Re: std.string.indexOf with an optional start-at parameter?
On Mon, 04 Apr 2011 10:10:00 -0400, Andrei Alexandrescu wrote: On 4/4/11 8:18 AM, Steven Schveighoffer wrote: On Sun, 03 Apr 2011 14:24:33 -0400, spir wrote: On 04/03/2011 07:39 PM, Aleksandar Ružičić wrote: I needed std.string.indexOf to accept start position in the string to start the search at. I was really surprised when I realized that this (to me) standard parameter is "missing" (I'm used to indexOf in javascript, strpos in php and equivalent methods in other languages, which support start offset parameter). There might be some other function (in some other module) that does what I want but I wasn't able to find it (I find D's documentation not easy to search and read), so I've copied indexOf to my module and added wanted functionality: https://gist.github.com/900589 now, I'm able to write, for example: auto pos = indexOf(haystack, '$', 10); // will starts search at 11th char in haystack and auto pos = indexOf(haystack, '$', -5); // will starts search at 5th char from the end My question is: is there a reason why there is no this functionality in phobos (maybe there's some language feature I'm not aware of?) and if no such reason exists, would it be possible to add it in future version of phobos/dmd? Agreed this is a fairly standard param in other languages, but D easily (and rather cheaply) allows auto pos = indexOf(s[i..$], char); That doesn't work, because it gets you the position in relation to s[i..$], whereas you want the position in relation to s. I think the requested feature is common enough to warrant inclusion, especially since it could take care of out-of-bounds problems where slicing would throw an error instead. To write the equivalent would be very non-trivial. -Steve I'm worried that most people will want and mean n in indexOf(haystack, needle, n) as "start from the nth character from the front (or back)". Then we need the slower algorithm. Using a slice clarifies the intent on the caller's side. I was about to write "what does that mean?", but I see what you mean now. I look at the most important part of this as, when you search on a slice, the result is a number that has to be re-adjusted based on the slice. That is, if I could get the right value by doing indexOf(s[5..$], "abc"), then it would be great to just accept slices, but that returns the result offset by the slice. So you have to re-adjust the return value: indexOf(s[5..$], "abc") + 5. This is a little annoying, and dangerous, especially if the offset (5 in this example) is not a simple literal. There are very very easy ways to write this incorrectly. What if we had a different function name to re-assert intent? indexOfSlice(haystack, needle, slicestart, sliceend) where sliceend was optional? -Steve
Re: std.string.indexOf with an optional start-at parameter?
On 4/4/11 8:18 AM, Steven Schveighoffer wrote: On Sun, 03 Apr 2011 14:24:33 -0400, spir wrote: On 04/03/2011 07:39 PM, Aleksandar Ružičić wrote: I needed std.string.indexOf to accept start position in the string to start the search at. I was really surprised when I realized that this (to me) standard parameter is "missing" (I'm used to indexOf in javascript, strpos in php and equivalent methods in other languages, which support start offset parameter). There might be some other function (in some other module) that does what I want but I wasn't able to find it (I find D's documentation not easy to search and read), so I've copied indexOf to my module and added wanted functionality: https://gist.github.com/900589 now, I'm able to write, for example: auto pos = indexOf(haystack, '$', 10); // will starts search at 11th char in haystack and auto pos = indexOf(haystack, '$', -5); // will starts search at 5th char from the end My question is: is there a reason why there is no this functionality in phobos (maybe there's some language feature I'm not aware of?) and if no such reason exists, would it be possible to add it in future version of phobos/dmd? Agreed this is a fairly standard param in other languages, but D easily (and rather cheaply) allows auto pos = indexOf(s[i..$], char); That doesn't work, because it gets you the position in relation to s[i..$], whereas you want the position in relation to s. I think the requested feature is common enough to warrant inclusion, especially since it could take care of out-of-bounds problems where slicing would throw an error instead. To write the equivalent would be very non-trivial. -Steve I'm worried that most people will want and mean n in indexOf(haystack, needle, n) as "start from the nth character from the front (or back)". Then we need the slower algorithm. Using a slice clarifies the intent on the caller's side. Andrei
Re: std.string.indexOf with an optional start-at parameter?
On Mon, Apr 4, 2011 at 3:18 PM, Steven Schveighoffer
wrote:
> On Sun, 03 Apr 2011 14:24:33 -0400, spir wrote:
>> Agreed this is a fairly standard param in other languages, but D easily
>> (and rather cheaply) allows
>> auto pos = indexOf(s[i..$], char);
>
> That doesn't work, because it gets you the position in relation to s[i..$],
> whereas you want the position in relation to s.
