Questions about conditionals without a comparison

Question

What does these conditions mean in C++:

if (whereto)
if (!nE)
for (cur=first; cur; cur=cur->next)
if (del->prev)

I am still beginner in C++. learned the basic conditions but those conditions are not clear for me. What do the expressions whereto, !ne, cur, and del->prov mean in a conditional

Could someone give me a hint?

https://stackoverflow.com/questions/388242/the-definitive-c-book-guide-and-list — Oliver Charlesworth, Jul 14 '17 at 20:57
@Ron sorry man tried to write bold some people now what is the question. — Nano, Jul 14 '17 at 20:58
What are the types of the variables in these expressions? Why are you confused? — jaggedSpire, Jul 14 '17 at 21:00
@jaggedSpire the problem is I usually write for example if(whereto =0) .. but now I don't see the condition of the if or if(!=ne). — Nano, Jul 14 '17 at 21:02
***for example if(whereto =0)*** you mean `if(whereto == 0)` — drescherjm, Jul 14 '17 at 21:12

dbush · Accepted Answer · 2017-07-14T21:54:15.540

6

Those expressions are being evaluated in a boolean context.

Here, a value of 0 (or NULL) is false, while any non-zero (or non-null) value is true.

So the above is equivalent to:

if (whereto != 0)
if (nE == 0)
for (cur=first; cur != NULL; cur=cur->next)
if (del->prev != NULL)

edited Jul 14 '17 at 21:54

answered Jul 14 '17 at 20:59

dbush

205,898
23
218
273

so by writing if(whereto) , we mean if(whereto==null)? – Nano Jul 14 '17 at 21:04
***so by writing if(whereto) , we mean if(whereto==null)?*** It means `if(whereto != nullptr)` or `if(whereto != 0)` – drescherjm Jul 14 '17 at 21:13
@drescherjm thanks man. Now I got it. thanks everyone. – Nano Jul 14 '17 at 21:27
@Kashan Glad I could help. Feel free to [accept this answer](https://stackoverflow.com/help/accepted-answer) if you found it useful. – dbush Jul 14 '17 at 21:54

Questions about conditionals without a comparison

1 Answers1