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Top Forums Shell Programming and Scripting Perl - Parentheses & Context confusion Post 302374928 by summer_cherry on Thursday 26th of November 2009 01:22:55 AM
Old 11-26-2009
Perl - Parentheses & Context confusion

Hi Expert,

Could you please explain why below two perl code get different result?

Thanks a lot.

Code:
sub test{
	return (2,3,4,5,6,3,4,50);
}

($a,$b)=(test)[1,4]; # 3,6

($a,$b)=test[1,4]; # 2,3

 

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Graph(3pm)						User Contributed Perl Documentation						Graph(3pm)

NAME
SVG::Graph - Visualize your data in Scalable Vector Graphics (SVG) format. SYNOPSIS
use SVG::Graph; use SVG::Graph::Data; use SVG::Graph::Data::Datum; #create a new SVG document to plot in... my $graph = SVG::Graph->new(width=>600,height=>600,margin=>30); #and create a frame to hold the data/glyphs my $frame = $graph->add_frame; #let's plot y = x^2 my @data = map {SVG::Graph::Data::Datum->new(x=>$_,y=>$_^2)} (1,2,3,4,5); my $data = SVG::Graph::Data->new(data => @data); #put the xy data into the frame $frame->add_data($data); #add some glyphs to apply to the data in the frame $frame->add_glyph('axis', #add an axis glyph 'x_absolute_ticks' => 1, #with ticks every one #unit on the x axis 'y_absolute_ticks' => 1, #and ticks every one #unit on the y axis 'stroke' => 'black', #draw the axis black 'stroke-width' => 2, #and 2px thick ); $frame->add_glyph('scatter', #add a scatterplot glyph 'stroke' => 'red', #the dots will be outlined #in red, 'fill' => 'red', #filled red, 'fill-opacity' => 0.5, #and 50% opaque ); #print the graphic print $graph->draw; DESCRIPTION
SVG::Graph is a suite of perl modules for plotting data. SVG::Graph currently supports plots of one-, two- and three-dimensional data, as well as N-ary rooted trees. Data may be represented as: Glyph Name Dimensionality supported 1d 2d 3d tree -------------------------------------------------------- Axis x Bar Graph x Bubble Plot x Heatmap Graph x Line Graph x Pie Graph x Scatter Plot x Spline Graph x Tree x SVG::Graph 0.02 is a pre-alpha release. Keep in mind that many of the glyphs are not very robust. PLOTTING
You need to create a SVG::Graph::Frame instance from the parent SVG::Graph instance for each set of data to be plotted. Datasets can be hierarchical, and to represent this, SVG::Graph::Frame instances can themselves contain subframes. SVG::Graph::Frame can contain: - multiple subframes as instances of SVG::Graph::Frame - a single SVG::Graph::Data instance - multiple SVG::Graph::Glyph instances with which to render the attached SVG::Graph::Data instance, and all SVG::Graph::Data instances attached to SVG::Graph::Frame subinstances See SVG::Graph::Frame and SVG::Graph::Glyph for details. ONE DATA SET 1. create an SVG::Graph instance 2. create an SVG::Graph::Frame instance by calling SVG::Graph::add_frame(); 3. create an SVG::Graph::Data instance, containing an SVG::Graph::Data::Datum instance for each data point. 4. Attach the SVG::Graph::Data instance to your SVG::Graph::Frame using SVG::Graph::Frame::add_data(); 5. Attach glyphs to the SVG::Graph::Frame instance using SVG::Graph::Frame::add_glyph(); 6. Call SVG::Graph::draw(); MULTIPLE DATA SETS 1. create an SVG::Graph instance 2. create an SVG::Graph::Frame instance by calling SVG::Graph::add_frame(); 3. create an SVG::Graph::Data instance, containing an SVG::Graph::Data::Datum instance for each data point. 4. Attach the SVG::Graph::Data instance to your SVG::Graph::Frame using SVG::Graph::Frame::add_data(); 5. Attach glyphs to the SVG::Graph::Frame instance using SVG::Graph::Frame::add_glyph(); 6. repeat [2-5] for each additional data set to be added. add_frame() can be called on SVG::Graph to add top-level data sets, or SVG::Graph::Frame to add hierarchical data sets. 7. Call SVG::Graph::draw(); FEEDBACK
Send an email to the svg-graph-developers list. For more info, visit the project page at http://www.sf.net/projects/svg-graph AUTHORS
Allen Day, <allenday@ucla.edu> Chris To, <crsto@ucla.edu> CONTRIBUTORS
James Chen, <chenj@seas.ucla.edu> Brian O'Connor, <boconnor@ucla.edu> SEE ALSO
SVG METHODS
new Title : new Usage : my $graph = SVG::Graph->new(width=>600, height=>600, margin=>20); Function: creates a new SVG::Graph object Returns : a SVG::Graph object Args : width => the width of the SVG height => the height of the SVG margin => margin for the root frame init Title : init Usage : Function: Example : Returns : Args : width Title : width Usage : $obj->width($newval) Function: Example : Returns : value of width (a scalar) Args : on set, new value (a scalar or undef, optional) height Title : height Usage : $obj->height($newval) Function: Example : Returns : value of height (a scalar) Args : on set, new value (a scalar or undef, optional) margin Title : margin Usage : $obj->margin($newval) Function: Example : Returns : value of margin (a scalar) Args : on set, new value (a scalar or undef, optional) svg Title : svg Usage : $obj->svg($newval) Function: Example : Returns : value of svg (a scalar) Args : on set, new value (a scalar or undef, optional) add_frame Title : add_frame Usage : my $frame = $graph->add_frame Function: adds a Frame to the current Graph Returns : a SVG::Graph::Frame object Args : a hash. usable keys: frame_transform (optional) 'top' default orientation 'bottom' rotates graph 180 deg (about the center) 'right' points top position towards right 'left' points top position towards left frames Title : frames Usage : get/set Function: Example : Returns : Args : xoffset Title : xoffset Usage : $obj->xoffset($newval) Function: Example : Returns : value of xoffset (a scalar) Args : on set, new value (a scalar or undef, optional) yoffset Title : yoffset Usage : $obj->yoffset($newval) Function: Example : Returns : value of yoffset (a scalar) Args : on set, new value (a scalar or undef, optional) draw Title : draw Usage : $graph=>draw Function: depends on child glyph implementations Returns : xmlifyied SVG object Args : none perl v5.10.0 2009-01-07 Graph(3pm)
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