float vs. inline-block changes margin and parent height - html

Question

So I have been trying to wrap my mind around this and cant figure it out why.
Note: Margin and padding is 0.
The 1st example is
<div> <!-- Gray Box -->
<div> <!-- Purple Box -->
</div>
</div>
I have two images - One is float, the other is inline-block.
The height of the div is shown by the gray color.
float: left;
display: inline-block;
The 2nd example is
<div>
<ul>
<a href = "#">
<li>
<img src = "...">
</li>
</a>
</ul>
</div>
Again, left and inline-block do different things
float: left;
display: inline-block;
Bottom Line
Any suggestions beside the question is welcome.
I don't know why margin / padding is changing and why div size matters by float and display. Thanks

Answer 1

There are 2 problems here.
1) Like someone mentioned in the comments, inline block takes space into account, meaning on the parent div you should have:
font-size:0;
2) Floating takes the element out of the document flow, meaning the parent will expand only past the last non floated child element. To fix this you should put a clearfix class in your css and add it to the parent of the floated element(s).
.clearfix::after{
content:'';
display:block;
clear:both;
}
So once you've done this your first example should look like this:
<div class="clearfix"> <!-- Gray Box -->
<div style="float:left"> <!-- Purple Box -->
</div>
</div>
Now the gray box should expand past the purple box;
As a matter of consistency i don't think you should mix inline-block with floating. One, it won't work on the same element and 2, they are designed for different things.