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Declaring a reusable formula and using it in other scopes.
Feb 12, 2022
BoQsc
Feb 12, 2022
Basile B.
Feb 12, 2022
H. S. Teoh
February 12, 2022
Gravatar of BoQscPosted by BoQscReply
BoQsc
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bool nextArgumentDoesNotReachEndOfArray = i + 1 < args.length;

How can I declare it out of scope and reuse it in any scope that has i and args.length declared?

February 12, 2022
Gravatar of Basile B.Posted by Basile B.
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Basile B.
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On Saturday, 12 February 2022 at 12:36:06 UTC, BoQsc wrote:

>

bool nextArgumentDoesNotReachEndOfArray = i + 1 < args.length;

How can I declare it out of scope and reuse it in any scope that has i and args.length declared?

Here is an ugly solution, just to encourage someone else to post better:

enum n = "i+1<args.length";

void main()
{
    int i;
    string[] args;
    assert(!mixin(n));
    args.length += 2;
    assert(mixin(n));
    testOtherScope();
}

void testOtherScope()
{
    int i;
    string[] args;
    assert(!mixin(n));
    args.length += 2;
    assert(mixin(n));
}

The problem with that solution is that it's not clean.
The problem of the initial problem is to have automatic capture of i and args in any scope...

Lost cause ?

February 12, 2022
Gravatar of H. S. TeohPosted by H. S. Teoh
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H. S. Teoh
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On Sat, Feb 12, 2022 at 05:52:01PM +0000, Basile B. via Digitalmars-d-learn wrote: [...]
> The problem with that solution is that it's not clean.
> The problem of the initial problem is to have automatic capture of `i`
> and `args` in any scope...
> 
> Lost cause ?

Lost cause, IMO.

Automatic capture of arbitrary identifiers, while it seems useful at first glance, leads to all sorts of problems down the road. Consider, for example, what happens if a typo made it capture something in an outer or global scope, for example. Or if `i` and `args` happen to be defined with the wrong types. Or if somebody modified the mixin to capture something *other* than what you expected it to capture (i.e., encapsulation breakage).  If you work through these unwanted cases, you eventually have to conclude that explicitly passing them as arguments is globally superior, in spite of being locally more inconvenient.


T

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