Scala equivalent of Python help()

Question

I'm proficient in Python but a noob at Scala. I'm about to write some dirty experiment code in Scala, and came across the thought that it would be really handy if Scala had a function like help() in Python. For example, if I wanted to see the built-in methods for a Scala Array I might want to type something like help(Array), just like I would type help(list) in Python. Does such a thing exist for Scala?

Answer 1

I do not know of one built-in but you should use Scaladocs to find the same information.

Unless you use eclipse which has an auto complete with short explanations. For instance it will give you all the commands for arrays after typing 'array.'.

Answer 2

I think tab completion is the closest thing to Python's help.

There is also a dated but still relevant post from @dcsobral on using Scala documentation and Scalex which is similar to Hoogle for Haskell.

This is the tab completion in the Object Array.

scala> Array.
apply                  asInstanceOf           canBuildFrom           concat                 copy                   
empty                  emptyBooleanArray      emptyByteArray         emptyCharArray         emptyDoubleArray       
emptyFloatArray        emptyIntArray          emptyLongArray         emptyObjectArray       emptyShortArray        
fallbackCanBuildFrom   fill                   isInstanceOf           iterate                newBuilder             
ofDim                  range                  tabulate               toString               unapplySeq   

This is for the methods on the class Array. Not sure why this doesn't show value members after a.

scala> val a = Array(1,2,3)
a: Array[Int] = Array(1, 2, 3)

scala> a.
apply          asInstanceOf   clone          isInstanceOf   length         toString       update  

Though a little daunting at times tab completion on a method shows the method signatures. Here it is for Array.fill

def fill[T](n1: Int, n2: Int)(elem: => T)(implicit evidence$10: reflect.ClassTag[T]): Array[Array[T]]                                                   
def fill[T](n1: Int, n2: Int, n3: Int)(elem: => T)(implicit evidence$11: reflect.ClassTag[T]): Array[Array[Array[T]]]                                   
def fill[T](n1: Int, n2: Int, n3: Int, n4: Int)(elem: => T)(implicit evidence$12: reflect.ClassTag[T]): Array[Array[Array[Array[T]]]]                   
def fill[T](n1: Int, n2: Int, n3: Int, n4: Int, n5: Int)(elem: => T)(implicit evidence$13: reflect.ClassTag[T]): Array[Array[Array[Array[Array[T]]]]]   
def fill[T](n: Int)(elem: => T)(implicit evidence$9: reflect.ClassTag[T]): Array[T]  

Answer 3

sbt-man is a sbt plugin for looking up scaladoc. The sbt console command starts the Scala REPL with project classes and dependencies on the classpath

Example:

man Traversable /:
[man] scala.collection.Traversable
[man] def /:[B](z: B)(op: (B ⇒ A ⇒ B)): B
[man] Applies a binary operator to a start value and all elements of this
collection, going left to right. Note: /: is alternate syntax for foldLeft;
z /: xs is the same as xs foldLeft z. Note: will not terminate for infinite-
sized collections. Note: might return different results for different runs,
unless the underlying collection type is ordered. or the operator is
associative and commutative. 

Answer 4

Similarly, IDEA has its "Quick Documentation Look-up" command, which works for Scala as well as Java (-Doc) JARs and source-code documentation comments.

Answer 5

In scala , you can try using the below ..( similar to the one we have in python )..

help(RDD1) in python will give you the rdd1 description with full details.

Scala > RDD1.[tab]

On hitting tab you will find the list of options available to the specified RDD1, similar option you find in eclipse .