arrays: add more modern array operation functions (#11488)
parent
9554470985
commit
0c0e28df6e
|
@ -162,8 +162,9 @@ pub struct WindowAttribute {
|
||||||
// get snapshots of the window of the given size sliding along array with the given step, where each snapshot is an array.
|
// get snapshots of the window of the given size sliding along array with the given step, where each snapshot is an array.
|
||||||
// - `size` - snapshot size
|
// - `size` - snapshot size
|
||||||
// - `step` - gap size between each snapshot, default is 1.
|
// - `step` - gap size between each snapshot, default is 1.
|
||||||
// example A: arrays.window([1, 2, 3, 4], size: 2) => [[1, 2], [2, 3], [3, 4]]
|
//
|
||||||
// example B: arrays.window([1, 2, 3, 4, 5, 6, 7, 8, 9, 10], size: 3, step: 2) => [[1, 2, 3], [3, 4, 5], [5, 6, 7], [7, 8, 9]]
|
// example A: `arrays.window([1, 2, 3, 4], size: 2)` => `[[1, 2], [2, 3], [3, 4]]`
|
||||||
|
// example B: `arrays.window([1, 2, 3, 4, 5, 6, 7, 8, 9, 10], size: 3, step: 2)` => `[[1, 2, 3], [3, 4, 5], [5, 6, 7], [7, 8, 9]]`
|
||||||
pub fn window<T>(list []T, attr WindowAttribute) [][]T {
|
pub fn window<T>(list []T, attr WindowAttribute) [][]T {
|
||||||
// allocate snapshot array
|
// allocate snapshot array
|
||||||
mut windows := [][]T{cap: list.len - attr.size + 1}
|
mut windows := [][]T{cap: list.len - attr.size + 1}
|
||||||
|
@ -180,3 +181,102 @@ pub fn window<T>(list []T, attr WindowAttribute) [][]T {
|
||||||
|
|
||||||
return windows
|
return windows
|
||||||
}
|
}
|
||||||
|
|
||||||
|
// sum up array, return nothing when array has no elements
|
||||||
|
// NOTICE: currently V has bug that cannot make sum function takes custom struct with + operator overloaded.
|
||||||
|
// which means you can only pass array of numbers for now.
|
||||||
|
// Future work: Fix generic operator overloading detection issue.
|
||||||
|
// usage: `arrays.sum<int>([1, 2, 3, 4, 5])?` => `15`
|
||||||
|
pub fn sum<T>(list []T) ?T {
|
||||||
|
if list.len == 0 {
|
||||||
|
return error('Cannot sum up array of nothing.')
|
||||||
|
} else {
|
||||||
|
mut head := list[0]
|
||||||
|
|
||||||
|
for i, e in list {
|
||||||
|
if i == 0 {
|
||||||
|
continue
|
||||||
|
} else {
|
||||||
|
head += e
|
||||||
|
}
|
||||||
|
}
|
||||||
|
|
||||||
|
return head
|
||||||
|
}
|
||||||
|
}
|
||||||
|
|
||||||
|
// accumulates values with the first element and applying providing operation to current accumulator value and each elements.
|
||||||
|
// if the array is empty, then returns error.
|
||||||
|
// usage: `arrays.reduce([1, 2, 3, 4, 5], fn (t1 int, t2 int) int { return t1 * t2 })?` => `120`
|
||||||
|
pub fn reduce<T>(list []T, reduce_op fn (t1 T, t2 T) T) ?T {
|
||||||
|
if list.len == 0 {
|
||||||
|
return error('Cannot reduce array of nothing.')
|
||||||
|
} else {
|
||||||
|
mut value := list[0]
|
||||||
|
|
||||||
|
for i, e in list {
|
||||||
|
if i == 0 {
|
||||||
|
continue
|
||||||
|
} else {
|
||||||
|
value = reduce_op(value, e)
|
||||||
|
}
|
||||||
|
}
|
||||||
|
|
||||||
|
return value
|
||||||
|
}
|
||||||
|
}
|
||||||
|
|
||||||
|
// accumulates values with providing initial value and applying providing operation to current accumulator value and each elements.
|
||||||
|
// usage: `arrays.fold<string, byte>(['H', 'e', 'l', 'l', 'o'], 0, fn (r int, t string) int { return r + t[0] })` => `149`
|
||||||
|
pub fn fold<T, R>(list []T, init R, fold_op fn (r R, t T) R) R {
|
||||||
|
mut value := init
|
||||||
|
|
||||||
|
for e in list {
|
||||||
|
value = fold_op(value, e)
|
||||||
|
}
|
||||||
|
|
||||||
|
return value
|
||||||
|
}
|
||||||
|
|
||||||
|
// flattens n + 1 dimensional array into n dimensional array
|
||||||
|
// usage: `arrays.flatten<int>([[1, 2, 3], [4, 5]])` => `[1, 2, 3, 4, 5]`
|
||||||
|
pub fn flatten<T>(list [][]T) []T {
|
||||||
|
// calculate required capacity
|
||||||
|
mut required_size := 0
|
||||||
|
|
||||||
|
for e1 in list {
|
||||||
|
for _ in e1 {
|
||||||
|
required_size += 1
|
||||||
|
}
|
||||||
|
}
|
||||||
|
|
||||||
|
// allocate flattened array
|
||||||
|
mut result := []T{cap: required_size}
|
||||||
|
|
||||||
|
for e1 in list {
|
||||||
|
for e2 in e1 {
|
||||||
|
result << e2
|
||||||
|
}
|
||||||
|
}
|
||||||
|
|
||||||
|
return result
|
||||||
|
}
|
||||||
|
|
||||||
|
// grouping list of elements with given key selector.
