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Rewrote some explanations #325

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35 changes: 23 additions & 12 deletions basics/loops.md
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Expand Up @@ -4,8 +4,9 @@ D provides four loop constructs.

### 1) `while`

`while` loops execute the given code block
while a certain condition is met:
`while` loops execute the given code block while a certain condition is `true`.
(If the condition starts out `false` the code block isn't executed at all,
and the flow of control continues from the statement following the loop's block.)

while (condition)
{
Expand All @@ -14,10 +15,10 @@ while a certain condition is met:

### 2) `do ... while`

The `do .. while` loops execute the given code block
while a certain condition is met, but in contrast to `while`
the _loop block_ is executed before the loop condition is
evaluated for the first time.
A `do .. while` loop unconditionally executes the given code block once,
and _then_ checks the condition.
So long as the condition is `true`, the code block is executed again, and the process
(check the condition, execute the code if the condition is `true`) is repeated.

do
{
Expand All @@ -27,7 +28,7 @@ evaluated for the first time.
### 3) Classical `for` loop

The classical `for` loop known from C/C++ or Java
with _initializer_, _loop condition_ and _loop statement_:
with _initializer_; _loop condition_; _loop statement_:

for (int i = 0; i < arr.length; i++)
{
Expand All @@ -38,24 +39,34 @@ with _initializer_, _loop condition_ and _loop statement_:
The [`foreach` loop](basics/foreach) which will be introduced in more detail
in the next section:

foreach (el; arr)
foreach (element; arr)
{
...
}

#### Special keywords and labels

The special keyword `break` will immediately abort the current loop.
In a nested loop a _label_ can be used to break out of any outer loop:
If a `break` statement is encountered, the flow of control will immediately
jump to the statement following the loop's block.
If a _labelled_ `break` statement is encountered, the flow of control will
jump to the statement following the labelled loop's block. This allows us
to immediately break out of two or more nested loops if required.

outer: for (int i = 0; i < 10; ++i)
{
for (int j = 0; j < 5; ++j)
{
...
break outer;
break outer; // control jumps to (A)
...
}
}
// (A) execution resumes here

A `continue` statement immediately moves the flow of control to the start of the loop's
next iteration e.g., to the top of a `while` loop to reevaluate the condition, to the top of a
`foreach` loop to get the next item,or to the _loop statement_ in a classic `for` loop.

The keyword `continue` starts with the next loop iteration.

### In-depth

Expand Down