[Issue 5515] std.conv.to for safer enum casts

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https://issues.dlang.org/show_bug.cgi?id=5515

Dmitry Olshansky  changed:

   What|Removed |Added

 Status|REOPENED|RESOLVED
 CC||dmitry.o...@gmail.com
 Resolution|--- |FIXED

--- Comment #6 from Dmitry Olshansky  ---
import std.conv: to;
import std.algorithm: map;
enum Foo : char { A='a', B='b', C='c' }
void main() {
auto foos = "abcabcabc".map!(to!Foo)();
}


Compiles today, that was the last of it.

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[Issue 5515] std.conv.to for safer enum casts

[via Digitalmars-d-bugs]

https://issues.dlang.org/show_bug.cgi?id=5515

Andrei Alexandrescu  changed:

   What|Removed |Added

   Keywords||bootcamp
 CC||and...@erdani.com

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[Issue 5515] std.conv.to for safer enum casts

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http://d.puremagic.com/issues/show_bug.cgi?id=5515


Andrej Mitrovic andrej.mitrov...@gmail.com changed:

   What|Removed |Added

 Status|NEW |RESOLVED
 CC||andrej.mitrov...@gmail.com
 Resolution||DUPLICATE


--- Comment #2 from Andrej Mitrovic andrej.mitrov...@gmail.com 2013-02-17 
15:05:24 PST ---
Implemented in Issue8143.

*** This issue has been marked as a duplicate of issue 8143 ***

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[Issue 5515] std.conv.to for safer enum casts

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--- Comment #3 from bearophile_h...@eml.cc 2013-02-17 16:04:00 PST ---
(In reply to comment #2)
 Implemented in Issue8143.
 
 *** This issue has been marked as a duplicate of issue 8143 ***

Given that Enums with floating-point or string base types are not supported.
this is more a WONTFIX :-)

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[Issue 5515] std.conv.to for safer enum casts

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--- Comment #4 from bearophile_h...@eml.cc 2013-02-17 16:33:03 PST ---
But probably this should be supported:


import std.conv: to;
enum Foo : char { A = 'a' }
void main() {
dchar d = 'a';
Foo f = to!Foo(d);
}


Currently it gives:

...\dmd2\src\phobos\std\conv.d(274): Error: template std.conv.toImpl does not
match any function template declaration. Candidates are:
...


It's useful when you want to write (the argument of this map is a dchar):

import std.conv: to;
import std.algorithm: map;
enum Foo : char { A='a', B='b', C='c' }
void main() {
auto foos = abcabcabc.map!(to!Foo)();
}

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Andrej Mitrovic andrej.mitrov...@gmail.com changed:

   What|Removed |Added

 Status|RESOLVED|REOPENED
 Resolution|DUPLICATE   |


--- Comment #5 from Andrej Mitrovic andrej.mitrov...@gmail.com 2013-02-17 
16:46:53 PST ---
(In reply to comment #4)
 But probably this should be supported:
 
 
 import std.conv: to;
 enum Foo : char { A = 'a' }
 void main() {
 dchar d = 'a';
 Foo f = to!Foo(d);
 }

Ok. Reopening issue.

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--- Comment #1 from bearophile_h...@eml.cc 2011-08-18 14:51:07 PDT ---
This enhancement request comes from a handy feature of the Ada language. 

It's not too much hard to implement something similar in D too, with I think an
acceptable final user syntax:


import std.traits: EnumMembers, OriginalType, Unqual;
import std.stdio: writeln;

private E[] convertEnum(E, T)(in T[] data) @safe pure nothrow
if (is(E == enum)  is(Unqual!T == OriginalType!Foo)) {
//assert(__ctfe, This is a compile-time function only.);

E[T] dict;
foreach (member; EnumMembers!E)
dict[member] = member;

auto result = new E[data.length];
foreach (i, item; data)
result[i] = dict[item];
return result;
}

enum Foo : char { A='a', B='b', C='c' }

void show(T)(T x) { writeln(x); }

template F(string s) {
enum F = convertEnum!Foo(s);
}

void main() {
enum Foo[][] foos = [F!abcabcabc,
 F!cbacbacba];
//import std.conv;
//const Foo[] foos2 = to!(Foo[])(abcabcabc); // not possible yet
show(foos); // [[A, B, C, A, B, C, A, B, C],
//  [C, B, A, C, B, A, C, B, A]]
}


Still, I think safe compile-time Enum conversion and safe run-time Enum
conversion is a feature worth folding inside to!().

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