Fix typos and article use, reword phrases in "Composing Suspending functions"

Author: Yanis Batura

docs/composing-suspending-functions.md

@@ -56,9 +56,9 @@ suspend fun doSomethingUsefulTwo(): Int {
 </div>
 
 
-What do we do if need to invoke them _sequentially_ -- first `doSomethingUsefulOne` _and then_ 
-`doSomethingUsefulTwo` and compute the sum of their results? 
-In practice we do this if we use the results of the first function to make a decision on whether we need 
+What do we do if we need them to be invoked _sequentially_ &mdash; first `doSomethingUsefulOne` _and then_ 
+`doSomethingUsefulTwo`, and compute the sum of their results? 
+In practice we do this if we use the result of the first function to make a decision on whether we need 
 to invoke the second one or to decide on how to invoke it.
 
 We use a normal sequential invocation, because the code in the coroutine, just like in the regular 
@@ -110,12 +110,12 @@ Completed in 2017 ms
 
 ### Concurrent using async
 
-What if there are no dependencies between invocation of `doSomethingUsefulOne` and `doSomethingUsefulTwo` and
+What if there are no dependencies between invocations of `doSomethingUsefulOne` and `doSomethingUsefulTwo` and
 we want to get the answer faster, by doing both _concurrently_? This is where [async] comes to help. 
 
 Conceptually, [async] is just like [launch]. It starts a separate coroutine which is a light-weight thread 
 that works concurrently with all the other coroutines. The difference is that `launch` returns a [Job] and 
-does not carry any resulting value, while `async` returns a [Deferred] -- a light-weight non-blocking future
+does not carry any resulting value, while `async` returns a [Deferred] &mdash; a light-weight non-blocking future
 that represents a promise to provide a result later. You can use `.await()` on a deferred value to get its eventual result,
 but `Deferred` is also a `Job`, so you can cancel it if needed.
 
@@ -161,14 +161,14 @@ Completed in 1017 ms
 
 <!--- TEST ARBITRARY_TIME -->
 
-This is twice as fast, because we have concurrent execution of two coroutines. 
+This is twice as fast, because the two coroutines execute concurrently. 
 Note that concurrency with coroutines is always explicit.
 
 ### Lazily started async
 
-There is a laziness option to [async] using an optional `start` parameter with a value of [CoroutineStart.LAZY]. 
-It starts coroutine only when its result is needed by some 
-[await][Deferred.await] or if a [start][Job.start] function 
+Optionally, [async] can be made lazy by setting its `start` parameter to [CoroutineStart.LAZY]. 
+In this mode it only starts the coroutine when its result is required by 
+[await][Deferred.await], or if its `Job`'s [start][Job.start] function 
 is invoked. Run the following example:
 
 <div class="sample" markdown="1" theme="idea" data-min-compiler-version="1.3">
@@ -219,18 +219,18 @@ So, here the two coroutines are defined but not executed as in the previous exam
 the programmer on when exactly to start the execution by calling [start][Job.start]. We first 
 start `one`, then start `two`, and then await for the individual coroutines to finish. 
 
-Note that if we have called [await][Deferred.await] in `println` and omitted [start][Job.start] on individual 
-coroutines, then we would have got the sequential behaviour as [await][Deferred.await] starts the coroutine 
-execution and waits for the execution to finish, which is not the intended use-case for laziness. 
+Note that if we just call [await][Deferred.await] in `println` without first calling [start][Job.start] on individual 
+coroutines, this will lead to sequential behavior, since [await][Deferred.await] starts the coroutine 
+execution and waits for its finish, which is not the intended use-case for laziness. 
 The use-case for `async(start = CoroutineStart.LAZY)` is a replacement for the 
 standard `lazy` function in cases when computation of the value involves suspending functions.
 
 ### Async-style functions
 
 We can define async-style functions that invoke `doSomethingUsefulOne` and `doSomethingUsefulTwo`
-_asynchronously_ using [async] coroutine builder with an explicit [GlobalScope] reference.
-We name such functions with 
-"Async" suffix to highlight the fact that they only start asynchronous computation and one needs
+_asynchronously_ using the [async] coroutine builder with an explicit [GlobalScope] reference.
+We name such functions with the 
+"...Async" suffix to highlight the fact that they only start asynchronous computation and one needs
 to use the resulting deferred value to get the result.
 
 <div class="sample" markdown="1" theme="idea" data-highlight-only>
@@ -310,21 +310,21 @@ Completed in 1085 ms
 
 > This programming style with async functions is provided here only for illustration, because it is a popular style
 in other programming languages. Using this style with Kotlin coroutines is **strongly discouraged** for the
-reasons that are explained below.
+reasons explained below.
 
-Consider what happens if between `val one = somethingUsefulOneAsync()` line and `one.await()` expression there is some logic
+Consider what happens if between the `val one = somethingUsefulOneAsync()` line and `one.await()` expression there is some logic
 error in the code and the program throws an exception and the operation that was being performed by the program aborts. 
 Normally, a global error-handler could catch this exception, log and report the error for developers, but the program 
-could otherwise continue doing other operations. But here we have `somethingUsefulOneAsync` still running in background,
-despite the fact, that operation that had initiated it aborts. This problem does not happen with structured
+could otherwise continue doing other operations. But here we have `somethingUsefulOneAsync` still running in the background,
+even though the operation that initiated it was aborted. This problem does not happen with structured
 concurrency, as shown in the section below.
 
 ### Structured concurrency with async 
 
-Let us take [Concurrent using async](#concurrent-using-async) example and extract a function that 
+Let us take the [Concurrent using async](#concurrent-using-async) example and extract a function that 
 concurrently performs `doSomethingUsefulOne` and `doSomethingUsefulTwo` and returns the sum of their results.
-Because [async] coroutines builder is defined as extension on [CoroutineScope] we need to have it in the 
-scope and that is what [coroutineScope] function provides:
+Because the [async] coroutine builder is defined as an extension on [CoroutineScope], we need to have it in the 
+scope and that is what the [coroutineScope] function provides:
 
 <div class="sample" markdown="1" theme="idea" data-highlight-only>
 
@@ -338,8 +338,8 @@ suspend fun concurrentSum(): Int = coroutineScope {
 
 </div>
 
-This way, if something goes wrong inside the code of `concurrentSum` function and it throws an exception,
-all the coroutines that were launched in its scope are cancelled.
+This way, if something goes wrong inside the code of the `concurrentSum` function and it throws an exception,
+all the coroutines that were launched in its scope will be cancelled.
 
 <!--- CLEAR -->
 
@@ -379,7 +379,7 @@ suspend fun doSomethingUsefulTwo(): Int {
 
 > You can get full code [here](../kotlinx-coroutines-core/jvm/test/guide/example-compose-05.kt).
 
-We still have concurrent execution of both operations as evident from the output of the above main function: 
+We still have concurrent execution of both operations, as evident from the output of the above `main` function: 
 
 ```text
 The answer is 42
@@ -426,7 +426,8 @@ suspend fun failedConcurrentSum(): Int = coroutineScope {
 
 > You can get full code [here](../kotlinx-coroutines-core/jvm/test/guide/example-compose-06.kt).
 
-Note, how both first `async` and awaiting parent are cancelled on the one child failure:
+Note how both the first `async` and the awaiting parent are cancelled on failure of one of the children
+(namely, `two`):
 ```text
 Second child throws an exception
 First child was cancelled