Re: probably a trivial question...
On 10/14/22 01:43, WhatMeWorry via Digitalmars-d-learn wrote:
Does D provide any guidance as to what is preferred or are they identical for
all intents and purposes?
You won't see a difference for this specific example since the split function
supports character, string and even range separators. So, use what works best
for your use case.
But here's the difference between them:
Single quotes are for singular characters, 'hello' won't compile while ';' and
'\n' (escaped newline) will.
Double quotes are string literals, i.e. array of characters, which also allow escape
sequences like "\r\n".
Back ticks, as well as r"...", are raw or wysiwyg ("what you see is what you
get") strings, they do not support escape sequences. They are super useful for regex.
import std;
void main() {
writeln("ab\ncd"); // \n is recognized as a newline character
writeln(`ab\ncd`); // `...` and r"..." are equivalent
writeln(r"ab\ncd");
}
will print:
ab
cd
ab\ncd
ab\ncd
More info here, if you are interested:
https://dlang.org/spec/lex.html#string_literals
Re: probably a trivial question...
Changing the order of lines...
On 10/13/22 16:43, WhatMeWorry wrote:
> return s.split(';'); // single quotes
That one is a single character and very lightweigth because it's just an
integral value. You can't put more than one character within single quotes:
';x' // ERROR
> return s.split(";"); // double quotes
That one is a string, which is the equivalent of the following "fat
pointer":
struct Array_ {
size_t length;
char * ptr;
}
For that reason, it can be seen as a little bit more costly. 'length'
happens to be 1 but you can use multiple characters in a string:
";x" // works
(Aside: There is also a '\0' character sitting next to the ';' in memory
so that the literal can be passed to C functions as-is.)
Double-quoted strings have the property of escaping. For example, "\n"
is not 2 characters but is "the newline character".
> return s.split(`;`); // back ticks
They are strings as well but they don't do escaping: `\n` happens to be
2 characters.
There is also strings that start with q{ and end with }:
auto myString = q{
hello
world
};
And then there is delimited strings that use any delimiter you choose:
auto myString = q"MY_DELIMITER
hello
world
MY_DELIMITER";
Some information here:
http://ddili.org/ders/d.en/literals.html#ix_literals.string%20literal
Ali
probably a trivial question...
I was a little (nicely) surprised that I could use double quotes,
single quotes, or back ticks in the following line of code.
return s.split(";"); // double quotes
or
return s.split(';'); // single quotes
or
return s.split(`;`); // back ticks
Does D provide any guidance as to what is preferred or are they
identical for all intents and purposes?
Re: Probably a trivial question regarding version identifier and unittest
On Tuesday, 12 May 2020 at 02:17:36 UTC, Adam D. Ruppe wrote:
On Tuesday, 12 May 2020 at 01:54:49 UTC, WhatMeWorry wrote:
[...]
The unittest {} block is actually a special syntax for a
function. So the main function in here is a *nested* function
inside the unittest function and thus doesn't count as a
starting point. It is like if you defined
[...]
This is gold! I've been poking around and reading for days, but
you've gotten me further with just a few paragraphs. Cant thank
you enough.
Re: Probably a trivial question regarding version identifier and unittest
On Tuesday, 12 May 2020 at 01:54:49 UTC, WhatMeWorry wrote:
version(demos) unittest
{
import arsd.terminal;
void main()
Shouldn't the version identifier demos and the unittest option
activate the test block and therefore defines main() which then
give the "Start Address"?
The unittest {} block is actually a special syntax for a
function. So the main function in here is a *nested* function
inside the unittest function and thus doesn't count as a starting
point. It is like if you defined
void MyTest() {
void main() {}
}
The main there is a nested local helper function and thus
wouldn't count as a start point either.
Also, what is the isolated main; command right after the main
function?
That's just calling the defined child function so it actually
gets executed. (I didn't put the parens there, but you could:
`main();`, to make it clear it is just calling the function.
You can compile and run the tests btw with the command line:
dmd terminal.d -unittest -version=demos -main
the -main option at the end tells the compiler to add an empty
main() function at top-level for you to satisfy the linker.
The reason I wrote it all this way is for the documentation. Look
here for an example of how it looks when it is rendered:
http://dpldocs.info/experimental-docs/arsd.terminal.html#color
The documentation version there is a complete function my readers
can copy/paste in their own files to use as a starting point.
(the "// exclude from docs" comment is actually recognized by my
doc generator to skip that line, see:
http://dpldocs.info/experimental-docs/adrdox.syntax.html#documented-unittests which lets me tweak the user-visible output while still keeping it machine-checked internally too.)
Now, why is it in a unittest block? Because then the samples are
easier for me to compile and run as a batch to help me make sure
they still work. (This isn't exactly perfect - since they are
still defined in the module, they can see private members and
imports, so it is still possible it will work for me but not for
my readers. But it makes it less likely to it that problem.)
Lastly, why is it in a demos block? That's just because normal
unit tests are not supposed to be interactive and these are
(interactive things make better doc samples). So the version
block makes sure they are not run accidentally like by a user
doing `dub test` at an outer layer. You have to opt into running
these blocks by adding the version flag to the build too.
You can really see this in simpledisplay.d's docs that have full
sample games you can copy/paste and tweak!
http://dpldocs.info/experimental-docs/arsd.simpledisplay.html#pong
source:
http://dpldocs.info/experimental-docs/source/arsd.simpledisplay.d.html#L492
except yikes I forgot to put the version thing there! so someone
dub testing simpledisplay will have to play through a round of
pong and minesweeper to pass the tests :P lol
Re: Probably a trivial question regarding version identifier and unittest
On 5/11/20 9:54 PM, WhatMeWorry wrote:
I'm trying to study Adam Ruppe's terminal.d sub-package and I see the
following code segment:
version(demos) unittest
{
import arsd.terminal;
void main()
{
// . . .
}
main; // exclude from docs
}
Looks like a good baby step to take, so in the command line I use:
C:\dub\path\to\arsdpackage\arsd-official>dmd terminal.d -unittest
-version=demos
OPTLINK (R) for Win32 Release 8.00.17
Copyright (C) Digital Mars 1989-2013 All rights reserved.
http://www.digitalmars.com/ctg/optlink.html
OPTLINK : Warning 134: No Start Address
Shouldn't the version identifier demos and the unittest option activate
the test block and therefore defines main() which then give the "Start
Address"?
That is not a global main, it is inside a unittest block. A unittest
block is actually a function. So the main there is a nested function,
and not the one that D declares as the entry point.
Also, what is the isolated main; command right after the main function?
It's calling the inner function. But I'm sure you would realize that if
you knew that it's not the true main function.
-Steve
Probably a trivial question regarding version identifier and unittest
I'm trying to study Adam Ruppe's terminal.d sub-package and I see
the following code segment:
version(demos) unittest
{
import arsd.terminal;
void main()
{
// . . .
}
main; // exclude from docs
}
Looks like a good baby step to take, so in the command line I use:
C:\dub\path\to\arsdpackage\arsd-official>dmd terminal.d -unittest
-version=demos
OPTLINK (R) for Win32 Release 8.00.17
Copyright (C) Digital Mars 1989-2013 All rights reserved.
http://www.digitalmars.com/ctg/optlink.html
OPTLINK : Warning 134: No Start Address
Shouldn't the version identifier demos and the unittest option
activate the test block and therefore defines main() which then
give the "Start Address"?
Also, what is the isolated main; command right after the main
function?
