C language collection (2): Symbol Overloading

A very important feature of C language is conciseness. But sometimes it is too concise. Simply add, modify, or delete a character, the original program can be completely different.

A concise C language allows a symbol to indicate different meanings in different contexts. This is called the symbol "overload ".

For exampleVoidSymbol, which has the following common meanings:

1> as the return type of the function, it indicates that no value is returned.

2> in Pointer declaration, it indicates a universal pointer

3> In the parameter list of the function, it indicates that no parameter exists.

Here is a multiplication number.*For more information, see the "bad" symbol overload.

Code:

1 # include <stdio. h> 2 3 int main () 4 {5 int p, N = 5, * q = & N; 6 7 p = N * sizeof * q; 8 printf ("p = % d. \ n ", p); 9 10 p = N * sizeof (int) * p; 11 printf (" p = % d. \ n ", p); 12 13 p = N * sizeof (int) * q); 14 printf (" p = % d. \ n ", p); 15 16/* error: binary operator * operand ('unsigned int' and 'int *') invalid */17 // p = N * sizeof (int) * q; 18 // printf ("p = % d. \ n ", p); 19 20 return 0; 21}

Do not look at the definition of the variable first (because the type of the variable will prompt the function), directly look at the line7, 10, 13, 17 expressions, do you know what they mean?

Okay. Let's see the results,

Randy @ ubuntu :~ /C_Language $./a. out
P = 20.
P = 400.
P = 20.

Explanation:

Line7: we have encountered sizeof again. Remember, sizeof is an operator, not a function. When sizeof is of type, it must be called parentheses, such as sizeof (int ). N = 5, q is the pointer, pointing to the N address,

So * q = 5, is int type, sizeof (int) = 4, so p = 5*4 = 20.

Line10: p = 5*4*20 = 400.

Line13: It's actually the same as line7.

Line17: this expression has been injected because it fails to be compiled. Should I know why? (The answer is annotated)

 

Summary: In this example, if a small * is not a little human bypass, there are also many other symbol overload examples.

For exampleStatic, extern, &, <,().

Is this the beauty of the C language concise? Discussion!

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