• Jos van Uden (18/18) Jan 15 2012 import std.conv, std.traits, std.ascii;
• bearophile (43/44) Jan 15 2012 Next time I suggest you to use D.learn.
• Andrei Alexandrescu (4/22) Jan 15 2012 Thanks! Well, we don't have yet the javascript that rotates the
• bearophile (5/7) Jan 15 2012 Do you want a large amount of D2 "examples"? Have you seen this page?
• Andrei Alexandrescu (4/11) Jan 15 2012 Great! For now it would be great to have the code that rotates the
• Nick Sabalausky (4/6) Jan 15 2012 Speaking of d-p-l.org contributions, #39 has been merged and could use t...
• Timon Gehr (7/25) Jan 15 2012 Your code will fail for narrow strings containing Unicode.
• Jos van Uden (16/48) Jan 15 2012 Thank you.
• Jos van Uden (15/28) Feb 11 2012 this is better

Jos van Uden <user domain.invalid> writes:

import std.conv, std.traits, std.ascii;

S rot13(S)(S s) if (isSomeString!S) {
     return rot(s, 13);
}

S rot(S)(S s, int key) if (isSomeString!S) {
     dchar[] r = new dchar[s.length];

     foreach (i, dchar c; s) {
         if (isLower(c))
             c = ((c - 'a' + key) % 26 + 'a');
         else if (isUpper(c))
             c = ((c - 'A' + key) % 26 + 'A');
         r[i] = c;
     }
     return to!S(r);
}


---

still learning this stuff, feel free to correct or improve

Jos

bearophile <bearophileHUGS lycos.com> writes:

Jos van Uden:

 still learning this stuff, feel free to correct or improve

Next time I suggest you to use D.learn.

This is a first draft with some changes:

import std.traits, std.string, std.ascii, std.conv, std.range;

// is partial application better here?
dstring rot13(C)(immutable(C[]) s) pure /*nothrow*/
if (isSomeChar!C) {
    return rot(s, 13);
}

// or maybe just use in int key=13 as default argument
// is it right to use a signed int for key?
dstring rot(C)(immutable(C[]) s, in int key) pure /*nothrow*/
if (isSomeChar!C)
in {
    // preconditions here...
    // only ASCII input chars?
    // Are std.ascii.isUpper / isLower working with UTF?
} out(result) {
    // don't use .length here unless the input is verified to contain
    // no past ASCII chars
    assert(walkLength(s) == walkLength(result));
} body {
    auto result = new dchar[s.length];

    foreach (i, dchar c; s) { // not nothrow
        // reassigning c here is not nice
        if (isLower(c))
            result[i] = ((c - 'a' + key) % 26 + 'a');
        else if (isUpper(c))
            result[i] = ((c - 'A' + key) % 26 + 'A');
    }

     return result; // implicit cast, but only dstring output.
     // Otherwise allocate a result with alloca() and copy
     // it at the end with to!S(result)
} unittest {
    // unit tests here...
}

void main() {
    import std.stdio;
    writeln(rot13("hello"));
}

Your little program also shows some of the current D2 problems. You need care
to catch a function signature like that that allows implicit cast of the result
of the pure function.

Bye,
bearophile

Andrei Alexandrescu <SeeWebsiteForEmail erdani.org> writes:

On 1/15/12 8:23 AM, Jos van Uden wrote:
 import std.conv, std.traits, std.ascii;

 S rot13(S)(S s) if (isSomeString!S) {
 return rot(s, 13);
 }

 S rot(S)(S s, int key) if (isSomeString!S) {
 dchar[] r = new dchar[s.length];

 foreach (i, dchar c; s) {
 if (isLower(c))
 c = ((c - 'a' + key) % 26 + 'a');
 else if (isUpper(c))
 c = ((c - 'A' + key) % 26 + 'A');
 r[i] = c;
 }
 return to!S(r);
 }


 ---

 still learning this stuff, feel free to correct or improve

 Jos

Thanks! Well, we don't have yet the javascript that rotates the 
examples. Would anyone be interested to work on that?

Andrei

bearophile <bearophileHUGS lycos.com> writes:

Andrei Alexandrescu:

 Thanks! Well, we don't have yet the javascript that rotates the 
 examples. Would anyone be interested to work on that?

Do you want a large amount of D2 "examples"? Have you seen this page?
http://rosettacode.org/wiki/Category:D

Bye,
bearophile

Andrei Alexandrescu <SeeWebsiteForEmail erdani.org> writes:

On 1/15/12 9:26 AM, bearophile wrote:
 Andrei Alexandrescu:

 Thanks! Well, we don't have yet the javascript that rotates the
 examples. Would anyone be interested to work on that?