>
This works:
---
sizediff_t
indexOf(Char, T = sizediff_t)(in Char[] s, dchar c, T sp = 0)
if (isSomeChar!Char)
{
if (sp < 0)
sp += s.length;
if (sp >= 0 && sp < s.length)
{
auto i = indexOf(s[sp..$], c);
if (i > -1)
return i + sp;
}
return -1;
}
---
And it doesn't require change of existing indexOf.
Re: std.string.indexOf with an optional start-at parameter?
On Sun, 03 Apr 2011 14:24:33 -0400, spir wrote: On 04/03/2011 07:39 PM, Aleksandar Ružičić wrote: I needed std.string.indexOf to accept start position in the string to start the search at. I was really surprised when I realized that this (to me) standard parameter is "missing" (I'm used to indexOf in javascript, strpos in php and equivalent methods in other languages, which support start offset parameter). There might be some other function (in some other module) that does what I want but I wasn't able to find it (I find D's documentation not easy to search and read), so I've copied indexOf to my module and added wanted functionality: https://gist.github.com/900589 now, I'm able to write, for example: auto pos = indexOf(haystack, '$', 10); // will starts search at 11th char in haystack and auto pos = indexOf(haystack, '$', -5); // will starts search at 5th char from the end My question is: is there a reason why there is no this functionality in phobos (maybe there's some language feature I'm not aware of?) and if no such reason exists, would it be possible to add it in future version of phobos/dmd? Agreed this is a fairly standard param in other languages, but D easily (and rather cheaply) allows auto pos = indexOf(s[i..$], char); That doesn't work, because it gets you the position in relation to s[i..$], whereas you want the position in relation to s. I think the requested feature is common enough to warrant inclusion, especially since it could take care of out-of-bounds problems where slicing would throw an error instead. To write the equivalent would be very non-trivial. -Steve
Re: std.string.indexOf with an optional start-at parameter?
On Sun, Apr 3, 2011 at 10:56 PM, KennyTM~ wrote:
>> And javascript _does_ have true arrays, but it _doesn't_ have true
>> associative arrays (those are object literals).
>>
>
> I would not call it a true array if it is indexed by string internally.
> Anyway, this is not the main point.
>
You're right that JS arrays are not a point here, but I must again
disagree with you :)
I write Javascript code for living, so I think I know what I'm talking about:
var a = ["foo", "bar", "baz"]; // defining an array
a[0];// "foo"
a["0"]; // this would also work, but only because JS casts "0" to
integer implicitly
there is no string indexing with arrays, only with objects
(associative arrays, maps, call it as you like):
var o = {foo: "bar", 0: "baz"}; // defining an object (a.k.a AA)
o.foo; // "bar"
o["foo"]; // same, returns "bar"
o[0]; // "baz" now, this just looks like indexing an array,
but it really ain't, it's property getter, but JS allows you have
numeric properties so it can be confusing, I admit.
That's all I have to say about JS arrays, won't be talking non-D anymore :)
Regards,
Aleksandar
Re: std.string.indexOf with an optional start-at parameter?
On Apr 4, 11 04:07, Aleksandar Ružičić wrote: You mean Python and Ruby. - Javascript does not support negative index. In fact, JS has no true arrays, it only has associative array. - PHP does not support negative index. http://ideone.com/8MZ2T I was talking about javascript's String.prototype.indexOf () and php's strpos functions, not about array indexing. I see. But even for that I wasn't correct :/. Negative start-at index is avaliable for substr (both, in php and js), that's why I have confused it with indexOf (I thought these things are consistent..) PHP will never be consistent. ;) And javascript _does_ have true arrays, but it _doesn't_ have true associative arrays (those are object literals). I would not call it a true array if it is indexed by string internally. Anyway, this is not the main point. This does not mean negative index is useless (I use it all the time when programming in Python), but D shouldn't add a feature just because other languages have it, or even you think that language had it. I know, I was just expressing my opinion (what I would like to see in a language, I never programmed in phyton or perl, so I was thinking that negative indices for array indexing are not supported in any language that I know of), I wasn't proposing a new feature :) Right.
Re: std.string.indexOf with an optional start-at parameter?
> You mean Python and Ruby. > > - Javascript does not support negative index. In fact, JS has no true > arrays, it only has associative array. > - PHP does not support negative index. http://ideone.com/8MZ2T I was talking about javascript's String.prototype.indexOf () and php's strpos functions, not about array indexing. But even for that I wasn't correct :/. Negative start-at index is avaliable for substr (both, in php and js), that's why I have confused it with indexOf (I thought these things are consistent..) And javascript _does_ have true arrays, but it _doesn't_ have true associative arrays (those are object literals). > This does not mean negative index is useless (I use it all the time when > programming in Python), but D shouldn't add a feature just because other > languages have it, or even you think that language had it. I know, I was just expressing my opinion (what I would like to see in a language, I never programmed in phyton or perl, so I was thinking that negative indices for array indexing are not supported in any language that I know of), I wasn't proposing a new feature :)
Re: std.string.indexOf with an optional start-at parameter?
