learn wrote:
> >> R r;
> >>
> >> if (r.s is null)
> >>
> >>throw new Exception ("some error message");
>
> [...]
>
> >> Why can't this programming error be detected at compile time?
> >
> > If you have a function that accepts Nullable!T, when that
> > function is called, how on earth is it going to know whether
> > the argument it received was null at compile time?
>
> That was not the error. The error was that I used is null instead
> of .isNull() which lead to a different Exception (Error).
Well, get checks whether the Nullable isNull, and throws an Error if it is,
which is what you showed in your original post. If you want a Nullable to
have the value of null, then you have to explicitly set it to null. Nullable
really doesn't have anything to do with the null value for pointers or
references beyond the fact that it allows a way to emulate that behavior for
non-nullable types by using a bool.
isNull returns whether the Nullable has been given a value or not, whereas
checking the value with is null means checking whether it has a value and
whether that value is null. If that behavior is not what you want, then you
will have to find a different solution, though honestly, I don't understand
why folks keep trying to put nullable types in Nullable in non-generic code.
- Jonathan M Davis
Re: template recursion
On Tuesday, 26 June 2018 at 20:47:27 UTC, Steven Schveighoffer wrote: Naming the hook for `put` the same thing as the global function was one of the biggest mistakes in the range library. I almost think we would be better off to deprecate that and pick another hook name. If you ever do that it would also be nice to use separate names for "put a single X into Y" and "put everything from container X into Y".
Re: template recursion
On 6/26/18 6:01 AM, ag0aep6g wrote: On line 23, you're apparently trying to call std.range.put (which would in turn call tarr[t].put). But being in a method that is itself called "put", that line is instead interpreted as a recursive call (which fails). To refer to std.range.put, you have to prepend a dot (the "module scope operator"): .put(tarr[t], t); // line 23 https://dlang.org/spec/module.html#module_scope_operators Naming the hook for `put` the same thing as the global function was one of the biggest mistakes in the range library. I almost think we would be better off to deprecate that and pick another hook name. -Steve
Re: Nullable!T with T of class type
On Tuesday, 26 June 2018 at 14:32:59 UTC, Nathan S. wrote: On Monday, 25 June 2018 at 19:40:30 UTC, kdevel wrote: Is it possible to "lower" the Nullable operations if T is a class type such that there is only one level of nullification? Yes: https://run.dlang.io/is/hPxbyf template Nullable(S) [...] Works nicely. Thanks!
Re: Nullable!T with T of class type
On Monday, 25 June 2018 at 22:58:41 UTC, Jonathan M Davis wrote:
On Monday, June 25, 2018 19:40:30 kdevel via
Digitalmars-d-learn wrote:
R r;
if (r.s is null)
throw new Exception ("some error message");
[...]
Why can't this programming error be detected at compile time?
If you have a function that accepts Nullable!T, when that
function is called, how on earth is it going to know whether
the argument it received was null at compile time?
That was not the error. The error was that I used is null instead
of .isNull() which lead to a different Exception (Error).
[...]
If you really don't want the extra bool, then just don't use
Nullable. Class references are already naturally nullable.
Sure.
Re: First run after build on Windows is slow
On Tuesday, 26 June 2018 at 12:58:29 UTC, Adam D. Ruppe wrote: On Tuesday, 26 June 2018 at 12:40:05 UTC, phs wrote: Although, it's a little bit strange because I have never had this issue with my C++ development. The c++ compiler and runtime libraries are common enough that the antivirus realizes it is nothing special, but since D is more obscure it just flags it as abnormal and does further checks. (more obscure C++ compilers can do the same thing). Walter has written Microsoft and they have OK'd it before, but then one side or the other updates and then they are out of whack again :( Yes, the anti-virus situation is really annoying on windows. I couldn't install dmd 2.080 on the work PC as the AV always quarantained some of the installed tools which made the install routine fail. The blame lies on our work PC's which are incredibly misconfigured and limited (proxy that Microsoft VS installer can not overcome even if any other program can, extra small system SSD, eager anti-virus that cannot be instructed of anything, profiles with read/write desktop but no delete (this means that a shortcut can be copied on the desktop but can never be removed), etc. etc.) Just had to vent my frustration. I love D but the elements are against me to be able to enjoy it to the fullest...
