Learning Perl: 3.1. Accessing Elements of an Array

 

3.1. Accessing Elements of an Array If you've used arrays in another language,you won't be surprised to find Perl provides a way to subscript an array to refer to an element by a numeric index. The array elements are numbered using sequential integers,beginning at zero and increasing by one for each element,like this: @H_502_30@ $fred[0] = "yabba"; $fred[1] = "dabba"; $fred[2] = "doo"; The array name (in this case,"fred") is from a completely separate namespace than scalars use. You Could have a scalar variable named $fred in the same program. Perl treats them as different things and doesn't get confused.[*] (Your maintenance programmer might be confused though,so don't capricIoUsly make all of your variable names the same.) [*] The Syntax is always unambiguous; tricky perhaps,but unambiguous. You can use an array element like $fred[2] in every place[ ] where you Could use any other scalar variable like $fred. For example,you can get the value from an array element or change that value by the same sorts of expressions we used in the prevIoUs chapter: [ ] Well,almost. The most notable exception is that the control variable of a foreach loop,which you'll see later in this chapter,must be a simple scalar. And there are others,like the "indirect object slot" and "indirect filehandle slot" for print and printf. @H_502_30@ print $fred[0]; $fred[2] = "diddley"; $fred[1] .= "whatsis"; Of course,the subscript may be any expression that gives a numeric value. If it's not an integer,it'll automatically be truncated to the next lower integer: @H_502_30@ $number = 2.71828; print $fred[$number - 1]; # Same as printing $fred[1] If the subscript indicates an element that would be beyond the end of the array,the corresponding value will be undef. This is the same as ordinary scalars; if you've never stored a value into the variable,it's undef. @H_502_30@ $blank = $fred[ 142_857 ]; # unused array element gives undef $blanc = $mel; # unused scalar $mel also gives undef