• Andrei Alexandrescu (17/17) Jan 16 2011 I just added a useful function to Phobos: findSkip. Refer to
• =?UTF-8?B?QWxpIMOHZWhyZWxp?= (7/35) Jan 17 2011 I am not sure where findSkip is useful but can we assume that the caller...
• Andrei Alexandrescu (7/41) Jan 17 2011 findSkip is useful in parsing. One simple case in which it was useful
• Graham St Jack (4/49) Jan 17 2011 --

Andrei Alexandrescu <SeeWebsiteForEmail erdani.org> writes:

I just added a useful function to Phobos: findSkip. Refer to

http://d-programming-language.org/cutting-edge/phobos/std_algorithm.html#findSkip

and

http://www.dsource.org/projects/phobos/changeset/2339

I'm unsure about the signature. Currently the function returns 
Tuple!(R1, "balance", bool, "found"), i.e. the balance of the range 
being searched and a Boolean telling whether or not the other range was 
found. The Boolean is necessary because returning an empty range is 
ambiguous - did you find the needle at the very end of the haystack, or 
not at all?

I think a signature that's easier to use is:

bool findSkip(alias pred = "a == b", R1, R2)(ref R1 haystack, R2 needle);

i.e. the haystack is passed by reference and modified if the find was 
successful. This is in keep with skipOver's signature, but not in keep 
with find's signature.

Opinions?


Andrei

=?UTF-8?B?QWxpIMOHZWhyZWxp?= <acehreli yahoo.com> writes:

Andrei Alexandrescu wrote:
 I just added a useful function to Phobos: findSkip. Refer to
 
 http://d-programming-language.org/cutting-edge/phobos/std_alg
rithm.html#findSkip 
 
 
 and
 
 http://www.dsource.org/projects/phobos/changeset/2339
 
 I'm unsure about the signature. Currently the function returns 
 Tuple!(R1, "balance", bool, "found"), i.e. the balance of the range 
 being searched and a Boolean telling whether or not the other range was 
 found. The Boolean is necessary because returning an empty range is 
 ambiguous - did you find the needle at the very end of the haystack, or 
 not at all?
 
 I think a signature that's easier to use is:
 
 bool findSkip(alias pred = "a == b", R1, R2)(ref R1 haystack, R2 needle);
 
 i.e. the haystack is passed by reference and modified if the find was 
 successful. This is in keep with skipOver's signature, but not in keep 
 with find's signature.
 
 Opinions?
 
 
 Andrei

I am not sure where findSkip is useful but can we assume that the caller 
is not interested in whether it was found or not?

If the callers are interested, they should have the option of calling 
find and skip separately. If they are always interested, then find and 
skip should not be merged together.

Ali

Andrei Alexandrescu <SeeWebsiteForEmail erdani.org> writes:

On 1/17/11 3:21 PM, Ali Çehreli wrote:
 Andrei Alexandrescu wrote:
 I just added a useful function to Phobos: findSkip. Refer to

 http://d-programming-language.org/cutting-edge/phobos/std_algorithm.html#findSkip


 and

 http://www.dsource.org/projects/phobos/changeset/2339

 I'm unsure about the signature. Currently the function returns
 Tuple!(R1, "balance", bool, "found"), i.e. the balance of the range
 being searched and a Boolean telling whether or not the other range
 was found. The Boolean is necessary because returning an empty range
 is ambiguous - did you find the needle at the very end of the
 haystack, or not at all?

 I think a signature that's easier to use is:

 bool findSkip(alias pred = "a == b", R1, R2)(ref R1 haystack, R2 needle);

 i.e. the haystack is passed by reference and modified if the find was
 successful. This is in keep with skipOver's signature, but not in keep
 with find's signature.

 Opinions?


 Andrei

 I am not sure where findSkip is useful but can we assume that the caller
 is not interested in whether it was found or not?

 If the callers are interested, they should have the option of calling
 find and skip separately. If they are always interested, then find and
 skip should not be merged together.

findSkip is useful in parsing. One simple case in which it was useful 
was count() that counts how many times a forward range occurs in 
another. You can't do that with find(). (Try it!)

I made the executive decision to pass by reference and return a bool.

http://d-programming-language.org/cutting-edge/phobos/std_algorithm.html#findSkip


Andrei

Graham St Jack <Graham.StJack internode.on.net> writes:

On 18/01/11 08:04, Andrei Alexandrescu wrote:
 On 1/17/11 3:21 PM, Ali Çehreli wrote:
 Andrei Alexandrescu wrote:
 I just added a useful function to Phobos: findSkip. Refer to

 http://d-programming-language.org/cutting-edge/phobos/std_alg
rithm.html#findSkip 



 and

 http://www.dsource.org/projects/phobos/changeset/2339

 I'm unsure about the signature. Currently the function returns
 Tuple!(R1, "balance", bool, "found"), i.e. the balance of the range
 being searched and a Boolean telling whether or not the other range
 was found. The Boolean is necessary because returning an empty range
 is ambiguous - did you find the needle at the very end of the
 haystack, or not at all?

 I think a signature that's easier to use is:

 bool findSkip(alias pred = "a == b", R1, R2)(ref R1 haystack, R2 
 needle);

 i.e. the haystack is passed by reference and modified if the find was
 successful. This is in keep with skipOver's signature, but not in keep
 with find's signature.

 Opinions?


 Andrei

 I am not sure where findSkip is useful but can we assume that the caller
 is not interested in whether it was found or not?

 If the callers are interested, they should have the option of calling
 find and skip separately. If they are always interested, then find and
 skip should not be merged together.

 findSkip is useful in parsing. One simple case in which it was useful 
 was count() that counts how many times a forward range occurs in 
 another. You can't do that with find(). (Try it!)

 I made the executive decision to pass by reference and return a bool.

vote++
 http://d-programming-language.org/cutting-edge/phobos/std_alg
rithm.html#findSkip 



 Andrei

-- 
Graham St Jack