short-circuiting method conjunction?
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From: Terrence Brannon
Subject: short-circuiting method conjunction?
Date: 22:40 on 23 Nov 2004
Subject: short-circuiting method conjunction?
Date: 22:40 on 23 Nov 2004
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We all know that simple scalars can be chained together;
=20
$boolean =3D $this and $that or $the_other;
=20
I'm sure many of you have used Perl methods which return objects
which
you can use again in a chain like so:
=20
push @status_options, 'hidden' if=20
GCt::glyph_attribute->retrieve(=20
glyph_type =3D> $glyph_type, =20
attr_name =3D> 'face_hideable'=20
)=20
->attr_value;
=20
It would be neat if there were some method-chaining syntax/module
which
indicated "return false if your method call returns false":
=20
$object-?->method1-?->method2-?->method3
=20
One solution appears to be Pipeline:
=20
http://search.cpan.org/~rclamp/Pipeline-3.12/lib/Pipeline.pm
=20
What I currently do is wrap the method chain in an eval block and
check
to see if a Boolean was set within the block:
=20
{
my $boolean;
=20
eval {
$boolean =3D=20
GCt::glyph_attribute->retrieve
(=20
glyph_type =3D> $glyph_type, =20
attr_name =3D> 'face_hideable'=20
)=20
->attr_value;
}
}
=20
push @status_options, 'hidden' if $boolean;
=20
but that is much wordier than:
=20
push @status_options, 'hidden' if=20
GCt::glyph_attribute-?->retrieve(=20
glyph_type =3D> $glyph_type, =20
attr_name =3D> 'face_hideable'=20
)=20
-?->attr_value;
=20
Any feedback is appreciated.
=20
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<p class=3DMsoNormal><font size=3D2 face=3D"Courier New"><span =
style=3D'font-size:10.0pt;
font-family:"Courier New"'> We all know that simple =
scalars
can be chained together;<o:p></o:p></span></font></p>
<p class=3DMsoNormal><font size=3D2 face=3D"Courier New"><span =
style=3D'font-size:10.0pt;
font-family:"Courier New"'><o:p> </o:p></span></font></p>
<p class=3DMsoNormal><font size=3D2 face=3D"Courier New"><span =
style=3D'font-size:10.0pt;
font-family:"Courier New"'> $boolean =3D =
$this and
$that or $the_other;<o:p></o:p></span></font></p>
<p class=3DMsoNormal><font size=3D2 face=3D"Courier New"><span =
style=3D'font-size:10.0pt;
font-family:"Courier New"'><o:p> </o:p></span></font></p>
<p class=3DMsoNormal><font size=3D2 face=3D"Courier New"><span =
style=3D'font-size:10.0pt;
font-family:"Courier New"'> I'm sure many of you have =
used
Perl methods which return objects which<o:p></o:p></span></font></p>
<p class=3DMsoNormal><font size=3D2 face=3D"Courier New"><span =
style=3D'font-size:10.0pt;
font-family:"Courier New"'> you can use again in a =
chain like
so:<o:p></o:p></span></font></p>
<p class=3DMsoNormal><font size=3D2 face=3D"Courier New"><span =
style=3D'font-size:10.0pt;
font-family:"Courier New"'><o:p> </o:p></span></font></p>
<p class=3DMsoNormal><font size=3D2 face=3D"Courier New"><span =
style=3D'font-size:10.0pt;
font-family:"Courier New"'> push =
@status_options,
'hidden' if <o:p></o:p></span></font></p>
<p class=3DMsoNormal><font size=3D2 face=3D"Courier New"><span =
style=3D'font-size:10.0pt;
font-family:"Courier New"'>
GCt::glyph_attribute->retrieve( <o:p></o:p></span></font></p>
<p class=3DMsoNormal><font size=3D2 face=3D"Courier New"><span =
style=3D'font-size:10.0pt;
font-family:"Courier =
New"'>
glyph_type =3D> $glyph_type, <o:p></o:p></span></font></p>
<p class=3DMsoNormal><font size=3D2 face=3D"Courier New"><span =
style=3D'font-size:10.0pt;
font-family:"Courier =
New"'>
attr_name =3D> 'face_hideable' <o:p></o:p></span></font></p>
<p class=3DMsoNormal><font size=3D2 face=3D"Courier New"><span =
