example/test: add a binary search tree example and test (#8145)

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Ruofan XU 2021-01-19 21:18:38 +08:00 committed by GitHub
parent 5067046538
commit 103901a5cb
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2 changed files with 195 additions and 18 deletions

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@ -0,0 +1,106 @@
// Binary Search Tree example by @SleepyRoy
// TODO: make Node.value generic once it's robust enough
// TODO: `return match` instead of returns everywhere inside match
struct Empty {}
struct Node {
value f64
left Tree
right Tree
}
type Tree = Empty | Node
// return size(number of nodes) of BST
fn size(tree Tree) int {
return match tree {
// TODO: remove int() once match gets smarter
Empty { int(0) }
Node { 1 + size(tree.left) + size(tree.right) }
}
}
// insert a value to BST
fn insert(tree Tree, x f64) Tree {
match tree {
Empty { return Node{x, tree, tree} }
Node {
return if x == tree.value {
tree
} else if x < tree.value {
Node{...tree, left: insert(tree.left, x)}
} else {
Node{...tree, right: insert(tree.right, x)}
}
}
}
}
// whether able to find a value in BST
fn search(tree Tree, x f64) bool {
match tree {
Empty { return false }
Node {
return if x == tree.value {
true
} else if x < tree.value {
search(tree.left, x)
} else {
search(tree.right, x)
}
}
}
}
// find the minimal value of a BST
fn min(tree Tree) f64 {
match tree {
Empty { return 1e100 }
Node { return if tree.value < min(tree.left) { tree.value } else { min(tree.left) } }
}
}
// delete a value in BST (if nonexist do nothing)
fn delete(tree Tree, x f64) Tree {
match tree {
Empty { return tree }
Node {
if tree.left is Node && tree.right is Node {
return if x < tree.value {
Node{...tree, left: delete(tree.left, x)}
} else if x > tree.value {
Node{...tree, right: delete(tree.right, x)}
} else {
Node{...tree, value: min(tree.right), right: delete(tree.right, min(tree.right))}
}
} else if tree.left is Node {
return if x == tree.value { tree.left } else { Node{...tree, left: delete(tree.left, x)} }
} else {
if x == tree.value { return tree.right } else { return Node{...tree, right: delete(tree.right, x)} }
}
}
}
}
fn main() {
mut tree := Tree(Empty{})
input := [0.3, 0.2, 0.5, 0.0, 0.6, 0.8, 0.9, 1.0, 0.1, 0.4, 0.7]
for i in input {
tree = insert(tree, i)
}
println('[1] after insertion tree size is ${size(tree)}') // 11
del := [-0.3, 0.0, 0.3, 0.6, 1.0, 1.5]
for i in del {
tree = delete(tree, i)
}
print('[2] after deletion tree size is ${size(tree)}, ') // 7
print('and these elements were deleted: ') // 0.0 0.3 0.6 1.0
for i in input {
if !search(tree, i) {
print('$i ')
}
}
println('')
}

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@ -1,6 +1,6 @@
type Expr = IfExpr | IntegerLiteral
type Stmt = FnDecl | StructDecl
type Node = Expr | Stmt
type ExprStmt = Expr | Stmt
struct FnDecl {
pos int
@ -540,38 +540,109 @@ fn handle(e Expr) string {
return ''
}
// for a binary tree
// Binary Search Tree test by @SleepyRoy
// TODO: make Node.value generic once it's robust enough
// TODO: `return match` instead of returns everywhere inside match
struct Empty {}
struct Node_ {
// TODO: make value generic once it's more robust
struct Node {
value f64
left Tree
right Tree
}
type Tree = Empty | Node_
type Tree = Empty | Node
// return size(number of nodes) of BST
fn size(tree Tree) int {
return match tree {
// TODO: remove int() here once match gets smarter
// TODO: remove int() once match gets smarter
Empty { int(0) }
Node_ { 1 + size(tree.left) + size(tree.right) }
Node { 1 + size(tree.left) + size(tree.right) }
}
}
fn sum(tree Tree) f64 {
return match tree {
// TODO: remove f64() here once match gets smarter
Empty { f64(0) }
Node_ { tree.value + sum(tree.left) + sum(tree.right) }
// insert a value to BST
fn insert(tree Tree, x f64) Tree {
match tree {
Empty { return Node{x, tree, tree} }
Node {
return if x == tree.value {
tree
} else if x < tree.value {
Node{...tree, left: insert(tree.left, x)}
} else {
Node{...tree, right: insert(tree.right, x)}
}
}
}
}
fn test_binary_tree_operation() {
left := Node_{0.2, Empty{}, Empty{}}
right := Node_{0.3, Empty{}, Node_{0.4, Empty{}, Empty{}}}
tree := Node_{0.5, left, right}
assert size(tree) == 4
assert sum(tree) == 1.4
// whether able to find a value in BST
fn search(tree Tree, x f64) bool {
match tree {
Empty { return false }
Node {
return if x == tree.value {
true
} else if x < tree.value {
search(tree.left, x)
} else {
search(tree.right, x)
}
}
}
}
// find the minimal value of a BST
fn min(tree Tree) f64 {
match tree {
Empty { return 1e100 }
Node { return if tree.value < min(tree.left) { tree.value } else { min(tree.left) } }
}
}
// delete a value in BST (if nonexist do nothing)
fn delete(tree Tree, x f64) Tree {
match tree {
Empty { return tree }
Node {
if tree.left is Node && tree.right is Node {
return if x < tree.value {
Node{...tree, left: delete(tree.left, x)}
} else if x > tree.value {
Node{...tree, right: delete(tree.right, x)}
} else {
Node{...tree, value: min(tree.right), right: delete(tree.right, min(tree.right))}
}
} else if tree.left is Node {
return if x == tree.value { tree.left } else { Node{...tree, left: delete(tree.left, x)} }
} else {
if x == tree.value { return tree.right } else { return Node{...tree, right: delete(tree.right, x)} }
}
}
}
}
fn test_binary_search_tree() {
mut tree := Tree(Empty{})
input := [0.3, 0.2, 0.5, 0.0, 0.6, 0.8, 0.9, 1.0, 0.1, 0.4, 0.7]
for i in input {
tree = insert(tree, i)
}
assert size(tree) == 11
del := [-0.3, 0.0, 0.3, 0.6, 1.0, 1.5]
for i in del {
tree = delete(tree, i)
}
assert size(tree) == 7
mut deleted := []f64{ }
for i in input {
if !search(tree, i) {
deleted << i
}
}
deleted.sort()
assert deleted == [0.0, 0.3, 0.6, 1.0]
}