digitalmars.D.learn - to auto or not to auto ( in foreach )
- dom (7/7) Jul 16 2016 foreach(auto v; msg)
- Dennis Ritchie (5/12) Jul 16 2016 `Note: The ForeachTypeAttribute is implicit, and when a type is
- cym13 (6/13) Jul 16 2016 Arbitrary limitation. If you want to say how surprising and
- Seb (9/26) Jul 16 2016 It's not arbitrary. It keeps the language simple and easy to
- Seb (3/13) Jul 16 2016 However I agree that the error message should be more
- cym13 (12/40) Jul 16 2016 int int is a completely different issue, and that has nothing to
- cym13 (2/3) Jul 16 2016 -> A variable definition *with auto* in a foreach
- ketmar (6/13) Jul 16 2016 actually, `foreach (v; rng)` looks like `foreach` is *reusing*
- pineapple (6/11) Jul 16 2016 Chipping in my agreement. foreach(x; y) makes as much syntactic
- pineapple (3/15) Jul 16 2016 Furthermore, if foreach(int x; y) is legal then why isn't
- Lobelia Noakes (8/24) Jul 20 2016 By the way there's an error in the grammar:
- Lobelia Noakes (6/31) Jul 20 2016 It's a minor issue BTW. I think that everybody that would write a
- Adam D. Ruppe (3/8) Jul 16 2016 (x) => x; // defines a new variable
- ketmar (2/4) Jul 16 2016 compiler should allow `auto` here too.
- Johan Engelen (2/5) Jul 18 2016 +1
- ketmar (2/3) Jul 16 2016 because. i've lost that fight too.
foreach(auto v; msg) writeln(v); gives an error that a basic type is expected foreach(v; msg) writeln(v); works .. but why?
Jul 16 2016
On Saturday, 16 July 2016 at 14:00:56 UTC, dom wrote:foreach(auto v; msg) writeln(v); gives an error that a basic type is expected foreach(v; msg) writeln(v); works .. but why?`Note: The ForeachTypeAttribute is implicit, and when a type is not specified, it is inferred. In that case, auto is implied, and it is not necessary (and actually forbidden) to use it.` http://dlang.org/spec/statement.html#ForeachStatement
Jul 16 2016
On Saturday, 16 July 2016 at 14:00:56 UTC, dom wrote:foreach(auto v; msg) writeln(v); gives an error that a basic type is expected foreach(v; msg) writeln(v); works .. but why?Arbitrary limitation. If you want to say how surprising and uselessly limiting it is wait at the end of the line. It's not actually a problem in practice because you just have not to put it but it is part of those frustrating little edge cases with no reason to be.
Jul 16 2016
On Saturday, 16 July 2016 at 14:11:34 UTC, cym13 wrote:On Saturday, 16 July 2016 at 14:00:56 UTC, dom wrote:It's not arbitrary. It keeps the language simple and easy to read. After all the entire auto keyword is just there, because the compiler needs a keyword and in loops it's clearly defined what the type will be. You don't complain that `int int` is forbidden, or do you? I guess you are frustrated because you are used to this pattern from other, inferior languages. I bet you will soon start to appreciate the syntactic sugar that D provides.foreach(auto v; msg) writeln(v); gives an error that a basic type is expected foreach(v; msg) writeln(v); works .. but why?Arbitrary limitation. If you want to say how surprising and uselessly limiting it is wait at the end of the line. It's not actually a problem in practice because you just have not to put it but it is part of those frustrating little edge cases with no reason to be.
Jul 16 2016
On Saturday, 16 July 2016 at 20:00:39 UTC, Seb wrote:On Saturday, 16 July 2016 at 14:11:34 UTC, cym13 wrote:However I agree that the error message should be more informative. Please open a issue for this ;-)[...]It's not arbitrary. It keeps the language simple and easy to read. After all the entire auto keyword is just there, because the compiler needs a keyword and in loops it's clearly defined what the type will be. You don't complain that `int int` is forbidden, or do you? I guess you are frustrated because you are used to this pattern from other, inferior languages. I bet you will soon start to appreciate the syntactic sugar that D provides.
Jul 16 2016
On Saturday, 16 July 2016 at 20:00:39 UTC, Seb wrote:On Saturday, 16 July 2016 at 14:11:34 UTC, cym13 wrote:int int is a completely different issue, and that has nothing to do with what you suppose my experience is from other languages. If anything I come mainly from python so I find not having to write the type a pretty thing. However auto should be allowed here. You are defining a variable and the fact that it's in a foreach shouldn't be of any importance. The language should enforce orthogonality of orthogonal things, not break it. A variable definition in a foreach should be allowed not because I like to be pedantic but because it's allowed everywhere else. That also stands for the principle of least surprise.On Saturday, 16 July 2016 at 14:00:56 UTC, dom wrote:It's not arbitrary. It keeps the language simple and easy to read. After all the entire auto keyword is just there, because the compiler needs a keyword and in loops it's clearly defined what the type will be. You don't complain that `int int` is forbidden, or do you? I guess you are frustrated because you are used to this pattern from other, inferior languages. I bet you will soon start to appreciate the syntactic sugar that D provides.foreach(auto v; msg) writeln(v); gives an error that a basic type is expected foreach(v; msg) writeln(v); works .. but why?Arbitrary limitation. If you want to say how surprising and uselessly limiting it is wait at the end of the line. It's not actually a problem in practice because you just have not to put it but it is part of those frustrating little edge cases with no reason to be.
