perl - How to use an array reference to pairs of elements -

i considering answer uses single array reference of points, point reference two-element array. original code of question (function extract-crossing) uses 2 separate arrays $x , $y here call this:

my @x = @{ $_[0] }; @y = @{ $_[1] }; ... return extract_crossing(\@x, \@y); 

the new code below based on answer takes (x, y) , returns single datatype, here x intercept points:

use strict; use warnings;     use math::geometry::planar qw(segmentlineintersection); use test::exception;  sub x_intercepts {    ($points) = @_;     die 'must pass @ least 2 points' unless @$points >= 2;     @intercepts;    @x_axis = ( [0, 0], [1, 0] );     foreach $i (0 .. $#$points - 1) {      $intersect = segmentlineintersection([@$points[$i,$i+1],@x_axis]);      push @intercepts, $intersect if $intersect;    }     return \@intercepts; } 

which try call this:

my @x = @{ $_[0] }; @y = @{ $_[1] };   ... $masi = x_intercepts(\@x); return $masi;  

however, code not make sense. confused passing "double array" x_intercepts() function.

how can make example code clearer original setting?

if understanding problem here, @thissuitisblacknot++ has written function (x_intercepts available in thread: function extract intersections of crossing lines on axes) expects argument reference list of array references. x_intercepts subroutine in turn uses function math::geometry::planar expects points of line segment passed series of array references/anonymous arrays contain x,y values each point.

again - not entirely clear - seems your data in 2 different arrays: 1 containing x values , 1 corresponding y values. case? if not correct please leave comment , remove answer.

if source of problem can "munge" or transform data before pass x_intercepts or - @thissuitisblacknot suggests - can rewrite function. here example of munging existing data "@input_list" pass x_intercepts.

my @xs = qw/-1 1 3/; @ys = qw/-1 1 -1 /;  @input_list ; foreach $i ( 0..$#ys ) {    push @input_list,  [ $xs[$i], $ys[$i] ]  ; }  $intercept_list = x_intercepts(\@input_list)  ; join ",", @$_ @$intercept_list ; 

adding lines above script produces:

output:

0,0 2,0 

you have careful doing kind of thing , using tests make sure passing correctly transformed data in expected way idea.

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i think more general difficulty until familiar perl tricky see sorts of values subroutine expecting, end after passed in, , how access them.

a solid grasp of perl data structures can - example think calling "double array" or "double element" here "array of arrays". there ways make easier see default arguments passed subroutine (in @_) going (notice how @thissuitisblacknot has passed them nicely named array reference: "($points)"). copious re-reading of perldocperbsub can things seem more obvious.

references key understanding perl subroutines since pass array or hash subrouting need references. if argument passed x_intercepts list of 2 lists of anonymous arrays when assigned ($points), @$points->[0] @$points->[1] arrays contain lists.

i hope helps , not basic (or incorrect). if @thissuitisblacknot finds time provide answer should accept it: useful examples have been provided.