Question

int num_to_id(int num) {

static const int table[] = { 10, 15, 30, 50 }:

assert(std::find(&table[0], &table[4], num) != &table[4]);

return std::find(&table[0], &table[4], num) - &table[0]:

}

Can you explain how the lines 3 and 4 work exactly?

Answer 1

`Hey,

Note: If you have any queries related to the answer please do comment. I would be very happy to resolve all your queries.

Basically find function has syntax

result=find(first,last,val)

where

first, last

Input iterators to the initial and final positions in a sequence. The range searched is [first,last), which contains all the elements between first and last, including the element pointed by first but not the element pointed by last.

val

Value to search for in the range.
T shall be a type supporting comparisons with the elements pointed by InputIterator using operator== (with the elements as left-hand side operands, and val as right-hand side).

result is basically An iterator to the first element in the range that compares equal to val.
If no elements match, the function returns last.

SO, FOR LINE 3

assert(std::find(&table[0], &table[4], num) != &table[4]);

It searches in array table the value num and checks if address returned is not last then assert is true

LINE 4 IS BASICALLY THE RETURNED index from starting value where the value num is found

Kindly revert for any queries

Thanks.