Regarding :: there is another Stackoverflow entry which covers the :: case. In short, it is used to construct Lists by 'consing' a head element and a tail list. It is both a class which represents a cons'ed list and which can be used as an extractor, but most commonly it is a method on a list. As Pablo Fernandez points out, since it ends in a colon, it is right associative, meaning the receiver of the method call is to the right, and the argument to the left of the operator. That way you can elegantly express the consing as prepending a new head element to an existing list:

val x = 2 :: 3 :: Nil  // same result as List(2, 3)
val y = 1 :: x         // yields List(1, 2, 3)

这相当于

val x = Nil.::(3).::(2) // successively prepend 3 and 2 to an empty list
val y = x.::(1)         // then prepend 1

作为提取器对象的用法如下:

def extract(l: List[Int]) = l match {
   case Nil          => "empty"
   case head :: Nil  => "exactly one element (" + head + ")"
   case head :: tail => "more than one element"
}

extract(Nil)          // yields "empty"
extract(List(1))      // yields "exactly one element (1)"
extract(List(2, 3))   // yields "more than one element"

这看起来像一个运算符，但它实际上只是另一种(更可读的)书写方式

def extract2(l: List[Int]) = l match {
   case Nil            => "empty"
   case ::(head, Nil)  => "exactly one element (" + head + ")"
   case ::(head, tail) => "more than one element"
}

你可以在这篇文章中阅读更多关于提取器的信息。

Scala继承了Java的大部分算术运算符。这包括位-或|(单个管道字符)、位-和&、位-异-或^，以及逻辑(boolean)或||(两个管道字符)和逻辑-和&&。有趣的是，你可以在布尔上使用单字符操作符，所以java的逻辑操作符是完全多余的:

true && true   // valid
true & true    // valid as well

3 & 4          // bitwise-and (011 & 100 yields 000)
3 && 4         // not valid

正如在另一篇文章中指出的那样，以等号=结尾的调用将通过重赋来解析(如果该名称不存在!):

var x = 3
x += 1         // `+=` is not a method in `int`, Scala makes it `x = x + 1`

这种“双重检查”使得可以轻松地将可变集合转换为不可变集合:

val m = collection.mutable.Set("Hallo")   // `m` a val, but holds mutable coll
var i = collection.immutable.Set("Hallo") // `i` is a var, but holds immutable coll

m += "Welt" // destructive call m.+=("Welt")
i += "Welt" // re-assignment i = i + "Welt" (creates a new immutable Set)

<=就像你会“读”它:'小于或等于'。所以它是一个数学运算符，在<(小于?)、>(大于?)、==(等于?)、!=(不等于?)、<=(小于或等于?)和>=(大于或等于?)的列表中。

这不能与=>混淆，后者是一种右向双箭头，用于将参数列表与函数体分离，并将模式匹配中的测试条件(case块)与匹配发生时执行的函数体分离。你可以在我之前的两个回答中看到这样的例子。一、函数使用:

coll.map(tup => tup._2.reverse)

它已经被缩写为省略了类型。接下来的函数是

// function arguments         function body
(tup: Tuple2[Int, String]) => tup._2.reverse

与模式匹配使用:

def extract2(l: List[Int]) = l match {
   // if l matches Nil    return "empty"
   case Nil            => "empty"
   // etc.
   case ::(head, Nil)  => "exactly one element (" + head + ")"
   // etc.
   case ::(head, tail) => "more than one element"
}

所以你想要一个详尽的答案?这里有一个有趣的，希望完整的，相当长的列表给你:)

http://jim-mcbeath.blogspot.com/2008/12/scala-operator-cheat-sheet.html

(免责声明-这篇文章写于2008年，所以可能有点过时)

