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digitalmars.D.learn - strings

reply rko <rko_member pathlink.com> writes:
hi,

how does one convert strings from 'c' strings to 'd' strings and viceversa?

char[] x;
//'C' 
char y[128];

x = y and y = x?

thanx

rko
May 19 2005
next sibling parent reply "Ben Hinkle" <ben.hinkle gmail.com> writes:
"rko" <rko_member pathlink.com> wrote in message 
news:d6hgl9$19vg$1 digitaldaemon.com...
 hi,

 how does one convert strings from 'c' strings to 'd' strings and 
 viceversa?

 char[] x;
 //'C'
 char y[128];

 x = y and y = x?

 thanx

 rko

I'll answer this in two ways: 1) to convert a D string to a C string call std.string.toStringz. To convert a C string to a D string write y[0 .. strlen(y)]. 2) To copy data from one array to another (eg between char arrays) use y[0 .. numel] = x[0 .. numel]; where numel is the number of elements to copy. The reason to separate converting C/D strings and copying data is that the conversions can share data with the original string and don't necessarily copy data - since the conversion has to do with 0-termination and length computation. Back you your variables, if you have a C string stored in y then to get a D string slice of it run y[0 .. strlen(y)]. If you have a D string in x and you want to copy it to y and make it a C string then run int numel = x.length>127?127:x.length; y[0 .. numel] = x[0 .. numel]; y[numel] = 0;
May 19 2005
parent reply rko <rko_member pathlink.com> writes:
In article <d6i0hv$1nnp$1 digitaldaemon.com>, Ben Hinkle says...
"rko" <rko_member pathlink.com> wrote in message 
news:d6hgl9$19vg$1 digitaldaemon.com...
 hi,

 how does one convert strings from 'c' strings to 'd' strings and 
 viceversa?

 char[] x;
 //'C'
 char y[128];

 x = y and y = x?

 thanx

 rko

I'll answer this in two ways: 1) to convert a D string to a C string call std.string.toStringz. To convert a C string to a D string write y[0 .. strlen(y)]. 2) To copy data from one array to another (eg between char arrays) use y[0 .. numel] = x[0 .. numel]; where numel is the number of elements to copy. The reason to separate converting C/D strings and copying data is that the conversions can share data with the original string and don't necessarily copy data - since the conversion has to do with 0-termination and length computation. Back you your variables, if you have a C string stored in y then to get a D string slice of it run y[0 .. strlen(y)]. If you have a D string in x and you want to copy it to y and make it a C string then run int numel = x.length>127?127:x.length; y[0 .. numel] = x[0 .. numel]; y[numel] = 0;

thanx a million. i know i am a nuisance but how does this work? char[] a; // will get somewhere the content "test string" now i would like to compare such as if(a[0..3] == "test") { .... and that does not work. rko
May 19 2005
parent reply Thomas Kuehne <thomas-dloop kuehne.this-is.spam.cn> writes:
-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1

rko schrieb am Thu, 19 May 2005 12:40:46 +0000 (UTC):
 thanx a million. i know i am a nuisance but how does this work?

 char[] a; // will get somewhere the content "test string"

 now i would like to compare such as 

 if(a[0..3] == "test") { ....

if(a[0..4] == "test") -----BEGIN PGP SIGNATURE----- iD8DBQFCjKZC3w+/yD4P9tIRApSbAKDExZY5iix4zRWHPkmqmkAcTW0KHACfYMVS kNx/e4o77VPTqvnaDZdB59o= =AoDi -----END PGP SIGNATURE-----
May 19 2005
parent reply "Jim H" <jimh nowhere.com> writes:
"Thomas Kuehne" <thomas-dloop kuehne.this-is.spam.cn> wrote in message 
news:d8p9i2.496.thomas-dloop laermschleuder.kuehne.cn...
 if(a[0..3] == "test") { ....

if(a[0..4] == "test")

Yes, as a new user, I thought it was a bit odd that the second index of a slicing index was non-inclusive. It feels like you're indexing off the end of the array. As a C/C++ programmer, I'm fine with thinking in terms of (length-1) for zero-based indexing. It seemed to me that something like a[2..2] should return a one-element array consisting of index 2 rather than an empty array. But I suppose there must be a good rationale for it. Jim
May 23 2005
parent reply Lars Ivar Igesund <larsivar igesund.net> writes:
Jim H wrote:

 
 "Thomas Kuehne" <thomas-dloop kuehne.this-is.spam.cn> wrote in message
 news:d8p9i2.496.thomas-dloop laermschleuder.kuehne.cn...
 if(a[0..3] == "test") { ....

if(a[0..4] == "test")

Yes, as a new user, I thought it was a bit odd that the second index of a slicing index was non-inclusive. It feels like you're indexing off the end of the array. As a C/C++ programmer, I'm fine with thinking in terms of (length-1) for zero-based indexing. It seemed to me that something like a[2..2] should return a one-element array consisting of index 2 rather than an empty array. But I suppose there must be a good rationale for it. Jim

Because you need to be able to specify zero-length slices. If you have an array 'things', where you want to remove element 'ẍ́', where 0 > x > things.length, you can do this: things = things[0..x] ~ things[(x + 1)..things.length]; If [0..0] were the first element, you wouldn't be able to remove it by setting x = 0; Lars Ivar Igesund
May 23 2005
parent reply Derek Parnell <derek psych.ward> writes:
On Mon, 23 May 2005 22:32:08 +0200, Lars Ivar Igesund wrote:

[snip]

 If [0..0] were the first element, you wouldn't be able to remove it by
 setting x = 0;

Just being a bit pedantic, but this only applies to 0-based indexing. For languages that use 1-based indexing, they signal a zero length slice by using the form [x ..x-1], thus in those languages, [1..1] is a one-element slice and [1..0] is a zero length slice. -- Derek Parnell Melbourne, Australia 24/05/2005 7:46:54 AM
May 23 2005
parent reply Lars Ivar Igesund <larsivar igesund.net> writes:
Derek Parnell wrote:

 On Mon, 23 May 2005 22:32:08 +0200, Lars Ivar Igesund wrote:
 
 [snip]
 
 If [0..0] were the first element, you wouldn't be able to remove it by
 setting x = 0;

Just being a bit pedantic, but this only applies to 0-based indexing.

Yes, of course, but we are learning D, here, aren't we? :)
May 24 2005
parent Derek Parnell <derek psych.ward> writes:
On Tue, 24 May 2005 21:09:21 +0200, Lars Ivar Igesund wrote:

 Derek Parnell wrote:
 
 On Mon, 23 May 2005 22:32:08 +0200, Lars Ivar Igesund wrote:
 
 [snip]
 
 If [0..0] were the first element, you wouldn't be able to remove it by
 setting x = 0;

Just being a bit pedantic, but this only applies to 0-based indexing.

Yes, of course, but we are learning D, here, aren't we? :)

Oh yeah, that's right. I keep forgetting even the simplest of things. ;-) -- Derek Parnell Melbourne, Australia 25/05/2005 7:28:48 AM
May 24 2005
prev sibling parent "Andrew Fedoniouk" <news terrainformatica.com> writes:
"rko" <rko_member pathlink.com> wrote in message 
news:d6hgl9$19vg$1 digitaldaemon.com...
 hi,

 how does one convert strings from 'c' strings to 'd' strings and 
 viceversa?

Probably this "zoo" (below) from Harmonia will also help you: module harmomia.utils.string; import std.string; import std.utf; char[] w2a( wchar[] w ) { return toUTF8(w); } char[] w2az( wchar[] w ) { return zstr!(char)(w2a(w)); } char[] wz2a( wchar* w ) { return toUTF8( wz2w(w) ); } char[] wz2az( wchar* w ) { return zstr!(char)(wz2a(w)); } wchar[] a2w( char[] a ) { return toUTF16(a); } wchar[] a2wz( char[] a ) { return zstr!(wchar)(a2w(a)); } wchar[] az2w( char* a ) { return toUTF16( az2a(a) ); } wchar[] az2wz( char* a ) { return zstr!(wchar)(az2w(a)); } wchar[] wz2w( wchar* w ) { return w? w[0..wcslen(w)]: null; } char[] az2a( char* a ) { return a? a[0..strlen(a)]: null; } wchar[] w2wz( wchar[] w ) { return zstr!(wchar)(w); } char[] a2az( char[] a ) { return zstr!(char)(a); } template zstr(CHAR) // in-place zero terminate { CHAR[] zstr(CHAR[] chars) // returns zero terminated string { uint l = chars.length; chars.length = l + 1; chars[l] = 0; chars.length = l; return chars; } }
May 19 2005