Jul 16 2016
On Saturday, 16 July 2016 at 21:39:42 UTC, cym13 wrote:A variable definition in a foreach-> A variable definition *with auto* in a foreach
Jul 16 2016
On Saturday, 16 July 2016 at 21:39:42 UTC, cym13 wrote:However auto should be allowed here. You are defining a variable and the fact that it's in a foreach shouldn't be of any importance. The language should enforce orthogonality of orthogonal things, not break it. A variable definition in a foreach should be allowed not because I like to be pedantic but because it's allowed everywhere else. That also stands for the principle of least surprise.actually, `foreach (v; rng)` looks like `foreach` is *reusing* *existing* *variable*. most of the time you can put `immutable` or something like that there to note that it is not reusing (purely cosmetical thing), but sometimes you cannot, and then `auto` is perfect candidate... but it is not allowed. (sigh)
Jul 16 2016
On Saturday, 16 July 2016 at 22:05:49 UTC, ketmar wrote:actually, `foreach (v; rng)` looks like `foreach` is *reusing* *existing* *variable*. most of the time you can put `immutable` or something like that there to note that it is not reusing (purely cosmetical thing), but sometimes you cannot, and then `auto` is perfect candidate... but it is not allowed. (sigh)Chipping in my agreement. foreach(x; y) makes as much syntactic sense as for(x = 0; x < y; x++) where x was not previously defined. One does not expect something that does not look like every other variable definition in the language to be defining a new variable.
Jul 16 2016
On Sunday, 17 July 2016 at 01:57:21 UTC, pineapple wrote:On Saturday, 16 July 2016 at 22:05:49 UTC, ketmar wrote:Furthermore, if foreach(int x; y) is legal then why isn't foreach(auto x; y)?actually, `foreach (v; rng)` looks like `foreach` is *reusing* *existing* *variable*. most of the time you can put `immutable` or something like that there to note that it is not reusing (purely cosmetical thing), but sometimes you cannot, and then `auto` is perfect candidate... but it is not allowed. (sigh)Chipping in my agreement. foreach(x; y) makes as much syntactic sense as for(x = 0; x < y; x++) where x was not previously defined. One does not expect something that does not look like every other variable definition in the language to be defining a new variable.
Jul 16 2016
On Sunday, 17 July 2016 at 01:58:59 UTC, pineapple wrote:On Sunday, 17 July 2016 at 01:57:21 UTC, pineapple wrote:By the way there's an error in the grammar: ForeachTypeAttribute: ref TypeCtor But BasicType also already includes TypeCtor. So a TypeCtor in a foreach typelist is ? well hard to say, part of basic type or part of ForeachTypeAttribute ?On Saturday, 16 July 2016 at 22:05:49 UTC, ketmar wrote:Furthermore, if foreach(int x; y) is legal then why isn't foreach(auto x; y)?actually, `foreach (v; rng)` looks like `foreach` is *reusing* *existing* *variable*. most of the time you can put `immutable` or something like that there to note that it is not reusing (purely cosmetical thing), but sometimes you cannot, and then `auto` is perfect candidate... but it is not allowed. (sigh)Chipping in my agreement. foreach(x; y) makes as much syntactic sense as for(x = 0; x < y; x++) where x was not previously defined. One does not expect something that does not look like every other variable definition in the language to be defining a new variable.
Jul 20 2016
On Wednesday, 20 July 2016 at 15:40:16 UTC, Lobelia Noakes wrote:On Sunday, 17 July 2016 at 01:58:59 UTC, pineapple wrote:It's a minor issue BTW. I think that everybody that would write a D parser will skip parsing of TypeCtor in ForeachTypeAttribute and rather consider them as part of the type. I'm not sure if it can be completly removed from ForeachTypeAttribute...Does anyone know ?On Sunday, 17 July 2016 at 01:57:21 UTC, pineapple wrote:By the way there's an error in the grammar: ForeachTypeAttribute: ref TypeCtor But BasicType also already includes TypeCtor. So a TypeCtor in a foreach typelist is ? well hard to say, part of basic type or part of ForeachTypeAttribute ?On Saturday, 16 July 2016 at 22:05:49 UTC, ketmar wrote:Furthermore, if foreach(int x; y) is legal then why isn't foreach(auto x; y)?actually, `foreach (v; rng)` looks like `foreach` is *reusing* *existing* *variable*. most of the time you can put `immutable` or something like that there to note that it is not reusing (purely cosmetical thing), but sometimes you cannot, and then `auto` is perfect candidate... but it is not allowed. (sigh)Chipping in my agreement. foreach(x; y) makes as much syntactic sense as for(x = 0; x < y; x++) where x was not previously defined. One does not expect something that does not look like every other variable definition in the language to be defining a new variable.
Jul 20 2016
On Sunday, 17 July 2016 at 01:57:21 UTC, pineapple wrote:Chipping in my agreement. foreach(x; y) makes as much syntactic sense as for(x = 0; x < y; x++) where x was not previously defined. One does not expect something that does not look like every other variable definition in the language to be defining a new variable.(x) => x; // defines a new variable foreach isn't alone.
Jul 16 2016
On Sunday, 17 July 2016 at 02:04:50 UTC, Adam D. Ruppe wrote:(x) => x; // defines a new variable foreach isn't alone.compiler should allow `auto` here too.
Jul 16 2016
On Saturday, 16 July 2016 at 22:05:49 UTC, ketmar wrote:`foreach (v; rng)` looks like `foreach` is *reusing* *existing* *variable*.+1
Jul 18 2016
On Saturday, 16 July 2016 at 14:00:56 UTC, dom wrote:.. but why?because. i've lost that fight too.
Jul 16 2016