!! AbstractActor
!! Actor // Sends msg to this actor and immediately ...
!! Proxy
! Actor // Sends msg to this actor (asynchronous).
! Channel // Sends a message to this Channel.
! OutputChannel // Sends msg to this ...
! Proxy // Sends msg to this ...
!= Any // o != arg0 is the same as !(o == (arg0)).
!= AnyRef
!= Boolean
!= Byte
!= Char
!= Double
!= Float
!= Int
!= Long
!= Short
!? AbstractActor
!? Actor // Sends msg to this actor and awaits reply ...
!? Channel // Sends a message to this Channel and ...
!? Proxy
% BigInt // Remainder of BigInts
% Byte
% Char
% Double
% Float
% Int
% Long
% Short
% Elem // Returns a new element with updated attributes, resolving namespace uris from this element's scope. ...
&&& Parsers.Parser
&& Boolean
&+ NodeBuffer // Append given object to this buffer, returns reference on this NodeBuffer ...
& BigInt // Bitwise and of BigInts
& Boolean
& Byte
& Char
& Enumeration.Set32 // Equivalent to * for bit sets. ...
& Enumeration.Set64 // Equivalent to * for bit sets. ...
& Enumeration.SetXX // Equivalent to * for bit sets. ...
& Int
& Long
& Short
&~ BigInt // Bitwise and-not of BigInts. Returns a BigInt whose value is (this & ~that).
&~ Enumeration.Set32 // Equivalent to - for bit sets. ...
&~ Enumeration.Set64 // Equivalent to - for bit sets. ...
&~ Enumeration.SetXX // Equivalent to - for bit sets. ...
>>> Byte
>>> Char
>>> Int
>>> Long
>>> Short
>> BigInt // (Signed) rightshift of BigInt
>> Byte
>> Char
>> Int
>> Long
>> Short
>> Parsers.Parser // Returns into(fq)
>> Parsers.Parser // Returns into(fq)
> BigDecimal // Greater-than comparison of BigDecimals
> BigInt // Greater-than comparison of BigInts
> Byte
> Char
> Double
> Float
> Int
> Long
> Ordered
> PartiallyOrdered
> Short
>= BigDecimal // Greater-than-or-equals comparison of BigDecimals
>= BigInt // Greater-than-or-equals comparison of BigInts
>= Byte
>= Char
>= Double
>= Float
>= Int
>= Long
>= Ordered
>= PartiallyOrdered
>= Short
<< BigInt // Leftshift of BigInt
<< Byte
<< Char
<< Int
<< Long
<< Short
<< Buffer // Send a message to this scriptable object.
<< BufferProxy // Send a message to this scriptable object.
<< Map // Send a message to this scriptable object.
<< MapProxy // Send a message to this scriptable object.
<< Scriptable // Send a message to this scriptable object.
<< Set // Send a message to this scriptable object.
<< SetProxy // Send a message to this scriptable object.
<< SynchronizedBuffer // Send a message to this scriptable object.
<< SynchronizedMap // Send a message to this scriptable object.
<< SynchronizedSet // Send a message to this scriptable object.
< BigDecimal // Less-than of BigDecimals
< BigInt // Less-than of BigInts
< Byte
< Char
< Double
< Float
< Int
< Long
< Ordered
< PartiallyOrdered
< Short
< OffsetPosition // Compare this position to another, by first comparing their line numbers, ...
< Position // Compare this position to another, by first comparing their line numbers, ...
<= BigDecimal // Less-than-or-equals comparison of BigDecimals
<= BigInt // Less-than-or-equals comparison of BigInts
<= Byte
<= Char
<= Double
<= Float
<= Int
<= Long
<= Ordered
<= PartiallyOrdered
<= Short
<~ Parsers.Parser // A parser combinator for sequential composition which keeps only the left result
** Enumeration.SetXX
** Set // Intersect. It computes an intersection with set that. ...
** Set // This method is an alias for intersect. ...
* BigDecimal // Multiplication of BigDecimals
* BigInt // Multiplication of BigInts
* Byte
* Char
* Double
* Float
* Int
* Long
* Short
* Set
* RichString // return n times the current string
* Parsers.Parser // Returns a parser that repeatedly parses what this parser parses, interleaved with the `sep' parser. ...
* Parsers.Parser // Returns a parser that repeatedly parses what this parser parses
* Parsers.Parser // Returns a parser that repeatedly parses what this parser parses, interleaved with the `sep' parser. ...
* Parsers.Parser // Returns a parser that repeatedly parses what this parser parses, interleaved with the `sep' parser.
* Parsers.Parser // Returns a parser that repeatedly parses what this parser parses
++: ArrayBuffer // Prepends a number of elements provided by an iterable object ...
++: Buffer // Prepends a number of elements provided by an iterable object ...
++: BufferProxy // Prepends a number of elements provided by an iterable object ...
++: SynchronizedBuffer // Prepends a number of elements provided by an iterable object ...
++ Array // Returns an array consisting of all elements of this array followed ...
++ Enumeration.SetXX
++ Iterable // Appends two iterable objects.
++ IterableProxy // Appends two iterable objects.
++ Iterator // Returns a new iterator that first yields the elements of this ...
++ List // Appends two list objects.
