Created
October 27, 2016 10:31
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enum Block { | |
case code(code: String) | |
case text(String) | |
case header(String) | |
} | |
enum PlaygroundElement { | |
case code(String) | |
case documentation([Block]) | |
} | |
func playground(blocks: [Block]) -> [PlaygroundElement] { | |
// We want to generate a playground from an array of `Block` elements. | |
// | |
// Separate the code from the documentation. | |
// All the consecutive non-code should be grouped together. | |
} | |
// The following input: | |
let sample: [Block] = [.code("swift sample code"), .header("My Header"), .text("Hello"), .code("more"), .text("text")] | |
// Should return the following result: | |
let result: [PlaygroundElement] = [ | |
.code("swift sample code"), | |
.documentation[.header("My Header"), .text("Hello")] | |
.code("more"), | |
.documentation[.text("text")] | |
] |
enum Block {
case code(code: String)
case text(String)
case header(String)
var playgroundElement: PlaygroundElement {
switch self {
case .code(let value):
return .code(value)
case .text:
return .documentation([self])
case .header:
return .documentation([self])
}
}
}
enum PlaygroundElement {
case code(String)
case documentation([Block])
func combineDocumentation(element: PlaygroundElement) -> [PlaygroundElement] {
guard let elementValue = element.documentValue() else { return [self, element] }
guard let documentValue = documentValue() else { return [self, element] }
return [.documentation(documentValue + elementValue)]
}
func documentValue() -> [Block]? {
switch self {
case .documentation(let value):
return value
default:
return nil
}
}
}
func playground(blocks: [Block]) -> [PlaygroundElement] {
return blocks.reduce([]) { (result, block) -> [PlaygroundElement] in
let playgroundElement = block.playgroundElement
guard result.count > 0 else { return [playgroundElement] }
var mutableA = result
let last = mutableA.removeLast()
mutableA.appendContentsOf(last.combineDocumentation(playgroundElement))
return mutableA
}
}
let sample: [Block] = [.code(code: "swift sample code"), .header("My Header"), .text("Hello"), .code(code: "more"), .text("text")]
let result = playground(sample)
let a = result[0]
let b = result[1]
let c = result[2]
let d = result[3]
My take:
enum Block {
case code(String)
case text(String)
case header(String)
}
enum PlaygroundElement {
case code(String)
case documentation([Block])
}
func playground(blocks: [Block]) -> [PlaygroundElement] {
func flush(_ buffer: [Block]) -> [PlaygroundElement] {
return buffer.isEmpty ? [] : [.documentation(buffer)]
}
typealias Accum = (elements: [PlaygroundElement], buffer: [Block])
let r = blocks.reduce(Accum([], [])) { (acc: Accum, block: Block) -> Accum in
switch block {
case .code(let code):
return Accum(acc.elements + flush(acc.buffer) + [.code(code)], [])
case .text, .header:
return Accum(acc.elements, acc.buffer + [block])
}
}
return r.elements + flush(r.buffer)
}
// The following input:
let sample: [Block] = [
.code("swift sample code"), .header("My Header"), .text("Hello"), .code("more code"), .code("code"), .text("text")
]
// Should return the following result:
let expected: [PlaygroundElement] = [
.code("swift sample code"),
.documentation([.header("My Header"), .text("Hello")]),
.code("more"),
.code("code"),
.documentation([.text("text")])
]
let result = playground(blocks: sample)
print(result)
print(expected)
[EDIT] Removed the useless lazy
before reduce
(I added it while trying other solutions where it made sense… before settling on this one)
Another variation:
func playground(blocks: [Block]) -> [PlaygroundElement] {
return blocks.reduce([]) { (acc, block) in
switch block {
case .code(let code):
return acc + [.code(code)]
case .text, .header:
if case .documentation(let blocks)? = acc.last {
return acc.dropLast() + [.documentation(blocks + [block])]
} else {
return acc + [.documentation([block])]
}
}
}
}
Agreed that using reduce
with value types might not be very efficient, but in this case I find FP nicer than using mutability — and the solution with mutability has already been proposed by @nicklockwood on Twitter 😉
It'd be easy if we had this useful function in the standard library.
