www.digitalmars.com         C & C++   DMDScript  

digitalmars.D.learn - Error reading char in read

reply Jean Cesar <jeanzonta777 yahoo.com.br> writes:
import std.stdio;
import std.string;


auto read(C)(ref C c, char[80] message)
if (isSomeChar!C) {
     writef("\n\t%s: ", message);
     c = strip(readf());
     readf(" %s", &t);
     return c;
}

void main()
{
  char[50] message;
   read(message,"Digite Seu nome: ");
  writeln(message);
}

estou tentando fazer um leitor de vetor de char porem esta dando 
erro
Feb 17 2017
parent reply =?UTF-8?Q?Ali_=c3=87ehreli?= <acehreli yahoo.com> writes:
On 02/17/2017 07:48 AM, Jean Cesar wrote:

 import std.stdio;
 import std.string;


 auto read(C)(ref C c, char[80] message)
 if (isSomeChar!C) {
     writef("\n\t%s: ", message);
     c = strip(readf());
     readf(" %s", &t);
     return c;
 }

 void main()
 {
  char[50] message;
   read(message,"Digite Seu nome: ");
  writeln(message);
 }

 estou tentando fazer um leitor de vetor de char porem esta dando erro


My recommendation is to read some tutorials as there are many large and 
small differences between D, C++, and Java.

Some notes:

- In D, char is UTF-8 code unit. Perhaps you want to read ubyte (or byte)?

- isSomeChar is defined in std.traits. You must import std.traits if you 
want to use isSomeChar:

   https://dlang.org/phobos/std_traits.html

- From the way you call read(), it looks like you want to read a char 
array (vector), not a single char. So, isSomeChar is wrong.

- It is common to use the string type in D. string is an array of 
immutable chars. We can change my read() function to read char[] as well:

- Static arrays like char[50] are different from slices like char[].

The read() examples I had given are incomplete: They should work with 
value types and dynamic strings but not with static arrays. Here is 
another read() that works with char arrays:

import std.stdio;
import std.string;
import std.traits;
import std.range;
import std.algorithm;

auto read(S)(ref S s, string message)
if (isSomeString!S) {
     import std.string : strip;
     writef("%s: ", message);
     s = readln().strip();
     return s;
}

auto read(S)(ref S s, string message)
if (isStaticArray!S &&
     isSomeChar!(ElementType!S)) {

     string tmp;
     read(tmp, message);

     // Clear the array
     s[] = typeof(s[0]).init;

     // Assign without going out of bounds
     const len = min(s.length, tmp.length);
     s[0..len] = tmp[0..len];

     return s;
}

void main()
{
     char[50] message;
     read(message,"Digite Seu nome: ");
     writeln(message);
}

However, you'll see that static arrays may not be suitable for reading 
text, as char[50] will never know how long the actual text is. Here is 
the output:

Digite Seu nome: : Jean
Jean\377\377\377[...]

For that to work, you would have to rely on the old C representation of 
strings with the '\0' character:

     // Assign without going out of bounds
     const len = min(s.length, tmp.length);
     s[0..len] = tmp[0..len];
     const nullChar = min(s.length - 1, len);
     s[nullChar] = '\0';

However, it still doesn't work because char[50] still has 50 characters:

Jean^ \377\377[...]

As you see, you better use 'string' (or its mutable version, char[]) for 
such text.

And again, it will take a long time to go through these basics unless 
you start with some tutorials:

   https://tour.dlang.org/

For strings:

   https://tour.dlang.org/tour/en/basics/alias-strings

Some books:

   https://wiki.dlang.org/Books

Ali
Feb 17 2017
parent reply wiki <jeanzonta777 yahoo.com.br> writes:
On Friday, 17 February 2017 at 18:57:55 UTC, Ali Çehreli wrote:

 On 02/17/2017 07:48 AM, Jean Cesar wrote:

 import std.stdio;
 import std.string;


 auto read(C)(ref C c, char[80] message)
 if (isSomeChar!C) {
     writef("\n\t%s: ", message);
     c = strip(readf());
     readf(" %s", &t);
     return c;
 }

 void main()
 {
  char[50] message;
   read(message,"Digite Seu nome: ");
  writeln(message);
 }

 estou tentando fazer um leitor de vetor de char porem esta 
 dando erro


 My recommendation is to read some tutorials as there are many 
 large and small differences between D, C++, and Java.

 Some notes:

 - In D, char is UTF-8 code unit. Perhaps you want to read ubyte 
 (or byte)?

 - isSomeChar is defined in std.traits. You must import 
 std.traits if you want to use isSomeChar:

   https://dlang.org/phobos/std_traits.html

 - From the way you call read(), it looks like you want to read 
 a char array (vector), not a single char. So, isSomeChar is 
 wrong.

