Re: std.format range with compound format specifiers?
On 11/19/19 7:28 PM, Petar Kirov [ZombineDev] wrote:
In cases where I have some aggregate data, but I don't feel like writing
a custom toString method, I often wrap the data in a Tuple and use its
[1] %(inner%) or %(inner%|sep%) format specifiers. Here's an example:
import std;
void main()
{
{
alias NV = tuple;
auto arr = [NV("Steve", 1), NV("George", 500), NV("Adam", -5)];
writefln("%(%(%s: %s%), %)", arr);
}
{
static struct NV
{
string name;
int value;
}
auto arr = [NV("Steve", 1), NV("George", 500), NV("Adam", -5)];
writefln("%(%(%s: %s%), %)", arr.map!(obj => obj.tupleof.tuple));
}
}
In this case, from outside to inside, I am first formatting the range
and then for each tuple I am formatting its fields one by one.
Sweet! This is exactly what I was looking for.
If for exmaple I want to format a tuple with 3 double, each one of them
with a different number of digits after the decimal point, I could do:
"%(%.1f %.2f %.3f%)".writefln(tuple(1.5, 1.25, 1.125));
Nice. I think this should work well for me.
I think we should extend std.format with support for using the same
tuple formatting specifier as std.typecons.Tuple, but for structs and
possibly classes, as I find it quite useful.
Yes. At least the mechanism you describe should be pasted into
formattedWrite's spec as I had no idea about it, and I would not think
to look at tuple docs for the answer.
A format spec that indicates formattedWrite should use tupleof and treat
it the same would be nice instead of having to do map.tupleof.tuple.
-Steve
Re: std.format range with compound format specifiers?
On Tuesday, 19 November 2019 at 21:50:08 UTC, Steven
Schveighoffer wrote:
I know I can format a range with a format string that contains
%(%s, %). And this results in a nice comma separated list for
each item.
But what about an item that has a not-so-cookie-cutter format?
Like for instance a name/value field:
struct NV
{
string name;
int value;
}
If I want to print one of these, I can do:
format("%s: %s", nv.name, nv.value);
If I wanted to print a range of these, let's say:
auto arr = [NV("Steve", 1), NV("George", 500), NV("Adam", -5)];
How can I have it come out like:
Steve: 1, George: 500, Adam: -5
Do I have to define a toString method in the NV struct? Is
there not another way besides doing this?
-Steve
In cases where I have some aggregate data, but I don't feel like
writing a custom toString method, I often wrap the data in a
Tuple and use its [1] %(inner%) or %(inner%|sep%) format
specifiers. Here's an example:
import std;
void main()
{
{
alias NV = tuple;
auto arr = [NV("Steve", 1), NV("George", 500), NV("Adam",
-5)];
writefln("%(%(%s: %s%), %)", arr);
}
{
static struct NV
{
string name;
int value;
}
auto arr = [NV("Steve", 1), NV("George", 500), NV("Adam",
-5)];
writefln("%(%(%s: %s%), %)", arr.map!(obj =>
obj.tupleof.tuple));
}
}
In this case, from outside to inside, I am first formatting the
range and then for each tuple I am formatting its fields one by
one.
If for exmaple I want to format a tuple with 3 double, each one
of them with a different number of digits after the decimal
point, I could do:
"%(%.1f %.2f %.3f%)".writefln(tuple(1.5, 1.25, 1.125));
If on the other hand I want to format all tuple elements the
same, I would use this scheme:
"%(%.1f%| %)".writefln(tuple(1.5, 1.25, 1.125));
I think we should extend std.format with support for using the
same tuple formatting specifier as std.typecons.Tuple, but for
structs and possibly classes, as I find it quite useful.
[1]: https://dlang.org/phobos/std_typecons#.Tuple.toString
std.format range with compound format specifiers?
I know I can format a range with a format string that contains %(%s, %).
And this results in a nice comma separated list for each item.
But what about an item that has a not-so-cookie-cutter format? Like for
instance a name/value field:
struct NV
{
string name;
int value;
}
If I want to print one of these, I can do:
format("%s: %s", nv.name, nv.value);
If I wanted to print a range of these, let's say:
auto arr = [NV("Steve", 1), NV("George", 500), NV("Adam", -5)];
How can I have it come out like:
Steve: 1, George: 500, Adam: -5
Do I have to define a toString method in the NV struct? Is there not
another way besides doing this?
-Steve