Re: How do I call this tamplte function?
On 06/26/2018 10:37 AM, Rib wrote:
to get get() from std.net.curl return a ubyte[] and use my http
instance, all those failed:
string link = "http://...";;
auto client = HTTP();
// set some client attributes...
auto fileContents = get!(AutoProtocol, ubyte)(link, client);
auto fileContents = get!(ubyte)(link, client);
auto fileContents = get!(client, ubyte)(link, client);
I still didn't "get" D templates.
This worked for me:
import std.net.curl;
import std.stdio;
import std.functional;
void myHeaderReceivingFunction(const(char[]) key, const(char[]) value) {
writefln("Received header: %s = %s", key, value);
}
size_t myDataReceivingFunction(ubyte[] data) {
writefln("Received data; first part: %s", data[0..10]);
return data.length;
}
void main() {
auto client = HTTP("http://dlang.org";);
// If you don't have an actual delegate, you can use
std.functional.toDelegate:
client.onReceiveHeader = (&myHeaderReceivingFunction).toDelegate;
// ... or you can create a delegate with a lambda on the fly:
client.onReceive = (ubyte[] data) { return
myDataReceivingFunction(data); };
client.perform();
}
Ali
How do I call this tamplte function?
to get get() from std.net.curl return a ubyte[] and use my http instance, all those failed: string link = "http://...";; auto client = HTTP(); // set some client attributes... auto fileContents = get!(AutoProtocol, ubyte)(link, client); auto fileContents = get!(ubyte)(link, client); auto fileContents = get!(client, ubyte)(link, client); I still didn't "get" D templates.
CustomString and string constraints
Is possible to make a Custom Struct String work for D string
constraints?
eg:
struct MyString
{
char[] arr;
alias arr this;
}
void getString( char[] str ){}
MyString().split(";"); //oops, type mismatch
getString( MyString() ); //fine, implicit conversion
isSomeString!(char[]).writeln; //true
isSomeString!(MyString).writeln; //false
Re: Nullable!T with T of class type
On Monday, 25 June 2018 at 22:58:41 UTC, Jonathan M Davis wrote: Java does try to force you to initialize stuff (resulting in annoying false positives at times), but in general, it still can't guarantee when a variable is null or not and is forced to insert runtime null checks. Java can be somewhat clever about this though. Often it just needs to perform a single null check in a method body and thereafter knows the pointer can't be null and elides the check.
Re: Nullable!T with T of class type
On Monday, 25 June 2018 at 19:40:30 UTC, kdevel wrote:
Is it possible
to "lower" the Nullable operations if T is a class type such
that there
is only one level of nullification?
Yes: https://run.dlang.io/is/hPxbyf
template Nullable(S)
{
import std.traits : isPointer, isDynamicArray;
static if (is(S == class) || is(S == interface)
|| is(S == function) || is(S == delegate)
|| isPointer!S || isDynamicArray!S)
{
alias Nullable = S;
}
else
{
static import std.typecons;
alias Nullable = std.typecons.Nullable!S;
}
}
Re: Visual D 0.47.0 released
On 2018-06-24 13:08:53 +, Rainer Schuetze said: a new release of Visual D has just been uploaded. Major changes are * improved Visual C++ project integration: better dependencies, automatic libraries, name demangling * new project wizard * mago debugger: show vtable, dynamic type of interfaces, symbol names of pointer address As soon as I use the Mago debugger, it's impossible to start a debugging session. Any idea how to track down such a problem? -- Robert M. Münch http://www.saphirion.com smarter | better | faster
Re: alias symbol name
On Tuesday, 26 June 2018 at 12:19:16 UTC, Jonathan M Davis wrote: On Tuesday, June 26, 2018 11:28:11 Radu via Digitalmars-d-learn wrote: > [...] Ha! :) yeah I was pretty sure this will not work. I'm looking to generate some custom wrappers and knowing when something is really `size_t` is important, I have a backup plan, but having a compiler trait to get an alias symbol name would be great. Maybe this is worthy an enhancement request? Feel free. I have no idea how likely it is to ever be implemented. However, if your custom wrappers are generated at compilation time rather than generated as files to be compiled later, then it's unnecessary to know whether an alias was used, since then you'd just use the exact type being used for that particular compilation. - Jonathan M Davis Code generation is at compile time and the target is C code, so it is important to keep the type `size_t` rather than `uint` or `ulong` for obvious reasons. I will submit and issue for a new trait.