|
||||||
|
// usage: `arrays.assort<int, string>(['H', 'el', 'lo'], fn (v string) int { return v.len })` => `{1: ['H'], 2: ['el', 'lo']}`
|
||||||
|
pub fn group_by<K, V>(list []V, grouping_op fn (v V) K) map[K][]V {
|
||||||
|
mut result := map[K][]V{}
|
||||||
|
|
||||||
|
for v in list {
|
||||||
|
key := grouping_op(v)
|
||||||
|
|
||||||
|
// check if key exists, if not, then create a new array with matched value, otherwise append.
|
||||||
|
if key in result {
|
||||||
|
result[key] << v
|
||||||
|
} else {
|
||||||
|
result[key] = [v]
|
||||||
|
}
|
||||||
|
}
|
||||||
|
|
||||||
|
return result
|
||||||
|
}
|
||||||
|
|
|
@ -106,3 +106,60 @@ fn test_window() {
|
||||||
assert window<int>(x, size: 3, step: 2) == [[1, 2, 3], [3, 4, 5]]
|
assert window<int>(x, size: 3, step: 2) == [[1, 2, 3], [3, 4, 5]]
|
||||||
assert window<int>([]int{}, size: 2) == [][]int{}
|
assert window<int>([]int{}, size: 2) == [][]int{}
|
||||||
}
|
}
|
||||||
|
|
||||||
|
fn test_sum() {
|
||||||
|
x := [1, 2, 3, 4, 5]
|
||||||
|
|
||||||
|
assert sum<int>(x) or { 0 } == 15
|
||||||
|
assert sum<f64>([1.0, 2.5, 3.5, 4.0]) or { 0 } == 11.0
|
||||||
|
assert sum<int>([]int{}) or { 0 } == 0
|
||||||
|
}
|
||||||
|
|
||||||
|
fn test_reduce() {
|
||||||
|
x := [1, 2, 3, 4, 5]
|
||||||
|
|
||||||
|
assert reduce<int>(x, fn (t1 int, t2 int) int {
|
||||||
|
return t1 + t2
|
||||||
|
}) or { 0 } == 15
|
||||||
|
assert reduce<string>(['H', 'e', 'l', 'l', 'o'], fn (t1 string, t2 string) string {
|
||||||
|
return t1 + t2
|
||||||
|
}) or { '' } == 'Hello' // For the sake please use array's join instead.
|
||||||
|
assert reduce<int>([]int{}, fn (t1 int, t2 int) int {
|
||||||
|
return 0
|
||||||
|
}) or { -1 } == -1
|
||||||
|
}
|
||||||
|
|
||||||
|
fn test_fold() {
|
||||||
|
x := [1, 2, 3, 4, 5]
|
||||||
|
|
||||||
|
assert fold<int, int>(x, 5, fn (r int, t int) int {
|
||||||
|
return r + t
|
||||||
|
}) == 20
|
||||||
|
assert fold<string, int>(['H', 'e', 'l', 'l', 'l'], 0, fn (r int, t string) int {
|
||||||
|
return r + t[0]
|
||||||
|
}) == 497
|
||||||
|
assert fold<int, int>([]int{}, -1, fn (t1 int, t2 int) int {
|
||||||
|
return 0
|
||||||
|
}) == -1
|
||||||
|
}
|
||||||
|
|
||||||
|
fn test_flatten() {
|
||||||
|
x := [[1, 2, 3], [4, 5, 6]]
|
||||||
|
|
||||||
|
assert flatten<int>(x) == [1, 2, 3, 4, 5, 6]
|
||||||
|
assert flatten<int>([[]int{}]) == []
|
||||||
|
}
|
||||||
|
|
||||||
|
fn test_group_by() {
|
||||||
|
x := ['H', 'el', 'l', 'o ']
|
||||||
|
|
||||||
|
assert group_by<int, string>(x, fn (v string) int {
|
||||||
|
return v.len
|
||||||
|
}) == {
|
||||||
|
1: ['H', 'l']
|
||||||
|
2: ['el', 'o ']
|
||||||
|
}
|
||||||
|
assert group_by<int, int>([]int{}, fn (v int) int {
|
||||||
|
return 0
|
||||||
|
}) == map[int][]int{}
|
||||||
|
}
|
||||||
|
|
Loading…
Reference in New Issue