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digitalmars.D.learn - Function template advice

reply Jordan Wilson <wilsonjord gmail.com> writes:
I have a simple comparison function:

struct Foo {
     string bar;
}

auto sameGroup(T,S) (T a, S b) {
     static assert (is(T == string) || is(T == Foo));
     static assert (is(S == string) || is(S == Foo));

     string aStr;
     string bStr;
     static if (is(T == string)){
         aStr = a;
     } else {
         aStr = a.bar;
     }
     static if (is(S == string)){
         bStr = b;
     } else {
         bStr = b.bar;
     }
     return equal (aStr,bStr);
}

This works, but just wondered if there was an easier way?

Is there a way to do "static if" in shorthand, like:
auto aStr = (static if (is(T==string)) ? a : a.bar
Jan 18 2017
parent reply =?UTF-8?Q?Ali_=c3=87ehreli?= <acehreli yahoo.com> writes:
On 01/18/2017 02:02 PM, Jordan Wilson wrote:

 I have a simple comparison function:

 struct Foo {
     string bar;
 }

 auto sameGroup(T,S) (T a, S b) {
     static assert (is(T == string) || is(T == Foo));
     static assert (is(S == string) || is(S == Foo));

     string aStr;
     string bStr;
     static if (is(T == string)){
         aStr = a;
     } else {
         aStr = a.bar;
     }
     static if (is(S == string)){
         bStr = b;
     } else {
         bStr = b.bar;
     }
     return equal (aStr,bStr);
 }

 This works, but just wondered if there was an easier way?

 Is there a way to do "static if" in shorthand, like:
 auto aStr = (static if (is(T==string)) ? a : a.bar


Yes, can be better with something similar to the following:

struct Foo {
     string bar;
}

string value(U : Foo)(U u) {
     return u.bar;
}

string value(U : string)(U u) {
     return u;
}

auto sameGroup(T,S) (T a, S b) {
     static assert (is(T == string) || is(T == Foo));
     static assert (is(S == string) || is(S == Foo));

     import std.algorithm;
     return equal (value(a), value(b));
}

void main() {
     assert(sameGroup("a", "b") == false);
     assert(sameGroup("a", Foo("a")) == true);
     assert(sameGroup(Foo("x"), "b") == false);
     assert(sameGroup(Foo("z"), Foo("z")) == true);
}

Ali
Jan 18 2017
parent Jordan Wilson <wilsonjord gmail.com> writes:
On Wednesday, 18 January 2017 at 22:39:02 UTC, Ali Çehreli wrote:

 On 01/18/2017 02:02 PM, Jordan Wilson wrote:

 [...]


 Yes, can be better with something similar to the following:

 struct Foo {
     string bar;
 }

 string value(U : Foo)(U u) {
     return u.bar;
 }

 string value(U : string)(U u) {
     return u;
 }

 auto sameGroup(T,S) (T a, S b) {
     static assert (is(T == string) || is(T == Foo));
     static assert (is(S == string) || is(S == Foo));

     import std.algorithm;
     return equal (value(a), value(b));
 }

 void main() {
     assert(sameGroup("a", "b") == false);
     assert(sameGroup("a", Foo("a")) == true);
     assert(sameGroup(Foo("x"), "b") == false);
     assert(sameGroup(Foo("z"), Foo("z")) == true);
 }

 Ali


Nice, yes looks better thanks.
Jordan
Jan 18 2017