Talk:Scala (programming language): Difference between revisions

Revision as of 08:05, 12 February 2019

Revision as of 18:50, 11 May 2020

Line 251:

Here is ''modN'':

<sourcesyntaxhighlight lang="scala">

def modN(n: Int)(x: Int) = ((x % n) == 0)

</syntaxhighlight>

</source>

Here are the expressions that use ''modN'' to create a function argument:

<sourcesyntaxhighlight lang="scala">

println(filter(nums, modN(2)))

println(filter(nums, modN(3)))

</syntaxhighlight>

</source>

It is clear that we have a value binding, which is what happens for partial functions, not currying. [[User:Nxavar|Nxavar]] ([[User talk:Nxavar|talk]]) 18:15, 5 November 2014 (UTC)

Line 268:

::The example function in the book is:

<sourcesyntaxhighlight lang="scala">

def sum(f: Int => Int): (Int, Int) => Int = {

def sumF(a: Int, b: Int): Int =

Line 274:

sumF

}

</syntaxhighlight>

</source>

::It takes a function with one argument and it embeds it to another function which is then returned. The above example is not currying because the returned function is not a single argument function. However, it shows that Scala has syntactic support for currying.

Line 280:

::This is how a curried function for addition would look like in Scala:

<sourcesyntaxhighlight lang="scala">

def add(a: Int): (Int) => Int = {

def increment(b: Int): Int =

Line 288:

var c = add(5)(6) // c = 11

</syntaxhighlight>

</source>

::In conclusion, Scala supports currying, although none of the examples mentioned here are about currying. [[User:Nxavar|Nxavar]] ([[User talk:Nxavar|talk]]) 19:59, 5 November 2014 (UTC)

:::While there is a difference in Scala between

<sourcesyntaxhighlight lang="scala">

def foo1(a: Int)(b: Int): Int = a + b

def foo2(a: Int): (Int) => Int = (b: Int) => a + b

val foo3: Int => Int => Int = (a: Int) => (b: Int) => a + b

</syntaxhighlight>

</source>

for all these goes that

<sourcesyntaxhighlight lang="scala">

val c: Int = foo1(5)(6) //or foo2(5)(6) or foo3(5)(6)

</syntaxhighlight>

</source>

is perfectly legal and does what you expect. The difference shows up at

<sourcesyntaxhighlight lang="scala">

val tst1: Int => Int => Int = foo1 _

val tst2: Int => Int => Int = foo2 _

val tst3: Int => Int => Int = foo3

</syntaxhighlight>

</source>

where methods need eta expansion to be converted to functions. Technically speaking only foo3 is a (curried) function, the other two are methods. Calling foo2 a curried function, but not foo1 doesn't seem right. [[User:Martijn Hoekstra|Martijn Hoekstra]] ([[User talk:Martijn Hoekstra|talk]]) 14:48, 13 November 2014 (UTC)