++ RandomAccessSeq // Appends two iterable objects.
++ RandomAccessSeqProxy // Appends two iterable objects.
++ Seq // Appends two iterable objects.
++ SeqProxy // Appends two iterable objects.
++ IntMap // Add a sequence of key/value pairs to this map.
++ LongMap // Add a sequence of key/value pairs to this map.
++ Map // Add a sequence of key/value pairs to this map.
++ Set // Add all the elements provided by an iterator ...
++ Set // Add all the elements provided by an iterator to the set.
++ SortedMap // Add a sequence of key/value pairs to this map.
++ SortedSet // Add all the elements provided by an iterator ...
++ Stack // Push all elements provided by the given iterable object onto ...
++ Stack // Push all elements provided by the given iterator object onto ...
++ TreeHashMap
++ TreeHashMap // Add a sequence of key/value pairs to this map.
++ Collection // Operator shortcut for addAll.
++ Set // Operator shortcut for addAll.
++ ArrayBuffer // Appends two iterable objects.
++ Buffer // Appends a number of elements provided by an iterable object ...
++ Buffer // Appends a number of elements provided by an iterator ...
++ Buffer // Appends two iterable objects.
++ BufferProxy // Appends a number of elements provided by an iterable object ...
++ Map // Add a sequence of key/value pairs to this map.
++ MapProxy // Add a sequence of key/value pairs to this map.
++ PriorityQueue
++ Set // Add all the elements provided by an iterator ...
++ SynchronizedBuffer // Appends a number of elements provided by an iterable object ...
++ RichString // Appends two iterable objects.
++ RichStringBuilder // Appends a number of elements provided by an iterable object ...
++ RichStringBuilder // Appends two iterable objects.
++= Map // Add a sequence of key/value pairs to this map.
++= MapWrapper // Add a sequence of key/value pairs to this map.
++= ArrayBuffer // Appends a number of elements in an array
++= ArrayBuffer // Appends a number of elements provided by an iterable object ...
++= ArrayStack // Pushes all the provided elements onto the stack.
++= Buffer // Appends a number of elements in an array
++= Buffer // Appends a number of elements provided by an iterable object ...
++= Buffer // Appends a number of elements provided by an iterator
++= BufferProxy // Appends a number of elements provided by an iterable object ...
++= Map // Add a sequence of key/value pairs to this map.
++= MapProxy // Add a sequence of key/value pairs to this map.
++= PriorityQueue // Adds all elements provided by an Iterable object ...
++= PriorityQueue // Adds all elements provided by an iterator into the priority queue.
++= PriorityQueueProxy // Adds all elements provided by an Iterable object ...
++= PriorityQueueProxy // Adds all elements provided by an iterator into the priority queue.
++= Queue // Adds all elements provided by an Iterable object ...
++= Queue // Adds all elements provided by an iterator ...
++= QueueProxy // Adds all elements provided by an Iterable object ...
++= QueueProxy // Adds all elements provided by an iterator ...
++= Set // Add all the elements provided by an iterator ...
++= SetProxy // Add all the elements provided by an iterator ...
++= Stack // Pushes all elements provided by an Iterable object ...
++= Stack // Pushes all elements provided by an iterator ...
++= StackProxy // Pushes all elements provided by an Iterable object ...
++= StackProxy // Pushes all elements provided by an iterator ...
++= SynchronizedBuffer // Appends a number of elements provided by an iterable object ...
++= SynchronizedMap // Add a sequence of key/value pairs to this map.
++= SynchronizedPriorityQueue // Adds all elements provided by an Iterable object ...
++= SynchronizedPriorityQueue // Adds all elements provided by an iterator into the priority queue.
++= SynchronizedQueue // Adds all elements provided by an Iterable object ...
++= SynchronizedQueue // Adds all elements provided by an iterator ...
++= SynchronizedSet // Add all the elements provided by an iterator ...
++= SynchronizedStack // Pushes all elements provided by an Iterable object ...
++= SynchronizedStack // Pushes all elements provided by an iterator ...
++= RichStringBuilder // Appends a number of elements provided by an iterable object ...
+: ArrayBuffer // Prepends a single element to this buffer and return ...
+: Buffer // Prepend a single element to this buffer and return ...
+: BufferProxy // Prepend a single element to this buffer and return ...
+: ListBuffer // Prepends a single element to this buffer. It takes constant ...
+: ObservableBuffer // Prepend a single element to this buffer and return ...
+: SynchronizedBuffer // Prepend a single element to this buffer and return ...
+: RichStringBuilder // Prepend a single element to this buffer and return ...