style=3D'font-size:10.0pt;
font-family:"Courier =
New"'>
) <o:p></o:p></span></font></p>
<p class=3DMsoNormal><font size=3D2 face=3D"Courier New"><span =
style=3D'font-size:10.0pt;
font-family:"Courier =
New"'>
->attr_value;<o:p></o:p></span></font></p>
<p class=3DMsoNormal><font size=3D2 face=3D"Courier New"><span =
style=3D'font-size:10.0pt;
font-family:"Courier New"'><o:p> </o:p></span></font></p>
<p class=3DMsoNormal><font size=3D2 face=3D"Courier New"><span =
style=3D'font-size:10.0pt;
font-family:"Courier New"'> It would be neat if there =
were
some method-chaining syntax/module which<o:p></o:p></span></font></p>
<p class=3DMsoNormal><font size=3D2 face=3D"Courier New"><span =
style=3D'font-size:10.0pt;
font-family:"Courier New"'> indicated "return =
false if
your method call returns false":<o:p></o:p></span></font></p>
<p class=3DMsoNormal><font size=3D2 face=3D"Courier New"><span =
style=3D'font-size:10.0pt;
font-family:"Courier New"'><o:p> </o:p></span></font></p>
<p class=3DMsoNormal><font size=3D2 face=3D"Courier New"><span =
style=3D'font-size:10.0pt;
font-family:"Courier New"'>
$object-?->method1-?->method2-?->method3<o:p></o:p></span></font=
></p>
<p class=3DMsoNormal><font size=3D2 face=3D"Courier New"><span =
style=3D'font-size:10.0pt;
font-family:"Courier New"'><o:p> </o:p></span></font></p>
<p class=3DMsoNormal><font size=3D2 face=3D"Courier New"><span =
style=3D'font-size:10.0pt;
font-family:"Courier New"'> One solution appears to be
Pipeline:<o:p></o:p></span></font></p>
<p class=3DMsoNormal><font size=3D2 face=3D"Courier New"><span =
style=3D'font-size:10.0pt;
font-family:"Courier New"'><o:p> </o:p></span></font></p>
<p class=3DMsoNormal><font size=3D2 face=3D"Courier New"><span =
style=3D'font-size:10.0pt;
font-family:"Courier =
New"'>
http://search.cpan.org/~rclamp/Pipeline-3.12/lib/Pipeline.pm<o:p></o:p></=
span></font></p>
<p class=3DMsoNormal><font size=3D2 face=3D"Courier New"><span =
style=3D'font-size:10.0pt;
font-family:"Courier New"'><o:p> </o:p></span></font></p>
<p class=3DMsoNormal><font size=3D2 face=3D"Courier New"><span =
style=3D'font-size:10.0pt;
font-family:"Courier New"'> What I currently do is =
wrap the
method chain in an eval block and check<o:p></o:p></span></font></p>
<p class=3DMsoNormal><font size=3D2 face=3D"Courier New"><span =
style=3D'font-size:10.0pt;
font-family:"Courier New"'> to see if a Boolean was =
set
within the block:<o:p></o:p></span></font></p>
<p class=3DMsoNormal><font size=3D2 face=3D"Courier New"><span =
style=3D'font-size:10.0pt;
font-family:"Courier New"'><o:p> </o:p></span></font></p>
<p class=3DMsoNormal><font size=3D2 face=3D"Courier New"><span =
style=3D'font-size:10.0pt;
font-family:"Courier New"'> =
{<o:p></o:p></span></font></p>
<p class=3DMsoNormal><font size=3D2 face=3D"Courier New"><span =
style=3D'font-size:10.0pt;
font-family:"Courier New"'> my =
$boolean;<o:p></o:p></span></font></p>
<p class=3DMsoNormal><font size=3D2 face=3D"Courier New"><span =
style=3D'font-size:10.0pt;
font-family:"Courier New"'><o:p> </o:p></span></font></p>
<p class=3DMsoNormal><font size=3D2 face=3D"Courier New"><span =
style=3D'font-size:10.0pt;
font-family:"Courier New"'> eval =
{<o:p></o:p></span></font></p>
<p class=3DMsoNormal><font size=3D2 face=3D"Courier New"><span =
style=3D'font-size:10.0pt;
font-family:"Courier New"'> =
$boolean
=3D <o:p></o:p></span></font></p>
<p class=3DMsoNormal><font size=3D2 face=3D"Courier New"><span =
style=3D'font-size:10.0pt;
font-family:"Courier =
New"'>
GCt::glyph_attribute->retrieve<o:p></o:p></span></font></p>
<p class=3DMsoNormal><font size=3D2 face=3D"Courier New"><span =
