שאלות ותשובות - Homeworks - Assignment 4 Frequently Asked Questions - Homeworks - Assignment 4 Вопросы и Ответы - Homeworks - Assignment 4 أسئلة وأجوبة - Homeworks - Assignment 4

		.. (לתיקייה המכילה)

Can we use our implementation of a linked list from Homework 2 ?

You should definitely not, for the simple reason it is written in C, not C++. (even though it might compile as C++, it's still not using C++'s new concepts)

BigInt and Map: what Standard Library classes can we use?

None. In particular, you may not use std::string, std::list, std::vector and so on. An exception to this is ostream.

Hint for Question 1 in the dry part:

Solving this question requires a small piece of knowledge from Tutorial 12: Regardless of whether a class is a template or not, you can define templated methods in it: class C { public: template <typename T> void f(const T& t); }; Here, we define the method C::f<T>(const T& t).

Can a BigInt be constructed from a string with leading zeros ("000001") ?

Yes, in which case the leading zeros should be ignored.

When iterating over a Map, what order should the items be accessed? In particular, to what item should map.begin() return an iterator ?

There is no requirement on the order. You can return the items in whichever order you wish, so long as all items are accessed exactly once.

Errata: In the wet part, in Map, you should assume the type V (Value) has a default constructor, as well as an assignment operator (operator=).

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Can we assume the number of digits of our BigInt can be represented as int ?

Yes.

Should we allow for the following code to compile ? Iterator<int, char> i;

You can assume an iterator will only be created through begin/end.

In 3.2.1, the "find" operation is said to return a value, while according to the example file it returns an iterator. Which is the correct one ?

In code, find() should return an iterator.

Question 2.2 - when doing cdgb << 3.0 I get 3, not 3.0. Is it ok ?

Yes - your output should be the same as if it was passed to cout.

Can we use strlen and strcmp in BigInt ?

Yes. Anything which is not an STL class.

Can we perform multiplications in BigInt not using long-multiplication ?

As we said in the exercise, you should use long-multiplication. Using something simpler might lead to an algorithm whose running time is proportional to the size of the number. This means that computing a 30-digit number on a modern computer will take about 10^20 seconds, which is around a 1000 times more than the age of the universe. The auto-checker might give up...

Map: can we assume KeyType has a default ctor ?

No. Please make sure your code compiles with such type.

Shake: one of the nouns is "summer's day". What should we do with it?

You can ignore this expression, it will not be used.

Question 2.2 (DebugStream) - the macro says debugStream, is it a typo ?

Yes. It should be DebugStream in the macro.

Shake: if a result is negative, what should be the state of the stack?

Untouched. That is, if the command is Romeo : Angel Angel Beautiful Without you should print that the result is negative, and the stack should still contain two numbers : Romeo : speak 2 Romeo : speak 1

What is ostringstream? How can we use it?

You should look for references for this class on the internet. One such resource is http://www.cplusplus.com/reference/iostream/ostringstream/

Shake: Where should we print errors to? cerr?

You should send all of the output/errors of Shake to the same place.

Shake: Is the following command legal? "<variable name> : bla bla bla bla bla sjhaklehja dajsldjaklsjd sadkjakld speak" ?

You can assume that if "speak" is not the third word in a line, it will not appear at all.

Shake: can "speak" appear more than once in one line ?

No, you can assume it will appear at most once.

BigInt: BigInt(12) and BigInt(012) return different numbers; is it ok ?

Yes; 012, in C/C++, is treated as an octal number, and actually equals 10 in decimal. You can ignore it, and in fact, you can't do anything about it - because in the code itself, you have no way to know if the number was prefixed with 0 or not.

BigInt: what should we do with BigInt(-43) ?

You may assume we will not initialize a BigInt with a negative number.

Is there a way to know the size of a C-style array ?

sizeof(name of array)/sizeof(type of elements in array) Note that this only works for arrays, not arrays which were converted to pointers (such as what happens when you pass an array to a function)

Map: should we define an operator[] for const maps ?

No, you don't have to.

BigInt: What should the following do, BigInt b("+1") ? Same question for BigInt b("").

Throw an exception, in both cases.

Shake: if an error occurs (.e.g, a result is negative) should we keep on executing commands from the rest of the line ?

Yes. So, if the program is Romeo : Angel Angel Beautiful without and Romeo : speak You should print an error, and then 3.