Re: to auto or not to auto ( in foreach )
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: On Sunday, 17 July 2016 at 01:57:21 UTC, pineapple wrote: 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. Furthermore, if foreach(int x; y) is legal then why isn't foreach(auto x; y)? 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 ? 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 ?
Re: to auto or not to auto ( in foreach )
On Sunday, 17 July 2016 at 01:58:59 UTC, pineapple wrote: On Sunday, 17 July 2016 at 01:57:21 UTC, pineapple wrote: 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. Furthermore, if foreach(int x; y) is legal then why isn't foreach(auto x; y)? 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 ?
Re: to auto or not to auto ( in foreach )
On Saturday, 16 July 2016 at 22:05:49 UTC, ketmar wrote: `foreach (v; rng)` looks like `foreach` is *reusing* *existing* *variable*. +1
Re: to auto or not to auto ( in foreach )
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.
Re: to auto or not to auto ( in foreach )
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.
Re: to auto or not to auto ( in foreach )
On Sunday, 17 July 2016 at 01:57:21 UTC, pineapple wrote: 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. Furthermore, if foreach(int x; y) is legal then why isn't foreach(auto x; y)?
Re: to auto or not to auto ( in foreach )
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.
Re: to auto or not to auto ( in foreach )
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)
Re: to auto or not to auto ( in foreach )
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
Re: to auto or not to auto ( in foreach )
On Saturday, 16 July 2016 at 20:00:39 UTC, Seb wrote: On Saturday, 16 July 2016 at 14:11:34 UTC, cym13 wrote: 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. 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. 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.
Re: to auto or not to auto ( in foreach )
On Saturday, 16 July 2016 at 20:00:39 UTC, Seb wrote: On Saturday, 16 July 2016 at 14:11:34 UTC, cym13 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. However I agree that the error message should be more informative. Please open a issue for this ;-)
Re: to auto or not to auto ( in foreach )
On Saturday, 16 July 2016 at 14:11:34 UTC, cym13 wrote: 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. 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.
Re: to auto or not to auto ( in foreach )
On Saturday, 16 July 2016 at 14:00:56 UTC, dom wrote: .. but why? because. i've lost that fight too.
Re: to auto or not to auto ( in foreach )
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.
Re: to auto or not to auto ( in foreach )
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
