Arrays

Instance methods on arrays. All methods support chaining.

Methods

Method	Returns	Description
len()	int	Element count
push(val)		Append element
pop()	int	Remove and return last
first()	int	First element
last()	int	Last element
min()	int	Minimum value
max()	int	Maximum value
sum()	int	Sum of all elements
slice(start, end)	array	Sub-array
sort()	array	Sorted copy
reverse()	array	Reversed copy
unique()	array	Deduplicated copy
concat(other)	array	Concatenate arrays
join(sep)	string	Join with separator
index_of(val)	int	Find element (-1 if missing)
remove(idx)		Remove at index
insert(idx, val)		Insert at index
map(fn)	array	Transform elements
filter(fn)	array	Filter elements
reduce(fn, init)	int	Fold elements
each(fn)		Call fn for each element
any(fn)	int	Any element matches (1/0)
every(fn)	int	All elements match (1/0)
sort_by(cmp_fn)		Sort with comparator

Indexing and Slicing

Index from the front with a[i], or from the back with a negative index - a[-1] is the last element:

a = [10, 20, 30, 40]
print(a[0].to_string())    // 10
print(a[-1].to_string())   // 40 - last
print(a[-2].to_string())   // 30 - second to last

Slice with a[i:j]. Either bound can be omitted:

a = [10, 20, 30, 40, 50]
head = a[:2]             // [10, 20]      - first two
tail = a[2:]             // [30, 40, 50]  - from index 2
mid  = a[1:4]            // [20, 30, 40]
copy = a[:]              // full copy

print(tail[-1].to_string())  // 50 - negative index works on slices too

Membership: in

Test whether an array contains a value with in / not in:

langs = ["python", "go", "rust"]
if "go" in langs { print("go supported") }
if "java" not in langs { print("no java") }

Method Chaining

// Chain any combination of array methods
result = [3, 1, 4, 1, 5, 9].sort().reverse()
print(result[0].to_string())  // 9

count = [5, 3, 1, 4, 2].filter(fn(x: int) -> bool { return x > 2 }).sort().len()
print(count.to_string())  // 3

words = "hello world foo".split(" ").sort().join(", ")
print(words)  // foo, hello, world

Functional

var doubled = nums.map(fn(x: int) -> int { return x * 2 })
var big = nums.filter(fn(x: int) -> bool { return x > 3 })
var total = nums.reduce(fn(acc: int, x: int) -> int { return acc + x }, 0)

Comprehensions

squares = [x * x for x in 0..10]
evens = [x for x in 0..20 if x % 2 == 0]

See Also

• Strings - .join() arrays into strings
• Log - structured logging
• HashMap - key-value alternative to arrays
• Control Flow - for-in loops over arrays