+: BufferWrapper // Prepend a single element to this buffer and return ...
+: RefBuffer // Prepend a single element to this buffer and return ...
+ BigDecimal // Addition of BigDecimals
+ BigInt // Addition of BigInts
+ Byte
+ Char
+ Double
+ Enumeration.SetXX // Create a new set with an additional element.
+ Float
+ Int
+ List
+ Long
+ Short
+ EmptySet // Create a new set with an additional element.
+ HashSet // Create a new set with an additional element.
+ ListSet.Node // This method creates a new set with an additional element.
+ ListSet // This method creates a new set with an additional element.
+ Map
+ Map // Add a key/value pair to this map.
+ Map // Add two or more key/value pairs to this map.
+ Queue // Creates a new queue with element added at the end ...
+ Queue // Returns a new queue with all all elements provided by ...
+ Set // Add two or more elements to this set.
+ Set // Create a new set with an additional element.
+ Set1 // Create a new set with an additional element.
+ Set2 // Create a new set with an additional element.
+ Set3 // Create a new set with an additional element.
+ Set4 // Create a new set with an additional element.
+ SortedMap // Add a key/value pair to this map.
+ SortedMap // Add two or more key/value pairs to this map.
+ SortedSet // Create a new set with an additional element.
+ Stack // Push all elements provided by the given iterable object onto ...
+ Stack // Push an element on the stack.
+ TreeSet // A new TreeSet with the entry added is returned,
+ Buffer // adds "a" from the collection. Useful for chaining.
+ Collection // adds "a" from the collection. Useful for chaining.
+ Map // Add a key/value pair to this map.
+ Set // adds "a" from the collection. Useful for chaining.
+ Buffer // Append a single element to this buffer and return ...
+ BufferProxy // Append a single element to this buffer and return ...
+ Map // Add a key/value pair to this map.
+ Map // Add two or more key/value pairs to this map.
+ MapProxy // Add a key/value pair to this map.
+ MapProxy // Add two or more key/value pairs to this map.
+ ObservableBuffer // Append a single element to this buffer and return ...
+ PriorityQueue
+ Set // Add a new element to the set.
+ Set // Add two or more elements to this set.
+ SynchronizedBuffer // Append a single element to this buffer and return ...
+ Parsers.Parser // Returns a parser that repeatedly (at least once) parses what this parser parses.
+ Parsers.Parser // Returns a parser that repeatedly (at least once) parses what this parser parses.
+= Collection // adds "a" from the collection.
+= Map // Add a key/value pair to this map.
+= ArrayBuffer // Appends a single element to this buffer and returns ...
+= ArrayStack // Alias for push.
+= BitSet // Sets i-th bit to true. ...
+= Buffer // Append a single element to this buffer.
+= BufferProxy // Append a single element to this buffer.
+= HashSet // Add a new element to the set.
+= ImmutableSetAdaptor // Add a new element to the set.
+= JavaSetAdaptor // Add a new element to the set.
+= LinkedHashSet // Add a new element to the set.
+= ListBuffer // Appends a single element to this buffer. It takes constant ...
+= Map // Add a key/value pair to this map.
+= Map // Add two or more key/value pairs to this map.
+= Map // This method defines syntactic sugar for adding or modifying ...
+= MapProxy // Add a key/value pair to this map.
+= MapProxy // Add two or more key/value pairs to this map.
+= ObservableSet // Add a new element to the set.
+= PriorityQueue // Add two or more elements to this set.
+= PriorityQueue // Inserts a single element into the priority queue.
+= PriorityQueueProxy // Inserts a single element into the priority queue.
+= Queue // Inserts a single element at the end of the queue.
+= QueueProxy // Inserts a single element at the end of the queue.
+= Set // Add a new element to the set.
+= Set // Add two or more elements to this set.
+= SetProxy // Add a new element to the set.
+= Stack // Pushes a single element on top of the stack.
+= StackProxy // Pushes a single element on top of the stack.
+= SynchronizedBuffer // Append a single element to this buffer.
+= SynchronizedMap // Add a key/value pair to this map.
+= SynchronizedMap // Add two or more key/value pairs to this map.
+= SynchronizedPriorityQueue // Inserts a single element into the priority queue.
+= SynchronizedQueue // Inserts a single element at the end of the queue.
+= SynchronizedSet // Add a new element to the set.
+= SynchronizedStack // Pushes a single element on top of the stack.
+= RichStringBuilder // Append a single element to this buffer.
+= Reactions // Add a reaction.
+= RefBuffer // Append a single element to this buffer.
+= CachedFileStorage // adds a node, setting this.dirty to true as a side effect