extension Block {
var isCode: Bool {
if case .code = self { return true } else { return false }
}
}
func playground(blocks: [Block]) -> [PlaygroundElement] {
return blocks.cut { $0.isCode || $1.isCode }.map {
if case .code(let value) = $0.first! {
assert($0.count == 1)
return .code(value)
} else {
return .documentation(Array($0))
}
}
}
func playground(blocks: [Block]) -> [PlaygroundElement] {
return blocks.reduce([]) { res, block in
switch (res.last, block) {
case (_, .code(let code)):
return res + [.code(code)]
case (.some(.documentation(let blocks)), _):
return res.dropLast() + [.documentation(blocks + [block])]
default:
return res + [.documentation([block])]
}
}
}
First I did:
func playground(blocks: [Block]) -> [PlaygroundElement] {
var playground = [PlaygroundElement]()
for block in blocks {
let ele: PlaygroundElement
if case let .code(s) = block {
ele = .code(s)
} else if case let .documentation(existingDocBlocks)? = playground.last {
playground.removeLast()
ele = .documentation(existingDocBlocks + [block])
} else {
ele = .documentation([block])
}
playground.append(ele)
}
return playground
}
but I saw it looked quite like another suggestion, and I didn't like removing the last element from the array, so I tried another way:
extension Block {
var shouldBeClassedAsDocumentation: Bool {
switch self {
case .code: return false
default: return true
}
}
}
func playground(blocks: [Block]) -> [PlaygroundElement] {
var playground = [PlaygroundElement]()
for var idx in 0..<blocks.endIndex {
let ele: PlaygroundElement
if case let .code(s) = blocks[idx] {
ele = .code(s)
} else {
let docEndIndex = blocks[idx..<blocks.endIndex].index { !$0.shouldBeClassedAsDocumentation }
let docBlocks = Array(blocks[idx..<(docEndIndex ?? blocks.endIndex)])
idx += docBlocks.count + 1
ele = .documentation(docBlocks)
}
playground.append(ele)
}
return playground
}
Using indirectEnums and also without mutating the original structs
import Foundation
enum Block {
case code(String)
case text(String)
case header(String)
}
enum PlaygroundElement {
case code(String)
case documentation([Block])
}
indirect enum PlaygroundBlock {
case code(String, PlaygroundBlock?)
case documentation([Block], PlaygroundBlock?)
init(block: Block, parent: PlaygroundBlock? = nil) {
switch block {
case let .code(value):
self = .code(value, parent)
default:
self = .documentation([block], parent)
}
}
mutating func process(block: Block)-> PlaygroundBlock {
switch (self, block) {
case (.code, _):
return PlaygroundBlock(block: block, parent: self)
case (.documentation, .code):
return PlaygroundBlock(block: block, parent: self)
case (.documentation(let (values, parent)), _):
var newValues = [block]
newValues.append(contentsOf: values)
self = .documentation(newValues, parent)
return self
}
}
func flatMap()-> [PlaygroundElement] {
switch self {
case let .code(value, parent):
var items: [PlaygroundElement] = [.code(value)]
if let parent = parent {
items.append(contentsOf: parent.flatMap())
}
return items
case let .documentation(values, parent):
var items: [PlaygroundElement] = [.documentation(values)]
if let parent = parent {
items.append(contentsOf: parent.flatMap())
}
return items
}
}
}
func playground(blocks: [Block]) -> [PlaygroundElement] {
var consumableBlocks: [Block] = blocks
guard let lastBlock = consumableBlocks.popLast() else { return [] }
var lastLine = PlaygroundBlock(block: lastBlock)
while let nextBlock = consumableBlocks.popLast() {
lastLine = lastLine.process(block: nextBlock)
}
return lastLine.flatMap()
}
let sample: [Block] = [.code("swift sample code"), .header("My Header"), .text("Hello"), .code("more"), .text("text")]
let results = playground(blocks: sample)
results.count == 4
print(results)
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First idea that came to my mind:
Using
append
instead of returning arrays wih+
, because compile time ¯_(ツ)_/¯