Monads/Writer monad: Difference between revisions

=={{header|FreeBASIC}}==

{{trans|Go}}

<syntaxhighlight lang="vbnet">Type mwriter

value As Double

log_ As String

End Type

Function Unit(v As Double, s As String) As mwriter

Dim As mwriter mw

mw.value = v

mw.log_ = " " & s & ": " & Str(v) & Chr(10)

Return mw

End Function

Function Root(mw As mwriter) As mwriter

mw.value = Sqr(mw.value)

mw.log_ = mw.log_ & " Took square Root: " & Str(mw.value) & Chr(10)

Return mw

End Function

Function addOne(mw As mwriter) As mwriter

mw.value = mw.value + 1

mw.log_ = mw.log_ & " Added one : " & Str(mw.value) & Chr(10)

Return mw

End Function

Function Half(mw As mwriter) As mwriter

mw.value = mw.value / 2

mw.log_ = mw.log_ & " Divided by two : " & Str(mw.value) & Chr(10)

Return mw

End Function

Dim As mwriter mw1

mw1 = Unit(5, "Initial value ")

mw1 = Root(mw1)

mw1 = addOne(mw1)

mw1 = Half(mw1)

Print "The Golden Ratio is "; mw1.value

Print !"\nThis was derived as follows:-"

Print mw1.log_

Sleep</syntaxhighlight>

{{out}}

<pre>The Golden Ratio is 1.618033988749895

This was derived as follows:-

Initial value : 5

Took square Root: 2.23606797749979

Added one : 3.23606797749979

Divided by two : 1.618033988749895</pre>