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Add Last Documentation #197

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merged 3 commits into from
Feb 4, 2018
Merged

Add Last Documentation #197

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2a9e2e8
corrections to First docs and add Last docs
Jan 31, 2018
8df70ae
address PR feedback for First and Last docs
Feb 1, 2018
5018c2a
some final PR feedback on isEven example
Feb 4, 2018
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12 changes: 6 additions & 6 deletions src/First/README.md
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Original file line number Diff line number Diff line change
Expand Up @@ -7,15 +7,15 @@ First a = First (Maybe a)
`First` is a `Monoid` that will always return the first, non-empty value when
(2) `First` instances are combined. `First` is able to be a `Monoid` because
it implements a `Maybe` under the hood. The use of the `Maybe` allows for an
[`empty`][#empty] `First` to be represented with a `Nothing`.
[`empty`](#empty) `First` to be represented with a `Nothing`.

`First` can be constructed with either a value or a `Maybe` instance. Any value
passed to the constructor will be wrapped in a `Just` to represent a non-empty
instance of `First`. Any `Maybe` passed to the constructor will be lifted as
is, allowing the ability to "choose" a value based on some disjunction.

While most `Monoid`s only provide a [`valueOf`](#valueof) function used for
extraction, `Last` takes advantage of its underlying `Maybe` to provide an
extraction, `First` takes advantage of its underlying `Maybe` to provide an
additional [`option`](#option) method. Using [`valueOf`](#valueof) will extract
the underlying `Maybe`, while [`option`](#option) will extract the underlying
value in the `Maybe`, using the provided default value when the underlying
Expand Down Expand Up @@ -131,7 +131,7 @@ a value in the case of an [`empty`](#empty) instance. Just like `option` on
a `Maybe` instance, it takes a value as its argument. When run on
an [`empty`](#empty) instance, the provided default will be returned.
If `option` is run on a non-empty instance however, the wrapped value will be
extracted not only from the `Last` but also from the underlying `Just`.
extracted not only from the `First` but also from the underlying `Just`.

If the underlying `Maybe` is desired, the [`valueOf`](#valueof) method can be
used and will return the `Maybe` instead.
Expand Down Expand Up @@ -366,7 +366,7 @@ const numVal = compose(
prop('val')
)

// numVal :: a -> First Number
// firstNumVal :: a -> First Number
const firstNumVal =
maybeToFirst(numVal)

Expand Down Expand Up @@ -438,10 +438,10 @@ const firstNum =

// "this is bad" is lost, mapped to Nothing
resultToFirst(Err('this is bad'))
//=> Nothing
//=> First( Nothing )

resultToFirst(Ok('this is great'))
//=> Just "this is great"
//=> First( Just "this is great" )

firstNum(90)
.concat(First(0))
Expand Down
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