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digitalmars.D - MAX_CHAR

reply Ben Hanson <Ben.Hanson tfbplc.co.uk> writes:
Hi there,

Can anyone tell me how to get the maximum char value from a string
type? I have a template struct which can take string or wstring and
need to determine the character type from the string type.

Thanks,

Ben
Jun 19 2010
next sibling parent reply Justin Johansson <no spam.com> writes:
Ben Hanson wrote:

 Hi there,
 
 Can anyone tell me how to get the maximum char value from a string
 type? I have a template struct which can take string or wstring and
 need to determine the character type from the string type.
 
 Thanks,
 
 Ben


Ben, are you talking about a lexical value space or a value value space?

It might help you to solicit a better answer if you posted some code 
such as your template struct, and perhaps some method function signatures.

It would also help if you explained what you mean by a character type as 
opposed to a string type.  Are you asking about character encodings such 
as UTF-8 or UTF-16 or US-ASCII for example?  Sorry it is not clear in 
your question.

On the other hand, are you asking a question about the D type system 
because, sorry AFAIK, D does not have a type system that is amenable to 
formal analysis and in this case any answers would be meaningless.


Cheers
Justin Johansson
Jun 19 2010
parent Ben Hanson <Ben.Hanson tfbplc.co.uk> writes:
Hi Justin,

== Quote from Justin Johansson (no spam.com)'s article

 Ben, are you talking about a lexical value space or a value value space?
 It might help you to solicit a better answer if you posted some code
 such as your template struct, and perhaps some method function signatures.
 It would also help if you explained what you mean by a character type as
 opposed to a string type.  Are you asking about character encodings such
 as UTF-8 or UTF-16 or US-ASCII for example?  Sorry it is not clear in
 your question.


I am converting some template C++ code that can work with char or wchar_t. This
code does
not cope with any UTF encoding (I realise this support will ultimately need
adding!)
Apparently in D you can do char.max and all I would like to be able to do is
that but from
a string type. Here is the code I have so far:

module main;

import std.algorithm;
import std.string;

template regex(StringT)
{
struct basic_string_token
{
    bool _negated = false;
    StringT _charset;

    this(const bool negated_, ref StringT charset_)
    {
        _negated = negated_;
        _charset = charset_;
    }

    void remove_duplicates()
    {
        _charset.sort;
        _charset = squeeze(_charset);
    }

    void normalise()
    {
        const size_t max_chars_ = 256; // Needs conditional here based on char
size

        if (_charset.length == max_chars_)
        {
            _negated = !_negated;
            _charset.clear();
        }
        else if (_charset.length > max_chars_ / 2)
        {
            negate();
        }
    }

    void negate()
    {
        _negated = !_negated;
    }
};
}

int main(char[][]argv)
{
    regex!(string).basic_string_token token_;

    token_._charset = "cccbba";
    token_.remove_duplicates();
    return 0;
}

It's in the normalise() routine I would like to know the size of 'char' in.

Thanks,

Ben
Jun 19 2010
prev sibling next sibling parent reply BCS <none anon.com> writes:
Hello Ben,


 Hi there,
 
 Can anyone tell me how to get the maximum char value from a string
 type? I have a template struct which can take string or wstring and
 need to determine the character type from the string type.
 


If you are looking for the X sutch that the following is true (as long as 
fn returns a valid string)

someStringType foo = fn();
assert(foo[rand()%$] <= X);  // check a random position.


Bits out of the following should work:

template Max(T)  { 
  static if(is(T U : U[]))
    const string Max = U.stringof ~ ":" ~ (cast(int)(U.max)).stringof;
  else static assert(false, "oops");
}
import std.stdio;

void main()
{
   writef("%s\n", Max!(string));
   writef("%s\n", Max!(wchar[]));
   writef("%s\n", Max!(dchar[]));
}


Output:
  char:cast(int)'\xff'
  wchar:cast(int)'\U0000ffff'
  dchar:cast(int)'\U0010ffff'


 Thanks,
 
 Ben
 


-- 
... <IXOYE><
Jun 19 2010
parent Ben Hanson <Ben.Hanson tfbplc.co.uk> writes:
Hi BCS,

== Quote from BCS (none anon.com)'s article

 Hello Ben,

 Hi there,

 Can anyone tell me how to get the maximum char value from a string
 type? I have a template struct which can take string or wstring




and

 need to determine the character type from the string type.


 If you are looking for the X sutch that the following is true (as


long as

 fn returns a valid string)
 someStringType foo = fn();
 assert(foo[rand()%$] <= X);  // check a random position.
 Bits out of the following should work:
 template Max(T)  {
   static if(is(T U : U[]))
     const string Max = U.stringof ~ ":" ~ (cast(int)


(U.max)).stringof;

   else static assert(false, "oops");
 }
 import std.stdio;
 void main()
 {
    writef("%s\n", Max!(string));
    writef("%s\n", Max!(wchar[]));
    writef("%s\n", Max!(dchar[]));
 }
 Output:
   char:cast(int)'\xff'
   wchar:cast(int)'\U0000ffff'
   dchar:cast(int)'\U0010ffff'

 Thanks,

 Ben




Yep, that's it!

Thanks a lot

Ben
Jun 19 2010
prev sibling parent reply Andrei Alexandrescu <SeeWebsiteForEmail erdani.org> writes:
On 06/19/2010 08:47 AM, Ben Hanson wrote:

 Hi there,

 Can anyone tell me how to get the maximum char value from a string
 type? I have a template struct which can take string or wstring and
 need to determine the character type from the string type.

 Thanks,

 Ben


Something like:

import std.stdio;

struct Widget(S) {
     enum uint MAX_CHAR = typeof(S.init[0]).max;
}

void main() {
     writeln(Widget!string.MAX_CHAR);
     writeln(Widget!wstring.MAX_CHAR);
     writeln(Widget!dstring.MAX_CHAR);
}

writes

255
65535
1114111


Andrei
Jun 19 2010
parent Ben Hanson <Ben.Hanson tfbplc.co.uk> writes:
Hi Andrei,

== Quote from Andrei Alexandrescu (SeeWebsiteForEmail erdani.org)'s
article

 On 06/19/2010 08:47 AM, Ben Hanson wrote:

 Hi there,

 Can anyone tell me how to get the maximum char value from a string
 type? I have a template struct which can take string or wstring




and

 need to determine the character type from the string type.

 Thanks,

 Ben


 Something like:
 import std.stdio;
 struct Widget(S) {
      enum uint MAX_CHAR = typeof(S.init[0]).max;
 }
 void main() {
      writeln(Widget!string.MAX_CHAR);
      writeln(Widget!wstring.MAX_CHAR);
      writeln(Widget!dstring.MAX_CHAR);
 }
 writes
 255
 65535
 1114111
 Andrei


Great, this is even easier.

Thanks,

Ben
Jun 19 2010