+= IndexedStorage // adds a node, setting this.dirty to true as a side effect
+= SetStorage // adds a node, setting this.dirty to true as a side effect
-> Map.MapTo
-> Map.MapTo
-- List // Computes the difference between this list and the given list ...
-- Map // Remove a sequence of keys from this map
-- Set // Remove all the elements provided by an iterator ...
-- SortedMap // Remove a sequence of keys from this map
-- MutableIterable // Operator shortcut for removeAll.
-- Set // Operator shortcut for removeAll.
-- Map // Remove a sequence of keys from this map
-- MapProxy // Remove a sequence of keys from this map
-- Set // Remove all the elements provided by an iterator ...
--= Map // Remove a sequence of keys from this map
--= MapProxy // Remove a sequence of keys from this map
--= Set // Remove all the elements provided by an iterator ...
--= SetProxy // Remove all the elements provided by an iterator ...
--= SynchronizedMap // Remove a sequence of keys from this map
--= SynchronizedSet // Remove all the elements provided by an iterator ...
- BigDecimal // Subtraction of BigDecimals
- BigInt // Subtraction of BigInts
- Byte
- Char
- Double
- Enumeration.SetXX // Remove a single element from a set.
- Float
- Int
- List // Computes the difference between this list and the given object ...
- Long
- Short
- EmptyMap // Remove a key from this map
- EmptySet // Remove a single element from a set.
- HashMap // Remove a key from this map
- HashSet // Remove a single element from a set.
- IntMap // Remove a key from this map
- ListMap.Node // Creates a new mapping without the given key. ...
- ListMap // This creates a new mapping without the given key. ...
- ListSet.Node // - can be used to remove a single element from ...
- ListSet // - can be used to remove a single element from ...
- LongMap // Remove a key from this map
- Map // Remove a key from this map
- Map // Remove two or more keys from this map
- Map1 // Remove a key from this map
- Map2 // Remove a key from this map
- Map3 // Remove a key from this map
- Map4 // Remove a key from this map
- Set // Remove a single element from a set.
- Set // Remove two or more elements from this set.
- Set1 // Remove a single element from a set.
- Set2 // Remove a single element from a set.
- Set3 // Remove a single element from a set.
- Set4 // Remove a single element from a set.
- SortedMap // Remove a key from this map
- SortedMap // Remove two or more keys from this map
- TreeHashMap // Remove a key from this map
- TreeMap // Remove a key from this map
- TreeSet // Remove a single element from a set.
- UnbalancedTreeMap.Node // Remove a key from this map
- UnbalancedTreeMap // Remove a key from this map
- Map // Remove a key from this map
- MutableIterable
- Set
- ListBuffer // Removes a single element from the buffer and return ...
- Map // Remove a key from this map
- Map // Remove two or more keys from this map
- MapProxy // Remove a key from this map
- MapProxy // Remove two or more keys from this map
- Set // Remove a new element from the set.
- Set // Remove two or more elements from this set.
-= Buffer // removes "a" from the collection.
-= Collection // removes "a" from the collection.
-= Map // Remove a key from this map, noop if key is not present.
-= BitSet // Clears the i-th bit.
-= Buffer // Removes a single element from this buffer, at its first occurrence. ...
-= HashMap // Remove a key from this map, noop if key is not present.
-= HashSet // Removes a single element from a set.
-= ImmutableMapAdaptor // Remove a key from this map, noop if key is not present.
-= ImmutableSetAdaptor // Removes a single element from a set.
-= JavaMapAdaptor // Remove a key from this map, noop if key is not present.
-= JavaSetAdaptor // Removes a single element from a set.
-= LinkedHashMap // Remove a key from this map, noop if key is not present.
-= LinkedHashSet // Removes a single element from a set.
-= ListBuffer // Remove a single element from this buffer. It takes linear time ...
-= Map // Remove a key from this map, noop if key is not present.
-= Map // Remove two or more keys from this map
-= MapProxy // Remove a key from this map, noop if key is not present.
-= MapProxy // Remove two or more keys from this map
-= ObservableMap // Remove a key from this map, noop if key is not present.
-= ObservableSet // Removes a single element from a set.
-= OpenHashMap // Remove a key from this map, noop if key is not present.
-= Set // Remove two or more elements from this set.
-= Set // Removes a single element from a set.
-= SetProxy // Removes a single element from a set.
-= SynchronizedMap // Remove a key from this map, noop if key is not present.
-= SynchronizedMap // Remove two or more keys from this map
-= SynchronizedSet // Removes a single element from a set.
