Question

Today at work we came across the following code (some of you might recognize it):

#define GET_VAL( val, type ) \     {                                                   \         ASSERT( ( pIP + sizeof(type) ) <= pMethodEnd ); \         val = ( *((type *&)(pIP))++ );                  \     } 

Basically we have a byte array and a pointer. The macro returns a reference to a variable of type and advance the pointer to the end of that variable.

It reminded me of the several times that I needed to ‘think like a parser’ in order to understand C++ code.

Do you know of other code examples that caused you to stop and read it several times till you managed to grasp what it was suppose to do?

Answer 1

The inverse square root implementation in Quake 3:

float InvSqrt (float x){     float xhalf = 0.5f*x;     int i = *(int*)&x;     i = 0x5f3759df - (i>>1);     x = *(float*)&i;     x = x*(1.5f - xhalf*x*x);     return x; } 

Update: How this works (thanks ryan_s)