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POIn Perl, is there any harm in creating a subroutine with the same name as a package?
 

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  1. POIn Perl, is there any harm in creating a subroutine with the same name as a package?
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    <p>Say I have a package called <code>My::Pkg</code>, and that package has a <code>-&gt;new(...)</code> class method to instantiate new objects:</p> <pre><code>package My::Pkg; sub new {bless {@_[1..$#_]} =&gt; $_[0]} </code></pre> <p>Is there any harm in defining the following subroutine:</p> <pre><code>sub My::Pkg {@_ ? My::Pkg::new('My::Pkg', @_) : 'My::Pkg'} </code></pre> <p>So that someone could write:</p> <pre><code>my $obj = My::Pkg one =&gt; 1, two =&gt; 2; </code></pre> <p>Rather than:</p> <pre><code>my $obj = My::Pkg-&gt;new(one =&gt; 1, two =&gt; 2); # which still works, but is longer </code></pre> <p>I like the terseness of the package-named-constructor-subroutine method, but I am interested to know if there are any hidden gotchas to this technique that I have not thought of.</p> <hr> <p>Update:</p> <p>Inheritance works correctly, as shown by the example here:</p> <pre><code>{package a; sub new {say "a::new [@_] ", $_[0]-&gt;init}} {package b; our @ISA = 'a'; sub init {"(b::init [@_])"}} {package a::b; our @ISA = 'b';} sub a::b {print "absub [@_], "; 'a::b'} # a::b() called with no args, returns 'a::b', which then becomes 'a::b'-&gt;new(...) a::b-&gt;new; # absub [], a::new [a::b] (b::init [a::b]) a::b-&gt;new(1, 2, 3); # absub [], a::new [a::b 1 2 3] (b::init [a::b]) # no call to `a::b()` but otherwise the same: 'a::b'-&gt;new; # a::new [a::b] (b::init [a::b]) 'a::b'-&gt;new(1, 2, 3); # a::new [a::b 1 2 3] (b::init [a::b]) new a::b::; # a::new [a::b] (b::init [a::b]) new a::b:: 1, 2, 3; # a::new [a::b 1 2 3] (b::init [a::b]) </code></pre> <p>Interestingly the only thing so far that is different is that the following 2 lines become syntax errors:</p> <pre><code>new a::b; new a::b 1, 2, 3; </code></pre> <p>Which is a syntax error for the same reason <code>some_undefined_sub some_defined_sub;</code> is one.</p> <p>If the <code>new</code> subroutine is defined, it is parsed as <code>new( a::b(...) )</code> which is normal for two adjacent bareword subroutines.</p> <p>Personally, I am ok with <code>new a::b</code> becoming a syntax error, the unambiguous version <code>new a::b::</code> will always work as <em>tchrist</em> helpfully points out below.</p>
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    1. USEric Strom
    1. USEric Strom
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      1. POIn Perl, is there any harm in creating a subroutine with the same name as a package?
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    2. VO
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    1. COSeems clean. If something were to fail, it would be `some_sub My::Pkg a=>1,b=>2;`. It doesn't.
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      1. POIn Perl, is there any harm in creating a subroutine with the same name as a package?
      1. USikegami
    2. CO@ikegami:It most certainly **DOES** fail: `sub X::Y { die "X::Y() called\n" } sub X::Y::new { warn "X::Y::new() called\n" } sub new { die "main::new() called" } $a = new X::Y "business"; warn "got $a";` will die because it calls `main::new(X::Y("business"))` as a subroutine instead of properly invoking `X::Y::new("X::Y", "business"))` as a method. Also, the subroutine call doesn’t respect inheritance as is considered mandatory in an OO world.
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      1. POIn Perl, is there any harm in creating a subroutine with the same name as a package?
      1. UStchrist
    3. COIt is evil that `new X::Y "business"` suddenly means something different from `X::Y->new("business")` — *which* BTW actually now means `X::Y()->new("business")` instead of the `X::Y::new("X::Y", "business")` that everyone thinks it means.
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      1. UStchrist
 

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