 - It is common to use the string type in D. string is an array 
 of immutable chars. We can change my read() function to read 
 char[] as well:

 - Static arrays like char[50] are different from slices like 
 char[].

 The read() examples I had given are incomplete: They should 
 work with value types and dynamic strings but not with static 
 arrays. Here is another read() that works with char arrays:

 import std.stdio;
 import std.string;
 import std.traits;
 import std.range;
 import std.algorithm;

 auto read(S)(ref S s, string message)
 if (isSomeString!S) {
     import std.string : strip;
     writef("%s: ", message);
     s = readln().strip();
     return s;
 }

 auto read(S)(ref S s, string message)
 if (isStaticArray!S &&
     isSomeChar!(ElementType!S)) {

     string tmp;
     read(tmp, message);

     // Clear the array
     s[] = typeof(s[0]).init;

     // Assign without going out of bounds
     const len = min(s.length, tmp.length);
     s[0..len] = tmp[0..len];

     return s;
 }

 void main()
 {
     char[50] message;
     read(message,"Digite Seu nome: ");
     writeln(message);
 }

 However, you'll see that static arrays may not be suitable for 
 reading text, as char[50] will never know how long the actual 
 text is. Here is the output:

 Digite Seu nome: : Jean
 Jean\377\377\377[...]

 For that to work, you would have to rely on the old C 
 representation of strings with the '\0' character:

     // Assign without going out of bounds
     const len = min(s.length, tmp.length);
     s[0..len] = tmp[0..len];
     const nullChar = min(s.length - 1, len);
     s[nullChar] = '\0';

 However, it still doesn't work because char[50] still has 50 
 characters:

 Jean^ \377\377[...]

 As you see, you better use 'string' (or its mutable version, 
 char[]) for such text.

 And again, it will take a long time to go through these basics 
 unless you start with some tutorials:

   https://tour.dlang.org/

 For strings:

   https://tour.dlang.org/tour/en/basics/alias-strings

 Some books:

   https://wiki.dlang.org/Books

 Ali


So I executed it here anyway but still it presents arbitrary 
characters in the char ..

What I thought was to create a reader where I could receive,
Char, string, int, float, double, real, for my future codes ....

I tried doing this to understand how the char reading was, it is 
preferable to use strings but the language has some specific 
reader for char?

minha frase na captura de char
������������������������
Feb 17 2017
parent reply =?UTF-8?Q?Ali_=c3=87ehreli?= <acehreli yahoo.com> writes:
On 02/17/2017 12:05 PM, wiki wrote:


 So I executed it here anyway but still it presents arbitrary characters
 in the char ..


Right. char[50] is not suitable for user interaction like that. Use 
string, char[], etc.


 What I thought was to create a reader where I could receive,
 Char, string, int, float, double, real, for my future codes ....


That's already available in many different ways: readf, readln, 
formattedRead, etc.


 I tried doing this to understand how the char reading was, it is
 preferable to use strings but the language has some specific reader for
 char?


"%c" can be used to read char. (Although, I still think you want to read 
a string, not a single char.)

import std.stdio;

void main() {
     char c;
     readf("%c", &c);
}


 minha frase na captura de char
������������������������


Sorry, Google Translate did not work for that one. :(

There is a confusion here. You keep saying 'char' but � is not a char 
(i.e. one of the 8-bit types). It's the Unicode character "U+FFFD 
REPLACEMENT CHARACTER", which is represented by 2 chars in D. char is a 
UTF-8 code unit, not a "character" in the sense that I think you're 
using it.

Ali
Feb 17 2017
parent reply ag0aep6g <anonymous example.com> writes:
On 02/17/2017 09:24 PM, Ali Çehreli wrote:

 It's the Unicode character "U+FFFD
 REPLACEMENT CHARACTER", which is represented by 2 chars in D.


It takes 3 `char`s to represent U+FFFD:

void main()
{
     import std.stdio;
     writeln("\uFFFD".length); /* prints "3" */
}
Feb 17 2017
parent Jean Cesar <jeanzonta777 yahoo.com.br> writes:
On Friday, 17 February 2017 at 21:34:16 UTC, ag0aep6g wrote:

 On 02/17/2017 09:24 PM, Ali Çehreli wrote:

 It's the Unicode character "U+FFFD
 REPLACEMENT CHARACTER", which is represented by 2 chars in D.


 It takes 3 `char`s to represent U+FFFD:

 void main()
 {
     import std.stdio;
     writeln("\uFFFD".length); /* prints "3" */
 }


Yes I also think about the possibility of the user to use the 
char definition to read a sequence of characters, but calm ....
Feb 17 2017