-= Reactions // Remove the given reaction.
-= CachedFileStorage // removes a tree, setting this.dirty to true as a side effect
-= IndexedStorage // removes a tree, setting this.dirty to true as a side effect
/% BigInt // Returns a pair of two BigInts containing (this / that) and (this % that).
/: Iterable // Similar to foldLeft but can be used as ...
/: IterableProxy // Similar to foldLeft but can be used as ...
/: Iterator // Similar to foldLeft but can be used as ...
/ BigDecimal // Division of BigDecimals
/ BigInt // Division of BigInts
/ Byte
/ Char
/ Double
/ Float
/ Int
/ Long
/ Short
:/: Document
::: List
:: List
:: Document
:\ Iterable // An alias for foldRight. ...
:\ IterableProxy // An alias for foldRight. ...
:\ Iterator // An alias for foldRight. ...
== Any // o == arg0 is the same as o.equals(arg0).
== AnyRef // o == arg0 is the same as if (o eq null) arg0 eq null else o.equals(arg0).
== Boolean
== Byte
== Char
== Double
== Float
== Int
== Long
== Short
? Actor // Receives the next message from this actor's mailbox.
? Channel // Receives the next message from this Channel.
? InputChannel // Receives the next message from this Channel.
? Parsers.Parser // Returns a parser that optionally parses what this parser parses.
? Parsers.Parser // Returns a parser that optionally parses what this parser parses.
\ NodeSeq // Projection function. Similar to XPath, use this \ "foo"
\\ NodeSeq // projection function. Similar to XPath, use this \\ 'foo
^ BigInt // Bitwise exclusive-or of BigInts
^ Boolean
^ Byte
^ Char
^ Int
^ Long
^ Short
^? Parsers.Parser // A parser combinator for partial function application
^? Parsers.Parser // A parser combinator for partial function application
^^ Parsers.Parser // A parser combinator for function application
^^ Parsers.Parser // A parser combinator for function application
^^ Parsers.UnitParser // A parser combinator for function application
^^^ Parsers.Parser
| BigInt // Bitwise or of BigInts
| Boolean
| Byte
| Char
| Enumeration.Set32 // Equivalent to ++ for bit sets. Returns a set ...
| Enumeration.Set32 // Equivalent to + for bit sets. Returns a set ...
| Enumeration.Set64 // Equivalent to ++ for bit sets. Returns a set ...
| Enumeration.Set64 // Equivalent to + for bit sets. Returns a set ...
| Enumeration.SetXX // Equivalent to ++ for bit sets. Returns a set ...
| Enumeration.SetXX // Equivalent to + for bit sets. Returns a set ...
| Int
| Long
| Short
| Parsers.Parser // A parser combinator for alternative composition
| Parsers.Parser // A parser combinator for alternative composition
| Parsers.UnitParser // A parser combinator for alternative composition
|| Boolean
||| Parsers.Parser
||| Parsers.Parser // A parser combinator for alternative with longest match composition
||| Parsers.Parser // A parser combinator for alternative with longest match composition
||| Parsers.UnitParser // A parser combinator for alternative with longest match composition
~! Parsers.Parser // A parser combinator for non-back-tracking sequential composition
~! Parsers.Parser // A parser combinator for non-back-tracking sequential composition with a unit-parser
~! Parsers.Parser // A parser combinator for non-back-tracking sequential composition
~! Parsers.UnitParser // A parser combinator for non-back-tracking sequential composition with a unit-parser
~! Parsers.UnitParser // A parser combinator for non-back-tracking sequential composition
~> Parsers.Parser // A parser combinator for sequential composition which keeps only the right result
~ BigInt // Returns the bitwise complement of this BigNum
~ Parsers.OnceParser // A parser combinator for sequential composition
~ Parsers.Parser // A parser combinator for sequential composition
~ Parsers
~ Parsers.OnceParser // A parser combinator for sequential composition with a unit-parser
~ Parsers.OnceParser // A parser combinator for sequential composition
~ Parsers.Parser // A parser combinator for sequential composition with a unit-parser
~ Parsers.Parser // A parser combinator for sequential composition
~ Parsers.UnitOnceParser // A parser combinator for sequential composition with a unit-parser
~ Parsers.UnitOnceParser // A parser combinator for sequential composition
~ Parsers.UnitParser // A parser combinator for sequential composition with a unit-parser
~ Parsers.UnitParser // A parser combinator for sequential composition
unary_! Boolean
unary_+ Byte
unary_+ Char
unary_+ Double
unary_+ Float
unary_+ Int
unary_+ Long
unary_+ Short
unary_- BigDecimal // Returns a BigDecimal whose value is the negation of this BigDecimal
unary_- BigInt // Returns a BigInt whose value is the negation of this BigInt
unary_- Byte
unary_- Char
unary_- Double
unary_- Float
unary_- Int
unary_- Long
unary_- Short
unary_~ Byte
unary_~ Char
unary_~ Int
unary_~ Long
unary_~ Short

