Fixed a typo. (purescript-contrib#280)

Author: jbrains

text/chapter7.md

@@ -329,7 +329,7 @@ This might be good enough, but if we want to see a list of _all_ missing fields
 
 As an example of working with applicative functors abstractly, this section will show how to write a function which will generically combine side-effects encoded by an applicative functor `f`.
 
-What does this mean? Well, suppose we have a list of wrapped arguments of type `f a` for some `a`. That is, suppose we have an list of type `List (f a)`. Intuitively, this represents a list of computations with side-effects tracked by `f`, each with return type `a`. If we could run all of these computations in order, we would obtain a list of results of type `List a`. However, we would still have side-effects tracked by `f`. That is, we expect to be able to turn something of type `List (f a)` into something of type `f (List a)` by "combining" the effects inside the original list.
+What does this mean? Well, suppose we have a list of wrapped arguments of type `f a` for some `a`. That is, suppose we have a list of type `List (f a)`. Intuitively, this represents a list of computations with side-effects tracked by `f`, each with return type `a`. If we could run all of these computations in order, we would obtain a list of results of type `List a`. However, we would still have side-effects tracked by `f`. That is, we expect to be able to turn something of type `List (f a)` into something of type `f (List a)` by "combining" the effects inside the original list.
 
 For any fixed list size `n`, there is a function of `n` arguments which builds a list of size `n` out of those arguments. For example, if `n` is `3`, the function is `\x y z -> x : y : z : Nil`. This function has type `a -> a -> a -> List a`. We can use the `Applicative` instance for `List` to lift this function over `f`, to get a function of type `f a -> f a -> f a -> f (List a)`. But, since we can do this for any `n`, it makes sense that we should be able to perform the same lifting for any _list_ of arguments.