Re: Re: Scala beginner question

>
> import scala.io.StdIn

val inputLines = Iterator continually StdIn.readLine() takeWhile (_ !=>
> null)
> for(line <- inputLines) { … }


I might be because I am still a Scala novel nonetheless I find this a bit
> hard to read, it does its job though.


Easy enough to explain!

import scala.io.StdIn

We use scala.io.StdIn for the StdIn.readLine() method, because readLine()
in predef is deprecated


Iterator continually StdIn.readLine() takeWhile (_ !=> null)

This is infix notation, it’s directly equivalent to:


Iterator.continually(StdIn.readLine()).takeWhile(_ !=> null)

Where:


Iterator.continually(expr)

returns an iterator (a potentially infinite, lazily
evaluated “collection”), where each element is generated on-demand by
evaluating expr.


Iterator continually StdIn.readLine()

Is one such iterator, with each element coming from a successive calls to
readLine()


someIterator takeWhile (_ !=> null)

Transforms someIterator, returning another iterator that terminates as soon
as a null element is encountered in the original
Therefore…


Iterator continually StdIn.readLine() takeWhile (_ !=> null)

Is an iterator that returns successive calls to readLine(), (each time you
call next(), or when you use foreach, or map, or flatMap, or use it in a
for-comprehension - which is just syntactic sugar for foreach, map or
flatMap) until there’s a null element




On 3 March 2016 at 18:59, Pietro <[email protected]> wrote:

> Kevin Wright <[email protected]> writes:
>
> > Numerous better ideas…
> >
> > 1. You’re making checks against two different regexes that can be
> > combined into one.
> > 2. You’re attempting to match “.” in one of those expressions. This
> > will match any character unless you escape it to a literal with “\.”
> > 3. Anything used in a pattern match should begin with an uppercase
> > letter
> >
> > Taking points 1,2,3 into consideration:
> >
> > val UnwantedChar = """[0-9]|\.|;|,|"|:""".r
> >
> > 4. You don’t need to supply the empty parameter block when calling
> > `toLowerCase`. By convention, this syntax is only used for methods
> > with side effects, not for simple getters or conversions
> > 5. You’re explicitly converting a String to a StringOps - This is
> > already done for you via the magic of implicits
> > 6. When pattern matching against a regex, it destructures the string
> > import scala.io.StdIn
> > val inputLines = Iterator continually StdIn.readLine() takeWhile (_ !=
> > null)
> > // note the () … because readLine() *is* side-effecting
> > for(line <- inputLines) {
> > …
> > }
> >
> I might be because I am still a Scala novel nonetheless I find this a bit
> hard to read, it does its job though.
>
> > 10. The `transformContent` method is now so short that it’s easier to
> > write the content inline
> > 11. Try to avoid side-effects in the middle of other blocks of code,
> > they’re better at the boundary of your app
> >
> > Putting it all together:
> >
> > import scala.io.StdIn
> > val UnwantedChar = """[0-9]|\.|;|,|"|:""".r
> > val inputLines = Iterator continually StdIn.readLine() takeWhile (_ !=
> > null)
> > val filteredInputLines = inputLines map {line =>
> > UnwantedChar.replaceAllIn(line.toLowerCase, "")
> > }
> > filteredInputLines foreach println
> >
> Thanks a lot, my previous solution was definitely a cumbersome solution.
>
>
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-- 
Kevin Wright
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"My point today is that, if we wish to count lines of code, we should not
regard them as "lines produced" but as "lines spent": the current
conventional wisdom is so foolish as to book that count on the wrong side
of the ledger" ~ Dijkstra

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