Re: Return data from different types of conditional operation

[wobbles via Digitalmars-d-learn]

On Thursday, 23 April 2015 at 09:48:21 UTC, Dennis Ritchie wrote:

Hi,
Why the program can not return different types of data from the 
conditional operator?


-
import std.stdio;

auto foo() {

if (true) {
return 0;
} else
return "true";
}

void main() {

writeln(foo);
}


Because 0 is an int and "true" is a string.
They're totally different types, and in a statically typed 
language like D, that just wont work.

Re: Return data from different types of conditional operation

[John Colvin via Digitalmars-d-learn]

On Thursday, 23 April 2015 at 09:48:21 UTC, Dennis Ritchie wrote:

Hi,
Why the program can not return different types of data from the 
conditional operator?


-
import std.stdio;

auto foo() {

if (true) {
return 0;
} else
return "true";
}

void main() {

writeln(foo);
}


import std.variant, std.stdio;

auto foo()
{
if (true)
return Variant(0);
else
return Variant("Hello");
}

void main()
{
foo.writeln;
}

Re: Return data from different types of conditional operation

[rumbu via Digitalmars-d-learn]

On Thursday, 23 April 2015 at 10:06:45 UTC, John Colvin wrote:
On Thursday, 23 April 2015 at 09:48:21 UTC, Dennis Ritchie 
wrote:

Hi,
Why the program can not return different types of data from 
the conditional operator?


-
import std.stdio;

auto foo() {

if (true) {
return 0;
} else
return "true";
}

void main() {

writeln(foo);
}


import std.variant, std.stdio;

auto foo()
{
if (true)
return Variant(0);
else
return Variant("Hello");
}

void main()
{
foo.writeln;
}


If 'true' is known at compile time, it works:

auto foo() {

static if (true) {
return 0;
} else
return "true";
}

Re: Return data from different types of conditional operation

[Dennis Ritchie via Digitalmars-d-learn]

Thank you all.
I did not know before, that this behavior is characteristic of 
dynamically typed programming languages.

Re: Return data from different types of conditional operation

[biozic via Digitalmars-d-learn]

On Thursday, 23 April 2015 at 10:26:09 UTC, rumbu wrote:

On Thursday, 23 April 2015 at 10:06:45 UTC, John Colvin wrote:
On Thursday, 23 April 2015 at 09:48:21 UTC, Dennis Ritchie 
wrote:

Hi,
Why the program can not return different types of data from 
the conditional operator?


-
import std.stdio;

auto foo() {

if (true) {
return 0;
} else
return "true";
}

void main() {

writeln(foo);
}


import std.variant, std.stdio;

auto foo()
{
if (true)
return Variant(0);
else
return Variant("Hello");
}

void main()
{
foo.writeln;
}


If 'true' is known at compile time, it works:

auto foo() {

static if (true) {
return 0;
} else
return "true";
}


Yes, but

auto foo() {
static if (true) {
return 0;
} else
this(statment) is [not.parsed];
}

so it's not just working around a problem of returned type 
inference.