Monads/Maybe monad: Difference between revisions
Added Wren
Thundergnat (talk | contribs) m (Promote to task, lots of examples, little controversy) |
(Added Wren) |
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Line 1,098:
#=> #<Maybe @value=nil>
</lang>
=={{header|Wren}}==
{{trans|Go}}
{{libheader|Wren-fmt}}
<lang ecmascript>import "/fmt" for Fmt
class Maybe {
construct new(value) {
_value = value
}
value { _value }
bind(f) { f.call(_value) }
static unit(i) { Maybe.new(i) }
}
var decrement = Fn.new { |i|
if (!i) return Maybe.unit(null)
return Maybe.unit(i - 1)
}
var triple = Fn.new { |i|
if (!i) return Maybe.unit(null)
return Maybe.unit(3 * i)
}
for (i in [3, 4, null, 5]) {
var m1 = Maybe.unit(i)
var m2 = m1.bind(decrement).bind(triple)
var s1 = (m1.value) ? "%(m1.value)" : "none"
var s2 = (m2.value) ? "%(m2.value)" : "none"
System.print("%(Fmt.s(4, s1)) -> %(s2)")
}</lang>
{{out}}
<pre>
3 -> 6
4 -> 9
none -> none
5 -> 12
</pre>
=={{header|zkl}}==
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