Re: First run after build on Windows is slow
On Tuesday, 26 June 2018 at 12:40:05 UTC, phs wrote: Although, it's a little bit strange because I have never had this issue with my C++ development. The c++ compiler and runtime libraries are common enough that the antivirus realizes it is nothing special, but since D is more obscure it just flags it as abnormal and does further checks. (more obscure C++ compilers can do the same thing). Walter has written Microsoft and they have OK'd it before, but then one side or the other updates and then they are out of whack again :(
Re: First run after build on Windows is slow
On Tuesday, 26 June 2018 at 12:26:45 UTC, rikki cattermole wrote: On 27/06/2018 12:25 AM, phs wrote: Hello. I've made a simple hello world program using dub and dmd for Windows. Everything works well, except that every first run after each rebuild takes around 3 seconds just to start up. Is it normal at all? Its normal if you don't add an exclusion for that directory in your anti-virus. Thank you for the hint. Disabling the Windows Defender helped to resolve this issue. Although, it's a little bit strange because I have never had this issue with my C++ development.
First run after build on Windows is slow
Hello. I've made a simple hello world program using dub and dmd for Windows. Everything works well, except that every first run after each rebuild takes around 3 seconds just to start up. Is it normal at all?
Re: First run after build on Windows is slow
On 27/06/2018 12:25 AM, phs wrote: Hello. I've made a simple hello world program using dub and dmd for Windows. Everything works well, except that every first run after each rebuild takes around 3 seconds just to start up. Is it normal at all? Its normal if you don't add an exclusion for that directory in your anti-virus.
Re: alias symbol name
On Tuesday, June 26, 2018 11:28:11 Radu via Digitalmars-d-learn wrote: > > I'm pretty sure that that's impossible. As I understand it, the > > compiler basically just replaces aliases with what they refer > > to and doesn't care what the original type was. And they > > _definitely_ don't affect mangling. If you're looking to treat > > an alias as anything different from what it refers to, you're > > going to be disappointed. > > > > - Jonathan M Davis > > Ha! :) yeah I was pretty sure this will not work. > > I'm looking to generate some custom wrappers and knowing when > something is really `size_t` is important, I have a backup plan, > but having a compiler trait to get an alias symbol name would be > great. Maybe this is worthy an enhancement request? Feel free. I have no idea how likely it is to ever be implemented. However, if your custom wrappers are generated at compilation time rather than generated as files to be compiled later, then it's unnecessary to know whether an alias was used, since then you'd just use the exact type being used for that particular compilation. - Jonathan M Davis
Re: alias symbol name
On Tuesday, 26 June 2018 at 10:19:44 UTC, Jonathan M Davis wrote:
On Tuesday, June 26, 2018 09:47:44 Radu via Digitalmars-d-learn
wrote:
On Tuesday, 26 June 2018 at 09:24:15 UTC, Stefan Koch wrote:
> On Tuesday, 26 June 2018 at 09:14:11 UTC, Radu wrote:
>> Consider this https://run.dlang.io/is/HyY2qG
>>
>> ---
>> void main()
>> {
>>
>> import std.traits;
>> size_t s;
>>
>> pragma(msg, typeof(s).stringof);
>> pragma(msg, mangledName!(typeof(s)));
>> pragma(msg, mangledName!s);
>>
>> }
>> ---
>>
>> It outputs:
>> ---
>> ulong
>> m
>> _D9onlineapp4mainFZ1sm
>> ---
>>
>> I'm looking for a way to get the `s` type symbol name
>> (size_t)
>> not whatever the alias is pointing to (ulong in this case).