On Apr 4, 11 02:29, Aleksandar Ružičić wrote: On Sun, Apr 3, 2011 at 8:16 PM, Andrei Alexandrescu wrote: It's not. Seems I've missed that in the docs, I tought it will always make a copy :) I think that's a natural and simple improvement of indexOf. The one aspect that I'm unsure about is starting from the end for negative indices. Negative indices might seem a bit odd but it's standard in other languages (like javascript and php which I've already mentioned). I would even like to see this in D: You mean Python and Ruby. - Javascript does not support negative index. In fact, JS has no true arrays, it only has associative array. - PHP does not support negative index. http://ideone.com/8MZ2T Many other languages that I've heard of like C#, C, C++, Go, Haskell and Java also do not support negative index. Also, interestingly, Perl 5 had negative index, but Perl 6 killed it. (http://perlcabal.org/syn/S09.html#Negative_and_differential_subscripts) "The Perl 6 semantics avoids indexing discontinuities (a source of subtle runtime errors), and provides ordinal access in both directions at both ends of the array." This does not mean negative index is useless (I use it all the time when programming in Python), but D shouldn't add a feature just because other languages have it, or even you think that language had it. array[-2]; // get 'a' from "foobar" same for slicing: array[-4..2]; // get "ob" from "foobar" Could you please submit an enhancement request to bugzilla? sure!
Re: std.string.indexOf with an optional start-at parameter?
On Apr 4, 11 02:24, spir wrote: On 04/03/2011 07:39 PM, Aleksandar Ružičić wrote: I needed std.string.indexOf to accept start position in the string to start the search at. I was really surprised when I realized that this (to me) standard parameter is "missing" (I'm used to indexOf in javascript, strpos in php and equivalent methods in other languages, which support start offset parameter). There might be some other function (in some other module) that does what I want but I wasn't able to find it (I find D's documentation not easy to search and read), so I've copied indexOf to my module and added wanted functionality: https://gist.github.com/900589 now, I'm able to write, for example: auto pos = indexOf(haystack, '$', 10); // will starts search at 11th char in haystack and auto pos = indexOf(haystack, '$', -5); // will starts search at 5th char from the end My question is: is there a reason why there is no this functionality in phobos (maybe there's some language feature I'm not aware of?) and if no such reason exists, would it be possible to add it in future version of phobos/dmd? Agreed this is a fairly standard param in other languages, but D easily (and rather cheaply) allows auto pos = indexOf(s[i..$], char); I would be far more interested in generalised negative inices in D --à la Python. A great step for D's friendliness, and an final end to current '$' issues (1). Denis (1) Which works only for builtin type via compiler magic, because it neither maps to .length, nore is overloadable. There should be opDollar http://d.puremagic.com/issues/show_bug.cgi?id=3474.
Re: std.string.indexOf with an optional start-at parameter?
On Sun, Apr 3, 2011 at 8:16 PM, Andrei Alexandrescu wrote: > It's not. Seems I've missed that in the docs, I tought it will always make a copy :) > I think that's a natural and simple improvement of indexOf. The one aspect > that I'm unsure about is starting from the end for negative indices. Negative indices might seem a bit odd but it's standard in other languages (like javascript and php which I've already mentioned). I would even like to see this in D: array[-2]; // get 'a' from "foobar" same for slicing: array[-4..2]; // get "ob" from "foobar" > Could you please submit an enhancement request to bugzilla? sure!
Re: std.string.indexOf with an optional start-at parameter?
On 04/03/2011 07:39 PM, Aleksandar Ružičić wrote: I needed std.string.indexOf to accept start position in the string to start the search at. I was really surprised when I realized that this (to me) standard parameter is "missing" (I'm used to indexOf in javascript, strpos in php and equivalent methods in other languages, which support start offset parameter). There might be some other function (in some other module) that does what I want but I wasn't able to find it (I find D's documentation not easy to search and read), so I've copied indexOf to my module and added wanted functionality: https://gist.github.com/900589 now, I'm able to write, for example: auto pos = indexOf(haystack, '$', 10); // will starts search at 11th char in haystack and auto pos = indexOf(haystack, '$', -5); // will starts search at 5th char from the end My question is: is there a reason why there is no this functionality in phobos (maybe there's some language feature I'm not aware of?) and if no such reason exists, would it be possible to add it in future version of phobos/dmd? Agreed this is a fairly standard param in other languages, but D easily (and rather cheaply) allows auto pos = indexOf(s[i..$], char); I would be far more interested in generalised negative inices in D --à la Python. A great step for D's friendliness, and an final end to current '$' issues (1). Denis (1) Which works only for builtin type via compiler magic, because it neither maps to .length, nore is overloadable. -- _ vita es estrany spir.wikidot.com
Re: std.string.indexOf with an optional start-at parameter?