Regarding :: there is another Stackoverflow entry which covers the :: case. In short, it is used to construct Lists by 'consing' a head element and a tail list. It is both a class which represents a cons'ed list and which can be used as an extractor, but most commonly it is a method on a list. As Pablo Fernandez points out, since it ends in a colon, it is right associative, meaning the receiver of the method call is to the right, and the argument to the left of the operator. That way you can elegantly express the consing as prepending a new head element to an existing list:

val x = 2 :: 3 :: Nil  // same result as List(2, 3)
val y = 1 :: x         // yields List(1, 2, 3)

这相当于

val x = Nil.::(3).::(2) // successively prepend 3 and 2 to an empty list
val y = x.::(1)         // then prepend 1

作为提取器对象的用法如下:

def extract(l: List[Int]) = l match {
   case Nil          => "empty"
   case head :: Nil  => "exactly one element (" + head + ")"
   case head :: tail => "more than one element"
}

extract(Nil)          // yields "empty"
extract(List(1))      // yields "exactly one element (1)"
extract(List(2, 3))   // yields "more than one element"

这看起来像一个运算符，但它实际上只是另一种(更可读的)书写方式

def extract2(l: List[Int]) = l match {
   case Nil            => "empty"
   case ::(head, Nil)  => "exactly one element (" + head + ")"
   case ::(head, tail) => "more than one element"
}

你可以在这篇文章中阅读更多关于提取器的信息。

我认为现代IDE对于理解大型scala项目至关重要。由于这些操作符也是方法，在intellij思想中，我只是控制-单击或控制-b进入定义。

你可以右键点击一个cons操作符(::)，然后在scala javadoc中说“在这个列表的开头添加一个元素”。在用户定义的操作符中，这一点变得更加关键，因为它们可能被定义为很难找到的隐式…你的IDE知道隐式的定义在哪里。