Eugen Konkov

Hey.

And I’ve been thinking about the idea of ​​a “soft call” for a long time. Even when writing in ASM always irritated exceptions when CALL 0

Well, here again returned to this topic.

What’s wrong? Very often I have to write the following code:

my $ x; my $ y;
If( ($x = $ obj-> method) && ($y = $x->another_method) ) {
    $ y = ...;
}

An example from life:

If ($ db-> query (...) -> hash -> {value}) {...}
If ($ db-> resultset ('table') -> search (...) -> related_resultset ('table2') {...}

Here if the query returned an empty result, the code will fall.

But when you use a soft call operator, you can not be afraid of exceptions and the code will become easier:

use pragma 'soft_call';

If( my $ x = $ obj-> method ~> another_method ) {...}

If ($db-> query (...) ~> hash -> {value}) {...}

If( $db-> resultset ('table') -> search (...) ~> related_resultset ('table2') {...}

And it seems like everything is expressive.

Even the very implementation of the pragma in a dozen lines:

1. make a plug-in for keyword, like Syntax :: Keyword :: Try
2. cling to http://perldoc.perl.org/perlguts.html#Pluggable-runops
3. Pseudocode

.

sub soft_call_operator {

    my ($ left_operand, $ right_operand) = @_;

    return undef if! defined $left_operand;

    # Do normal processing of the function call
    '->'($left_operand, $right_operand); 
}

I try to google existing analogues and found the Postgres when RETURNS NULL ON NULL INPUT

Comments Wellcome

UPD Thank to choroba for the link. This theme was discussed here