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digitalmars.D.learn - opApply safety

reply Chris Wright <dhasenan gmail.com> writes:
I want to create an opApply for a type.

I've marked my code  safe, because everything I wrote was  safe. The body 
of opApply is  safe, but it calls a delegate that may or may not be  safe.

How do I make it so I can iterate through this type safely and systemly?

I want to support iteration like:

foreach (string key, string value; collection) {}
foreach (size_t i, string key, string value; collection) {}
Jan 29 2016
next sibling parent reply Steven Schveighoffer <schveiguy yahoo.com> writes:
On 1/29/16 12:44 PM, Chris Wright wrote:

 I want to create an opApply for a type.

 I've marked my code  safe, because everything I wrote was  safe. The body
 of opApply is  safe, but it calls a delegate that may or may not be  safe.

 How do I make it so I can iterate through this type safely and systemly?


Likely an overload. Tag the delegate as being  safe or not.

-Steve
Jan 29 2016
parent reply Chris Wright <dhasenan gmail.com> writes:
On Fri, 29 Jan 2016 14:00:08 -0500, Steven Schveighoffer wrote:


 On 1/29/16 12:44 PM, Chris Wright wrote:

 I want to create an opApply for a type.

 I've marked my code  safe, because everything I wrote was  safe. The
 body of opApply is  safe, but it calls a delegate that may or may not
 be  safe.

 How do I make it so I can iterate through this type safely and
 systemly?


 
 Likely an overload. Tag the delegate as being  safe or not.
 
 -Steve


That's handy. It works. I can make it so someone can call:
foo.opApply((i, k, v)  safe => 0);
foo.opApply((i, k, v)  system => 0);

And that works.

However, if you have:
 safe void bar() {
  foreach(i, k, v; foo) {
  }
}

the compiler complains:

opapplysafe.d(12): Error: foo.opApply matches more than one declaration:
opapplysafe.d(2):      safe int(int delegate(int, string, string)  safe 
dg)
and:
opapplysafe.d(5):      system int(int delegate(int, string, string) 
 system dg)

Guess I'll file a bug.
Jan 29 2016
parent Steven Schveighoffer <schveiguy yahoo.com> writes:
On 1/29/16 3:08 PM, Chris Wright wrote:

 On Fri, 29 Jan 2016 14:00:08 -0500, Steven Schveighoffer wrote:


 On 1/29/16 12:44 PM, Chris Wright wrote:

 I want to create an opApply for a type.

 I've marked my code  safe, because everything I wrote was  safe. The
 body of opApply is  safe, but it calls a delegate that may or may not
 be  safe.

 How do I make it so I can iterate through this type safely and
 systemly?


 Likely an overload. Tag the delegate as being  safe or not.

 -Steve


 That's handy. It works. I can make it so someone can call:
 foo.opApply((i, k, v)  safe => 0);
 foo.opApply((i, k, v)  system => 0);

 And that works.

 However, if you have:
  safe void bar() {
    foreach(i, k, v; foo) {
    }
 }

 the compiler complains:

 opapplysafe.d(12): Error: foo.opApply matches more than one declaration:
 opapplysafe.d(2):      safe int(int delegate(int, string, string)  safe
 dg)
 and:
 opapplysafe.d(5):      system int(int delegate(int, string, string)
  system dg)

 Guess I'll file a bug.


Definitely seems like a bug.

As a workaround, you can name the opApply functions:

struct S
{
    int opApply(int delegate(int, string, string)  safe dg)  safe {...}
    int unsafeApply(int delegate(int, string, string) dg) {...}
}

foreach(i, k, v; foo.unsafeApply) {...}

though that's... ugly.

-Steve
Jan 29 2016
prev sibling parent reply Basile B. <b2.temp gmx.com> writes:
On Friday, 29 January 2016 at 17:44:34 UTC, Chris Wright wrote:

 I want to create an opApply for a type.

 I've marked my code  safe, because everything I wrote was 
  safe. The body of opApply is  safe, but it calls a delegate 
 that may or may not be  safe.

 How do I make it so I can iterate through this type safely and 
 systemly?

 I want to support iteration like:

 foreach (string key, string value; collection) {}
 foreach (size_t i, string key, string value; collection) {}


You can implement an input range and annotate all the primitives 
as  safe.
Then if there's only an input range in your agregate, DMD will 
auto-detect that it must use it in foreach():

http://dlang.org/spec/statement.html#foreach-with-ranges

in the worst case (range not implementable directly but only as a 
getter in .range() or .opSlice() you'll have to change the style 
a bit and consume the range explicitly in a typical "while 
(!stuff.empty) {...}"
Jan 29 2016
parent Chris Wright <dhasenan gmail.com> writes:
On Fri, 29 Jan 2016 23:35:35 +0000, Basile B. wrote:

 You can implement an input range and annotate all the primitives as
  safe.


I hadn't realized that if front() returns a tuple, it's automatically 
expanded. Works for me.
Jan 29 2016