style=3D'font-size:10.0pt;
font-family:"Courier =
New"'> &=
nbsp;
( <o:p></o:p></span></font></p>
<p class=3DMsoNormal><font size=3D2 face=3D"Courier New"><span =
style=3D'font-size:10.0pt;
font-family:"Courier =
New"'> =
glyph_type
=3D> $glyph_type, <o:p></o:p></span></font></p>
<p class=3DMsoNormal><font size=3D2 face=3D"Courier New"><span =
style=3D'font-size:10.0pt;
font-family:"Courier =
New"'> &=
nbsp;
attr_name =3D> 'face_hideable' <o:p></o:p></span></font></p>
<p class=3DMsoNormal><font size=3D2 face=3D"Courier New"><span =
style=3D'font-size:10.0pt;
font-family:"Courier =
New"'> &=
nbsp;
) <o:p></o:p></span></font></p>
<p class=3DMsoNormal><font size=3D2 face=3D"Courier New"><span =
style=3D'font-size:10.0pt;
font-family:"Courier =
New"'> &=
nbsp;
->attr_value;<o:p></o:p></span></font></p>
<p class=3DMsoNormal><font size=3D2 face=3D"Courier New"><span =
style=3D'font-size:10.0pt;
font-family:"Courier New"'> =
}<o:p></o:p></span></font></p>
<p class=3DMsoNormal><font size=3D2 face=3D"Courier New"><span =
style=3D'font-size:10.0pt;
font-family:"Courier New"'> =
}<o:p></o:p></span></font></p>
<p class=3DMsoNormal><font size=3D2 face=3D"Courier New"><span =
style=3D'font-size:10.0pt;
font-family:"Courier New"'><o:p> </o:p></span></font></p>
<p class=3DMsoNormal><font size=3D2 face=3D"Courier New"><span =
style=3D'font-size:10.0pt;
font-family:"Courier New"'> push @status_options, =
'hidden' if
$boolean;<o:p></o:p></span></font></p>
<p class=3DMsoNormal><font size=3D2 face=3D"Courier New"><span =
style=3D'font-size:10.0pt;
font-family:"Courier New"'><o:p> </o:p></span></font></p>
<p class=3DMsoNormal><font size=3D2 face=3D"Courier New"><span =
style=3D'font-size:10.0pt;
font-family:"Courier New"'> but that is much wordier =
than:<o:p></o:p></span></font></p>
<p class=3DMsoNormal><font size=3D2 face=3D"Courier New"><span =
style=3D'font-size:10.0pt;
font-family:"Courier New"'><o:p> </o:p></span></font></p>
<p class=3DMsoNormal><font size=3D2 face=3D"Courier New"><span =
style=3D'font-size:10.0pt;
font-family:"Courier New"'> push =
@status_options,
'hidden' if <o:p></o:p></span></font></p>
<p class=3DMsoNormal><font size=3D2 face=3D"Courier New"><span =
style=3D'font-size:10.0pt;
font-family:"Courier New"'>
GCt::glyph_attribute-?->retrieve( <o:p></o:p></span></font></p>
<p class=3DMsoNormal><font size=3D2 face=3D"Courier New"><span =
style=3D'font-size:10.0pt;
font-family:"Courier =
New"'>
glyph_type =3D> $glyph_type, <o:p></o:p></span></font></p>
<p class=3DMsoNormal><font size=3D2 face=3D"Courier New"><span =
style=3D'font-size:10.0pt;
font-family:"Courier =
New"'>
attr_name =3D> 'face_hideable' <o:p></o:p></span></font></p>
<p class=3DMsoNormal><font size=3D2 face=3D"Courier New"><span =
style=3D'font-size:10.0pt;
font-family:"Courier =
New"'>
) <o:p></o:p></span></font></p>
<p class=3DMsoNormal><font size=3D2 face=3D"Courier New"><span =
style=3D'font-size:10.0pt;
font-family:"Courier =
New"'>
-?->attr_value;<o:p></o:p></span></font></p>
<p class=3DMsoNormal><font size=3D2 face=3D"Courier New"><span =
style=3D'font-size:10.0pt;
font-family:"Courier New"'><o:p> </o:p></span></font></p>
<p class=3DMsoNormal><font size=3D2 face=3D"Courier New"><span =
style=3D'font-size:10.0pt;
font-family:"Courier New"'> Any feedback is =
appreciated.<o:p></o:p></span></font></p>
<p class=3DMsoNormal><font size=3D2 face=3D"Courier New"><span =
style=3D'font-size:10.0pt;
font-family:"Courier New"'><o:p> </o:p></span></font></p>
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short-circuiting method conjunction?
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