On 4/3/11 1:14 PM, Aleksandar Ružičić wrote: I thought first of slicing, but isn't that making a copy of string? It's not. And also, if I'm not mistaken if you slice out of range bounds (i.e. haystack[5..$] when haystack.length< 5) you'll get exception, right? Correct. That's why I think this would be nice to have feature, so you don't have to worry if start position is within the string bounds, and you won't need to write this: I think that's a natural and simple improvement of indexOf. The one aspect that I'm unsure about is starting from the end for negative indices. Could you please submit an enhancement request to bugzilla? Andrei
Re: std.string.indexOf with an optional start-at parameter?
I thought first of slicing, but isn't that making a copy of string? And also, if I'm not mistaken if you slice out of range bounds (i.e. haystack[5..$] when haystack.length < 5) you'll get exception, right? That's why I think this would be nice to have feature, so you don't have to worry if start position is within the string bounds, and you won't need to write this: > auto pos = indexOf(haystack[$-5..$], '$') + haystack.length-5; when you want to start search from the end (since it's somehow less readable than indexOf(haystack, '$', -5)). On Sun, Apr 3, 2011 at 7:55 PM, Robert Jacques wrote: > On Sun, 03 Apr 2011 13:39:40 -0400, Aleksandar Ružičić > wrote: > >> I needed std.string.indexOf to accept start position in the string to >> start the search at. I was really surprised when I realized that this >> (to me) standard parameter is "missing" (I'm used to indexOf in >> javascript, strpos in php and equivalent methods in other languages, >> which support start offset parameter). >> >> There might be some other function (in some other module) that does >> what I want but I wasn't able to find it (I find D's documentation not >> easy to search and read), so I've copied indexOf to my module and >> added wanted functionality: >> >> https://gist.github.com/900589 >> >> now, I'm able to write, for example: >> >> auto pos = indexOf(haystack, '$', 10); // will starts search at 11th >> char in haystack > > auto pos = indexOf(haystack[10..$], '$') + 10; > >> and >> >> auto pos = indexOf(haystack, '$', -5); // will starts search at 5th >> char from the end > > auto pos = indexOf(haystack[$-5..$], '$') + haystack.length-5; > >> My question is: is there a reason why there is no this functionality >> in phobos (maybe there's some language feature I'm not aware of?) and >> if no such reason exists, would it be possible to add it in future >> version of phobos/dmd? > > Yes, the language feature is called slicing. See above. Also, you may want > to look at the various find methods in std.algorithm. Generally, it's better > to work with ranges/slices than indexes due to UTF's encoding scheme. >
Re: std.string.indexOf with an optional start-at parameter?
On Sun, 03 Apr 2011 13:39:40 -0400, Aleksandar Ružičić wrote: I needed std.string.indexOf to accept start position in the string to start the search at. I was really surprised when I realized that this (to me) standard parameter is "missing" (I'm used to indexOf in javascript, strpos in php and equivalent methods in other languages, which support start offset parameter). There might be some other function (in some other module) that does what I want but I wasn't able to find it (I find D's documentation not easy to search and read), so I've copied indexOf to my module and added wanted functionality: https://gist.github.com/900589 now, I'm able to write, for example: auto pos = indexOf(haystack, '$', 10); // will starts search at 11th char in haystack auto pos = indexOf(haystack[10..$], '$') + 10; and auto pos = indexOf(haystack, '$', -5); // will starts search at 5th char from the end auto pos = indexOf(haystack[$-5..$], '$') + haystack.length-5; My question is: is there a reason why there is no this functionality in phobos (maybe there's some language feature I'm not aware of?) and if no such reason exists, would it be possible to add it in future version of phobos/dmd? Yes, the language feature is called slicing. See above. Also, you may want to look at the various find methods in std.algorithm. Generally, it's better to work with ranges/slices than indexes due to UTF's encoding scheme.
std.string.indexOf with an optional start-at parameter?
I needed std.string.indexOf to accept start position in the string to start the search at. I was really surprised when I realized that this (to me) standard parameter is "missing" (I'm used to indexOf in javascript, strpos in php and equivalent methods in other languages, which support start offset parameter). There might be some other function (in some other module) that does what I want but I wasn't able to find it (I find D's documentation not easy to search and read), so I've copied indexOf to my module and added wanted functionality: https://gist.github.com/900589 now, I'm able to write, for example: auto pos = indexOf(haystack, '$', 10); // will starts search at 11th char in haystack and auto pos = indexOf(haystack, '$', -5); // will starts search at 5th char from the end My question is: is there a reason why there is no this functionality in phobos (maybe there's some language feature I'm not aware of?) and if no such reason exists, would it be possible to add it in future version of phobos/dmd?
