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10.
float (*abc)(float (*def)(float *ghi));

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This one is really complicated. Adding in the parentheses only makes it seem worse:

float ((*abc)(float ((*def)(float *ghi))));

What is being declared? abc, def, or ghi?
Its not always easy to tell; a good rule of thumb is to go for the first name you meet, and see if it makes sense. So:

1. abc is being declared,
2. it is a pointer to something,
3. the something is a function. We can see that the function returns a float, but what is its parameter supposed to be? Analyse it separately. The parameter was declared float ((*def)(float *ghi)) which you might recognise from before:
   1. def is being declared,
   2. it is a pointer to something,
   3. the something is a function,
   4. the function takes a float * parameter,
   5. and returns a float

So, the whole thing, abc, being declared is just a simple variable. It can store a pointer to a function. But the function that it can point to is one that takes other functions as its parameter, and returns a float as its result.

I suppose we could describe the type of abc like this:

ABC is:
• A pointer to
  • a function
  • whose parameter is
    • a function whose parameter is
    • a pointer to a float
    • and whose result is a float
  • and whose result is a float

Don't worry, nothing this complex will appear on the test.

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