## digitalmars.D.learn - Formatting floats and ints

"Darts" <email email.com> writes:
```Hey, I'm just looking for how to turn some numbers into strings
in particualr ways. Specifically, I want to force some ints (and
maybe floats too) to give me a string that consists of exactly
four numbers ( 3005, 0038, 0130, etc ). I'd also like to know how
to format a float to give me only one decimal place. If there are
ways to print out in hex or scientific notation I'd also like to

Sorry if this is a dumb question, I've been looking through the
documentation but I don't know which words apply to this kind of
thing so I'm just not sure if I'm meant to be looking for
conversion, casting, parsing, formatting, trunicating, or
something else .__.; Also is there a way to tell google that I
never mean "golang" when I write "dlang" in a search? I'm this
close to trying Bing just to see if it lets me look for D related
stuff without giving me Go related stuff.
```
Mar 15 2015
"Marc =?UTF-8?B?U2Now7x0eiI=?= <schuetzm gmx.net> writes:
```On Sunday, 15 March 2015 at 15:41:09 UTC, Darts wrote:
Hey, I'm just looking for how to turn some numbers into strings
in particualr ways. Specifically, I want to force some ints
(and maybe floats too) to give me a string that consists of
exactly four numbers ( 3005, 0038, 0130, etc ). I'd also like
to know how to format a float to give me only one decimal
place. If there are ways to print out in hex or scientific
notation I'd also like to know about those too!

import std.stdio;
int x = 42;
writefln("int: %04d", x);
float f = 3.14159;
writefln("float: %.1f", f);
writefln("hex: 0x%08x", x);

If you need to work with the string instead of printing it, use
format():

import std.string : format;
// in not-yet released DMD 2.067
// import std.format : format;
// is also possible
string s = format("%04d", 42);

Here's the explanation of the format strings:
http://dlang.org/phobos/std_format.html

Unfortunately the layout is broken at the moment. Anyway, if
you're unfamiliar with format strings, it may be better to read
one of the existing format string tutorials. Randomly picked one

http://www.cprogramming.com/tutorial/printf-format-strings.html

This one is about C's printf() function, but it's applicable to
D, too, because format strings are almost identical in both
languages.
```
Mar 15 2015
"Darts" <email email.com> writes:
```Thanks! That works perfectly! ;) I'll remember they're called
Format Strings now.

Tangentially related follow up: if I want to cast a string to a
dstring... what are the rules for that? I'm getting an
"object.Error (0): array cast misalignment" message when my
program crashes tring to convert a string to a dstring...
```
Mar 15 2015
"Marc =?UTF-8?B?U2Now7x0eiI=?= <schuetzm gmx.net> writes:
```On Sunday, 15 March 2015 at 17:11:07 UTC, Darts wrote:
Thanks! That works perfectly! ;) I'll remember they're called
Format Strings now.

Tangentially related follow up: if I want to cast a string to a
dstring... what are the rules for that? I'm getting an
"object.Error (0): array cast misalignment" message when my
program crashes tring to convert a string to a dstring...

Casting in this case means reinterpreting the bytes of the
`string` as if it were a `dstring`. For this to work, the string
would have to start at an address and have and address divisible
by 4, which it evidently doesn't.

Anyway, what you want is:

import std.conv : to;
string a = "Hello, world!";
dstring b = a.to!dstring;
```
Mar 15 2015
"Marc =?UTF-8?B?U2Now7x0eiI=?= <schuetzm gmx.net> writes:
```On Sunday, 15 March 2015 at 18:52:29 UTC, Marc Schütz wrote:
On Sunday, 15 March 2015 at 17:11:07 UTC, Darts wrote:
Thanks! That works perfectly! ;) I'll remember they're called
Format Strings now.

Tangentially related follow up: if I want to cast a string to
a dstring... what are the rules for that? I'm getting an
"object.Error (0): array cast misalignment" message when my
program crashes tring to convert a string to a dstring...

Casting in this case means reinterpreting the bytes of the
`string` as if it were a `dstring`. For this to work, the
string would have to start at an address and have and address
divisible by 4, which it evidently doesn't.

Anyway, what you want is:

import std.conv : to;
string a = "Hello, world!";
dstring b = a.to!dstring;