>>
>> Is there a way to obtain the alias symbol name?
>
> __traits(identifier, sym);
Him, that will print the symbol name, in my case `s`.
To cut to chase - I'm looking something that will print
`size_t` for the symbol `s`.
I'm pretty sure that that's impossible. As I understand it, the
compiler basically just replaces aliases with what they refer
to and doesn't care what the original type was. And they
_definitely_ don't affect mangling. If you're looking to treat
an alias as anything different from what it refers to, you're
going to be disappointed.
- Jonathan M Davis
Ha! :) yeah I was pretty sure this will not work.
I'm looking to generate some custom wrappers and knowing when
something is really `size_t` is important, I have a backup plan,
but having a compiler trait to get an alias symbol name would be
great. Maybe this is worthy an enhancement request?
Re: alias symbol name
On Tuesday, June 26, 2018 09:47:44 Radu via Digitalmars-d-learn wrote:
> On Tuesday, 26 June 2018 at 09:24:15 UTC, Stefan Koch wrote:
> > On Tuesday, 26 June 2018 at 09:14:11 UTC, Radu wrote:
> >> Consider this https://run.dlang.io/is/HyY2qG
> >>
> >> ---
> >> void main()
> >> {
> >>
> >> import std.traits;
> >> size_t s;
> >>
> >> pragma(msg, typeof(s).stringof);
> >> pragma(msg, mangledName!(typeof(s)));
> >> pragma(msg, mangledName!s);
> >>
> >> }
> >> ---
> >>
> >> It outputs:
> >> ---
> >> ulong
> >> m
> >> _D9onlineapp4mainFZ1sm
> >> ---
> >>
> >> I'm looking for a way to get the `s` type symbol name (size_t)
> >> not whatever the alias is pointing to (ulong in this case).
> >>
> >> Is there a way to obtain the alias symbol name?
> >
> > __traits(identifier, sym);
>
> Him, that will print the symbol name, in my case `s`.
>
> To cut to chase - I'm looking something that will print `size_t`
> for the symbol `s`.
I'm pretty sure that that's impossible. As I understand it, the compiler
basically just replaces aliases with what they refer to and doesn't care
what the original type was. And they _definitely_ don't affect mangling. If
you're looking to treat an alias as anything different from what it refers
to, you're going to be disappointed.
- Jonathan M Davis
Re: template recursion
On Tuesday, 26 June 2018 at 10:01:06 UTC, ag0aep6g wrote: On line 23, you're apparently trying to call std.range.put (which would in turn call tarr[t].put). But being in a method that is itself called "put", that line is instead interpreted as a recursive call (which fails). To refer to std.range.put, you have to prepend a dot (the "module scope operator"): .put(tarr[t], t); // line 23 https://dlang.org/spec/module.html#module_scope_operators Ah... that's cool :) Thanks a lot!
Re: template recursion
On 06/26/2018 11:35 AM, Alex wrote:
´´´
import std.range;
void main()
{
T.member.tarr.length = 42;
//put(T.member, 4); // line 6
T.member.put(4); // line 7
}
struct T
{
void put(Type)(Type t){} // line 13
static B member;
}
struct B
{
T[] tarr;
void put(Type)(Type t)
{
put(tarr[t], t); // line 23
}
}
´´´
Line 7 complains about:
template app.B.put cannot deduce function from argument types !()(T, int)
So, I see, that the compiler tries to use the same put function in line
23, as in line 7 and fails. Instead of this, I want to use the one in
line 13.
But I don't see any mistake at line 23...