 Do you want a large amount of D2 "examples"? Have you seen this page?
 http://rosettacode.org/wiki/Category:D

 Bye,
 bearophile

Great! For now it would be great to have the code that rotates the 
script on our homepage.

Andrei

"Nick Sabalausky" <a a.a> writes:

"Andrei Alexandrescu" <SeeWebsiteForEmail erdani.org> wrote in message 
news:jeuqua$1gfg$3 digitalmars.com...
 Thanks! Well, we don't have yet the javascript that rotates the examples. 
 Would anyone be interested to work on that?


put up on the site. Not to nag about it, just a friendly heads-up.

Timon Gehr <timon.gehr gmx.ch> writes:

On 01/15/2012 03:23 PM, Jos van Uden wrote:
 import std.conv, std.traits, std.ascii;

 S rot13(S)(S s) if (isSomeString!S) {
 return rot(s, 13);
 }

 S rot(S)(S s, int key) if (isSomeString!S) {
 dchar[] r = new dchar[s.length];

 foreach (i, dchar c; s) {
 if (isLower(c))
 c = ((c - 'a' + key) % 26 + 'a');
 else if (isUpper(c))
 c = ((c - 'A' + key) % 26 + 'A');
 r[i] = c;
 }
 return to!S(r);
 }


 ---

 still learning this stuff, feel free to correct or improve

 Jos

Your code will fail for narrow strings containing Unicode.
dchar[] r = new dchar[s.length]; // creates a new dchar[] with as many 
elements as there are code units in the input string

You can use std.range.walkLength to get the number of code points.

Furthermore, that line mentions the type twice.

auto r = new dchar[s.walkLength()];

Jos van Uden <user domain.invalid> writes:

On 15-1-2012 17:26, Timon Gehr wrote:
 On 01/15/2012 03:23 PM, Jos van Uden wrote:
 import std.conv, std.traits, std.ascii;

 S rot13(S)(S s) if (isSomeString!S) {
 return rot(s, 13);
 }

 S rot(S)(S s, int key) if (isSomeString!S) {
 dchar[] r = new dchar[s.length];

 foreach (i, dchar c; s) {
 if (isLower(c))
 c = ((c - 'a' + key) % 26 + 'a');
 else if (isUpper(c))
 c = ((c - 'A' + key) % 26 + 'A');
 r[i] = c;
 }
 return to!S(r);
 }


 ---

 still learning this stuff, feel free to correct or improve

 Jos

 Your code will fail for narrow strings containing Unicode.
 dchar[] r = new dchar[s.length]; // creates a new dchar[] with as many
 elements as there are code units in the input string

 You can use std.range.walkLength to get the number of code points.

 Furthermore, that line mentions the type twice.

 auto r = new dchar[s.walkLength()];

Thank you.

---

S rot13(S)(S s) if (isSomeString!S) {
     return rot(s, 13);
}

S rot(S)(S s, int key) if (isSomeString!S) {
     auto r = new dchar[s.walkLength()];

     foreach (i, dchar c; s) {
         if (isLower(c))
             r[i] = ((c - 'a' + key) % 26 + 'a');
         else if (isUpper(c))
             r[i] = ((c - 'A' + key) % 26 + 'A');
     }
     return to!S(r);
}

Jos van Uden <user domain.invalid> writes:

 S rot13(S)(S s) if (isSomeString!S) {
 return rot(s, 13);
 }

 S rot(S)(S s, int key) if (isSomeString!S) {
 auto r = new dchar[s.walkLength()];

 foreach (i, dchar c; s) {
 if (isLower(c))
 r[i] = ((c - 'a' + key) % 26 + 'a');
 else if (isUpper(c))
 r[i] = ((c - 'A' + key) % 26 + 'A');
 }
 return to!S(r);
 }

this is better

S rot13(S)(in S s) if (isSomeString!S) {
     return rot(s, 13);
}

S rot(S)(in S s, in int key) if (isSomeString!S) {
     auto r = new dchar[s.walkLength];

     foreach (i, dchar c; s) {
         if (std.ascii.isLower(c))
             c = ((c - 'a' + key) % 26 + 'a');
         else if (std.ascii.isUpper(c))
             c = ((c - 'A' + key) % 26 + 'A');
         r[i] = c;
     }
     return to!S(r);
}