An introduction to methods that let us observe lists and their elements
To get a specific element from a list, you
can use the method at(_), like this:
dialect "beginningStudent"
def animals = list("dog", "cat", "whale", "bird", "mouse")
print (animals.at 1)
print (animals at 4)
animals.at 1, returns "dog", and
animals.at 4, returns "bird".
size -> Number
// returns the number of elements in this list.
isEmpty -> Boolean
// returns true if this list is empty
first -> ElementType
// returns the first element of this list. It's an error to request this method on an empty list
last -> ElementType
// returns the last element of this list. It's an error to request this method on an empty list
at(n:Number) -> ElementType
// returns the n th element of this list. It's an error if n is not between 1 and the size of this list.
== (other) -> Boolean
// returns true if self and other contain the same elements, in the same order.
indices -> Sequence⟦Number⟧
// returns the sequence of this list's indices. So, if `xs.size` is 5,
// `xs.indices` is the sequence 1, 2, 3, 4, 5, which is written in Grace as `1..5`.
indexOf(sought:T) -> Number
// returns the index of the first element v in this list such that v == sought.
// Raises NoSuchObject exception if there is no such element.
indexOf⟦W⟧(sought:T) ifAbsent(action:Block) -> Number
// returns the index of the first element v in this list such that v == sought.
// In that way, it's just like indexOf(_). However, if there is no such
// element, this method executes the block of code action, and returns the
// resulting value.
Try out some of these methods by modifying this example code.