mirror of
https://github.com/github/semantic.git
synced 2024-12-28 09:21:35 +03:00
98 lines
3.3 KiB
Swift
98 lines
3.3 KiB
Swift
public struct State<T> {
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public let rest: String
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public let value: T
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}
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public prefix func ^(string: String)(_ input: String) -> State<String>? {
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return input.characters.startsWith(string.characters)
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? State(rest: input.from(string.characters.count), value: string)
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: nil
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}
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public prefix func ^(strings: [String])(_ input: String) -> State<String>? {
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return strings.indexOf { input.characters.startsWith($0.characters) }
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.flatMap { index in
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let string = strings[index]
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return (^string)(input)
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}
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}
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public prefix func ^<S where S: SequenceType, S.Generator.Element == Character>(strings: S) -> String -> State<String>? {
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return ^strings.map { String($0) }
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}
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/// Parse the full string with parser or fail.
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public func full<A>(parser: String -> State<A>?)(_ input: String) -> A? {
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return parser(input).flatMap { $0.rest.isEmpty ? $0.value : nil }
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}
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/// A convenience for use while developing parsers.
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public func never<T>(_: String) -> State<T>? {
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return nil
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}
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//// Matches a single character that is not matched by `parser`.
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public func not<T>(parser: String -> State<T>?)(_ input: String) -> State<String>? {
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if input.isEmpty { return nil }
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return parser(input).map(const(nil)) ?? State(rest: input.from(1), value: input.to(1))
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}
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/// Delays evaluation of a parser.
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public func delay<A>(thunk: () -> String -> State<A>?) -> String -> State<A>? {
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return { thunk()($0) }
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}
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public func parseWhile(predicate: Character -> Bool)(_ input: String) -> State<String>? {
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return input.characters.count > 0 && predicate(input.characters[input.startIndex])
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? parseWhile(predicate)(input.from(1)).map { State(rest: $0.rest, value: input.to(1) + $0.value) } ?? State(rest: input.from(1), value: input.to(1))
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: nil
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}
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public postfix func * <T>(parser: String -> State<T>?) -> String -> State<[T]>? {
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return (Array.cons <^> (parser <*> { (parser*)($0) })) <|> pure([])
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}
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public postfix func + <T> (parser: String -> State<T>?) -> String -> State<[T]>? {
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return (Array.cons <^> (parser <*> parser*))
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}
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public func interpolate<Separator, Element>(element: String -> State<Element>?, _ separator: String -> State<Separator>?) -> String -> State<[Element]>? {
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return Array.cons <^> (element <*> (separator *> element)*) <|> pure([])
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}
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public func <*> <T, U> (left: String -> State<T>?, right: String -> State<U>?)(_ input: String) -> State<(T, U)>? {
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return left(input).flatMap { l in
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right(l.rest).map { r in
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State(rest: r.rest, value: (l.value, r.value))
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}
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}
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}
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public func <* <T, U> (left: String -> State<T>?, right: String -> State<U>?) -> String -> State<T>? {
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return left >>- { const($0) <^> right }
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}
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public func *> <T, U> (left: String -> State<T>?, right: String -> State<U>?) -> String -> State<U>? {
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return left >>- const(right)
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}
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public func <|> <T> (left: String -> State<T>?, right: String -> State<T>?)(_ input: String) -> State<T>? {
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return left(input) ?? right(input)
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}
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public func <^> <T, U> (left: T -> U, right: String -> State<T>?) -> String -> State<U>? {
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return right >>- { pure(left($0)) }
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}
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public func >>- <T, U> (left: String -> State<T>?, right: T -> String -> State<U>?)(_ input: String) -> State<U>? {
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return left(input).flatMap { state in right(state.value)(state.rest) }
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}
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public func pure<A>(value: A)(_ input: String) -> State<A>? {
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return State(rest: input, value: value)
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}
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