Church numerals: Difference between revisions
Add Scala implementation
m (→{{header|Wren}}: Changed to Wren S/H) |
(Add Scala implementation) |
||
Line 3,616:
three ^ four = 81
four ^ three = 64</pre>
=={{header|Scala}}==
{{trans|Java}}
<syntaxhighlight lang="Scala">
object Church {
trait ChurchNum extends (ChurchNum => ChurchNum)
def zero: ChurchNum = f => x => x
def next(n: ChurchNum): ChurchNum = f => x => f(n(f)(x))
def plus(a: ChurchNum)(b: ChurchNum): ChurchNum = f => x => b(f)(a(f)(x))
def mult(a: ChurchNum)(b: ChurchNum): ChurchNum = f => x => b(a(f))(x)
def pow(m: ChurchNum)(n: ChurchNum): ChurchNum = n(m)
def toChurchNum(n: Int): ChurchNum = if (n <= 0) zero else next(toChurchNum(n - 1))
def toInt(c: ChurchNum): Int = {
var counter = 0
val funCounter: ChurchNum = f => { counter += 1; f }
plus(zero)(c)(funCounter)(x => x)
counter
}
def main(args: Array[String]): Unit = {
val zero = Church.zero
val three = next(next(next(zero)))
val four = next(next(next(next(zero))))
println(s"3+4=${toInt(plus(three)(four))}") // prints 7
println(s"4+3=${toInt(plus(four)(three))}") // prints 7
println(s"3*4=${toInt(mult(three)(four))}") // prints 12
println(s"4*3=${toInt(mult(four)(three))}") // prints 12
// exponentiation. note the reversed order!
println(s"3^4=${toInt(pow(four)(three))}") // prints 81
println(s"4^3=${toInt(pow(three)(four))}") // prints 64
println(s" 8=${toInt(toChurchNum(8))}") // prints 8
}
}
</syntaxhighlight>
{{out}}
<pre>
3+4=7
4+3=7
3*4=12
4*3=12
3^4=64
4^3=81
8=8
</pre>
=={{header|Standard ML}}==
<syntaxhighlight lang="standard ml">
| |||