On line 23, you're apparently trying to call std.range.put (which would
in turn call tarr[t].put). But being in a method that is itself called
"put", that line is instead interpreted as a recursive call (which
fails). To refer to std.range.put, you have to prepend a dot (the
"module scope operator"):
.put(tarr[t], t); // line 23
https://dlang.org/spec/module.html#module_scope_operators
Re: alias symbol name
On Tuesday, 26 June 2018 at 09:24:15 UTC, Stefan Koch wrote:
On Tuesday, 26 June 2018 at 09:14:11 UTC, Radu wrote:
Consider this https://run.dlang.io/is/HyY2qG
---
void main()
{
import std.traits;
size_t s;
pragma(msg, typeof(s).stringof);
pragma(msg, mangledName!(typeof(s)));
pragma(msg, mangledName!s);
}
---
It outputs:
---
ulong
m
_D9onlineapp4mainFZ1sm
---
I'm looking for a way to get the `s` type symbol name (size_t)
not whatever the alias is pointing to (ulong in this case).
Is there a way to obtain the alias symbol name?
__traits(identifier, sym);
Him, that will print the symbol name, in my case `s`.
To cut to chase - I'm looking something that will print `size_t`
for the symbol `s`.
template recursion
Hi all,
I have a strange case of template recursion, which I don't know
how to solve:
´´´
import std.range;
void main()
{
T.member.tarr.length = 42;
//put(T.member, 4); // line 6
T.member.put(4); // line 7
}
struct T
{
void put(Type)(Type t){} // line 13
static B member;
}
struct B
{
T[] tarr;
void put(Type)(Type t)
{
put(tarr[t], t); // line 23
}
}
´´´
Line 7 complains about:
template app.B.put cannot deduce function from argument types
!()(T, int)
So, I see, that the compiler tries to use the same put function
in line 23, as in line 7 and fails. Instead of this, I want to
use the one in line 13.
But I don't see any mistake at line 23...
Besides this, as a secondary question:
using line 6 does not yield any helpful debugging message. My put
functions are templates and pretty long and branching, and I'm
trying to debug them somehow, but using idiomatic writing all I
get as a message is something like
"Cannot put a XX into a YY." :(
Re: alias symbol name
On Tuesday, 26 June 2018 at 09:14:11 UTC, Radu wrote:
Consider this https://run.dlang.io/is/HyY2qG
---
void main()
{
import std.traits;
size_t s;
pragma(msg, typeof(s).stringof);
pragma(msg, mangledName!(typeof(s)));
pragma(msg, mangledName!s);
}
---
It outputs:
---
ulong
m
_D9onlineapp4mainFZ1sm
---
I'm looking for a way to get the `s` type symbol name (size_t)
not whatever the alias is pointing to (ulong in this case).
Is there a way to obtain the alias symbol name?
__traits(identifier, sym);
alias symbol name
Consider this https://run.dlang.io/is/HyY2qG
---
void main()
{
import std.traits;
size_t s;
pragma(msg, typeof(s).stringof);
pragma(msg, mangledName!(typeof(s)));
pragma(msg, mangledName!s);
}
---
It outputs:
---
ulong
m
_D9onlineapp4mainFZ1sm
---
I'm looking for a way to get the `s` type symbol name (size_t)
not whatever the alias is pointing to (ulong in this case).
Is there a way to obtain the alias symbol name?
Re: Making sense of recursion
On Monday, 25 June 2018 at 17:45:01 UTC, zbr wrote:
Hi, this question is not specifically D related but I'll just
ask anyway. Consider the following snippet:
void mergeSort(int[] arr, int l, int r)
{
if (l < r) // 1
{
int m = l+(r-l)/2;// 2
mergeSort(arr, l, m); // 3
mergeSort(arr, m+1, r); // 4
merge(arr, l, m, r); // 5
}// 6
} // 7
mergeSort(arr, 0, 4);
When I see this, I visualize the recursion to perform this way:
mergeSort(arr, 0, 4):
0 < 4 ? true: mergeSort(0, 2):
0 < 2 ? true: mergeSort(0, 1):
0 < 1 ? true: mergeSort(0, 0):
0 < 0 ? false: //reach the end of mergeSort /
reach line 6 and then 7
I don't see the computer ever reaching line 4 and 5? Obviously
I'm wrong but where is my mistake?
Thanks.
It's a stack (https://en.wikipedia.org/wiki/Call_stack).
When the program calls a function it is pushed onto the stack. If
that function returns it pops from the stack and the previous
function gets to continue execution from where it stopped before.
