Perl uses special characters to indicate the type of variable that is being used
Each type of variable holds data in different ways
|Scalar||individual numbers, text, or references|
|Array||ordered lists of scalars|
|Hash||unordered lists of scalars|
|type of scalar||examples|
|number: integers||-1 1 101 0|
|number: floating-points||-0.1 0.1 100.1|
|string: letters||"a" "A" "Z" "z"|
|string: words||"Pickle" "tickle"|
|string: words and spaces and punctuation||"Over the sun and beyond the blue."|
|reference||See later lessons|
Arrays: Ordered list of scalars
|type of list||elements of list|
|list of numbers||-1,1,0.1,-0.01,101,0|
|list of strings||"a","Over the sun","z"|
|list of numbers and strings||"Pickle",0,"tickle","Over the sun",-42|
Elements of an ordered list or array can be accessed by using its position in the list or its INDEX.
- example array: (-1,1,0.1,-0.01,101,0)
- The list is ordered because each element has a position/index(number).
- The position is used to access a specific element
|second to last/-2||101|
Hash: Unordered list of scalars
|type of hash||elements of hash|
|list of numbers and strings||t => "tickle", 1 => "one" , "onehundred" => 100|
Elements of an unordered list or hash can be accessed, not using its position in the list but by its KEY.
- a KEY is like an INDEX but it can be any scalar not just a number.
- example unordered list or hash: (t => "tickle", 1 => "one" , "onehundred" => 100)
- The list is unordered because each element has a key(any scalar) not an ordered position
- The key is used to access a specific element.
|last||no last element since the list is unordered|
- What is the best variable type to store:
- A complete DNA sequence?
- Individual nucleotides of a DNA sequence that you want to keep in the appropriate order?
- Gene names and the corresponding DNA sequence?