Seth Hoenig <seth.a.hoenig gmail.com> writes:

I have these two minimal programs:


import std.string;
void main()
{
    string str = "abc";
    int i = str.count("ab");

}



and:



import std.string;
import std.algorithm;
void main()
{
    string str = "abc";
    int i = str.count("ab");

}



The only difference is line 2, where I import std.algorithm.
The first program compiles fine, but the second program does not compile,
spitting out the error message:

bash-3.2$ dmd -ofdummy dummy.d
/u/sah2659/dmd2/linux/bin/../../src/phobos/std/functional.d(176): Error:
static assert  "Bad binary function q{a == b}. You need to use a valid D
expression using symbols a of type dchar and b of type string."
/u/sah2659/dmd2/linux/bin/../../src/phobos/std/functional.d(179):
instantiated from here: Body!(dchar,string)
/u/sah2659/dmd2/linux/bin/../../src/phobos/std/algorithm.d(3410):
instantiated from here: result!(dchar,string)
dummy.d(7):        instantiated from here: count!("a == b",string,string)


I can't imagine I'm the first person to notice a bug like this, so is there
something I am doing wrong?

"Steven Schveighoffer" <schveiguy yahoo.com> writes:

On Fri, 17 Sep 2010 17:15:31 -0400, Seth Hoenig <seth.a.hoenig gmail.com>  
wrote:

 I have these two minimal programs:


 import std.string;
 void main()
 {
     string str = "abc";
     int i = str.count("ab");

 }



 and:



 import std.string;
 import std.algorithm;
 void main()
 {
     string str = "abc";
     int i = str.count("ab");

 }



 The only difference is line 2, where I import std.algorithm.
 The first program compiles fine, but the second program does not compile,
 spitting out the error message:

 bash-3.2$ dmd -ofdummy dummy.d
 /u/sah2659/dmd2/linux/bin/../../src/phobos/std/functional.d(176): Error:
 static assert  "Bad binary function q{a == b}. You need to use a valid D
 expression using symbols a of type dchar and b of type string."
 /u/sah2659/dmd2/linux/bin/../../src/phobos/std/functional.d(179):
 instantiated from here: Body!(dchar,string)
 /u/sah2659/dmd2/linux/bin/../../src/phobos/std/algorithm.d(3410):
 instantiated from here: result!(dchar,string)
 dummy.d(7):        instantiated from here: count!("a == b",string,string)


 I can't imagine I'm the first person to notice a bug like this, so is  
 there
 something I am doing wrong?

I see two bugs here.  First, this should be an ambiguity error, because  
count matches both std.algorithm.count and std.string.count.  The compiler  
should refuse to compile this I think.

Second, std.algorithm.count looks like this:

size_t count(alias pred = "a == b", Range, E)(Range r, E value) if  
(isInputRange!(Range))

So, E can be any type, completely unrelated to strings, I could do:

count!(string, int[]) which makes no sense.

I think the sig should be

size_t count(alias pred = "a == b", Range, E)(Range r, E value) if  
(isInputRange!(Range) && isImplicitlyConvertable!(E, ElementType!(Range)))

-Steve

Seth Hoenig <seth.a.hoenig gmail.com> writes:

Submitted *Issue 4883 <http://d.puremagic.com/issues/show_bug.cgi?id=4883>


*
On Fri, Sep 17, 2010 at 4:30 PM, Steven Schveighoffer
<schveiguy yahoo.com>wrote:

 On Fri, 17 Sep 2010 17:15:31 -0400, Seth Hoenig <seth.a.hoenig gmail.com>
 wrote:

  I have these two minimal programs:
 import std.string;
 void main()
 {
    string str = "abc";
    int i = str.count("ab");

 }



 and:



 import std.string;
 import std.algorithm;
 void main()
 {
    string str = "abc";
    int i = str.count("ab");

 }



 The only difference is line 2, where I import std.algorithm.
 The first program compiles fine, but the second program does not compile,
 spitting out the error message:

 bash-3.2$ dmd -ofdummy dummy.d
 /u/sah2659/dmd2/linux/bin/../../src/phobos/std/functional.d(176): Error:
 static assert  "Bad binary function q{a == b}. You need to use a valid D
 expression using symbols a of type dchar and b of type string."
 /u/sah2659/dmd2/linux/bin/../../src/phobos/std/functional.d(179):
 instantiated from here: Body!(dchar,string)
 /u/sah2659/dmd2/linux/bin/../../src/phobos/std/algorithm.d(3410):
 instantiated from here: result!(dchar,string)
 dummy.d(7):        instantiated from here: count!("a == b",string,string)


 I can't imagine I'm the first person to notice a bug like this, so is
 there
 something I am doing wrong?

 I see two bugs here.  First, this should be an ambiguity error, because
 count matches both std.algorithm.count and std.string.count.  The compiler
 should refuse to compile this I think.

 Second, std.algorithm.count looks like this:

 size_t count(alias pred = "a == b", Range, E)(Range r, E value) if
 (isInputRange!(Range))

 So, E can be any type, completely unrelated to strings, I could do:

 count!(string, int[]) which makes no sense.

 I think the sig should be

 size_t count(alias pred = "a == b", Range, E)(Range r, E value) if
 (isInputRange!(Range) && isImplicitlyConvertable!(E, ElementType!(Range)))

 -Steve

"Daniel Murphy" <yebblies nospamgmail.com> writes:

"Steven Schveighoffer" <schveiguy yahoo.com> wrote in message 
news:op.vi64pdhveav7ka localhost.localdomain...
 Second, std.algorithm.count looks like this:

 size_t count(alias pred = "a == b", Range, E)(Range r, E value) if 
 (isInputRange!(Range))

 So, E can be any type, completely unrelated to strings, I could do:

 count!(string, int[]) which makes no sense.

 I think the sig should be

 size_t count(alias pred = "a == b", Range, E)(Range r, E value) if 
 (isInputRange!(Range) && isImplicitlyConvertable!(E, ElementType!(Range)))

 -Steve

Except you can call it like this:

string s = "1234";
int[] a = [1, 2, 3];
count!"cast(int)(a - '0') == b.length"(s, a);

Which is perfectly valid. 

"Steven Schveighoffer" <schveiguy yahoo.com> writes:

On Thu, 23 Sep 2010 02:19:55 -0400, Daniel Murphy  
<yebblies nospamgmail.com> wrote:

 "Steven Schveighoffer" <schveiguy yahoo.com> wrote in message
 news:op.vi64pdhveav7ka localhost.localdomain...
 Second, std.algorithm.count looks like this:

 size_t count(alias pred = "a == b", Range, E)(Range r, E value) if
 (isInputRange!(Range))

 So, E can be any type, completely unrelated to strings, I could do:

 count!(string, int[]) which makes no sense.

 I think the sig should be

 size_t count(alias pred = "a == b", Range, E)(Range r, E value) if
 (isInputRange!(Range) && isImplicitlyConvertable!(E,  
 ElementType!(Range)))

 -Steve

 Except you can call it like this:

 string s = "1234";
 int[] a = [1, 2, 3];
 count!"cast(int)(a - '0') == b.length"(s, a);

 Which is perfectly valid.

and insane :)

count(s, cast(char)(a.length + '0'));

-Steve