C++ Deck 9

Question 1

Which library of the Standard Template Library pertains to strings?

Answer 1

<string>
</string>

Question 2

How are strings declared in <string> compared to without it?</string>

Answer 2

They can be declared as regular variables instead of arrays.

Question 3

What are four functionalities supported by the <string> library?</string>

Answer 3

1. Use of the assignment operator (=)
2. Comparison operators (==, !=, etc.)
3. The + operator for concatenation
4. Type conversions from c-strings to string objects

Question 4

Is “string” a C++ keyword?

Answer 4

No, it’s an identifier taken from the <string> library.</string>

Question 5

When comparing strings using the <string> functions, what do the > and < operators do?</string>

Answer 5

They compare two strings and determine which one comes first lexicographically.

“apple”<”apply” Apple comes before apply
“apple”>”Apply” apple comes after Apply
“apple”>”Zebra” apple comes after Zebra

Question 6

What does <string> class member function:</string>

size()

do?

Answer 6

Returns the length of the string.

Question 7

What does <string> class member function:</string>

length()

do?

Answer 7

Returns the length of the string (same as size() function)

Question 8

What does <string> class member function:</string>

capacity()

do?

Answer 8

Returns the current allocated size of the string object. The capacity may be larger than current usage, which is the length()

Question 9

What does <string> class member function:</string>

resize(X, CH)

do?

Answer 9

Changes the string’s allocated size to X. If X is bigger than the currently stored string, the extra space at the end is filled in with the character in CH.

Question 10

What does <string> class member function:</string>

clear()

do?

Answer 10

Delete the contents of the string. Reset it to an empty string.

Question 11

What does <string> class member function:</string>

empty()

do?

Answer 11

Return true if the string is currently empty, false otherwise.

Question 12

What does <string> class member function:</string>

at(x)

do?

Answer 12

Return the character at position x in the string. Similar to using the [] operator.

e.g.
string.at(0)
is similar to
string[0]

in that they both reference the first character of the string.

Question 13

What does <string> class member function:</string>

substr(X,Y)

do?

Answer 13

Returns a copy of the substring (i.e. a portion of the original string) that starts at index X and is Y characters long.

Leaving the Y blank will just return the substring starting at index X and going all the way until the end.

Question 14

What does <string> class member function:</string>

append(str2)

do?

Answer 14

Appends str2 (a string or a c-string)

Appending adds something onto the end of an existing string rather than replacing what’s already there.

Question 15

What does <string> class member function:</string>

append(str2, Y)

do?

Answer 15

Appends the first Y characters from str2 (a string or character array)

Question 16

What does <string> class member function:</string>

append(str2, X, Y)

do?

Answer 16

Appends Y characters from str2, starting at index X

Question 17

What does <string> class member function:</string>

append(X, CH)

do?

Answer 17

Appends X copies of the character CH

Question 18

What does <string> class member function:</string>

str.find(str2, X)

do?

Answer 18

Returns the first position at or beyond position X where the string ‘str2’ is found inside of ‘str’

Question 19

What does <string> class member function:</string>

str.find(CH, X)

do?

Answer 19

Returns the first position at or beyond position X where the character CH is found in ‘str’

Question 20

What does <string> class member function:</string>

str.compare(str2)

do?

Answer 20

Performs a comparison, like the c-string function stcmp. A negative return means str1 comes first. Positive means str2 comes first. 0 means they are the same.

Question 21

What does <string> class member function:</string>

str.compare(str2, X, Y)

do?

Answer 21

Compares the portions of the strings that begin at index X and have length Y.

Question 22

What does <string> class member function:</string>

str.insert(X, Y, CH)

do?

Answer 22

Inserts the character CH into string str Y times, starting at position X.

Question 23

What does <string> class member function:</string>

str.insert(X, str2)

do?

Answer 23

inserts str2 (string object or char array) into str at position X

Question 24

C-strings pass by _____.

Answer 24

address

Question 25

C++ string objects pass by _____.

Answer 25

value

Question 26

True or False: C++ string class objects grow their capacity automatically when the number of characters exceeds the allocated space.

Answer 26

True.

By contrast, C-strings do NOT do this.

Question 27

What is the value returned by the find() function in the string class?

Answer 27

The index of the position of the first matched character (if the string were matched)

Question 28

Which C++ string class member function returns the internal c-string of the object?

Answer 28

c_str()

Question 29

True or False: The assignment (=) operator can be used to copy C++ string objects and C-strings.

Answer 29

False, it only works for C++ string objects

Question 30

Objects of a class use which operator to access its internal members?

Answer 30

The . operator

e.g.

string3.find()
^