Strings are sequential collections of zero or more characters such as letters, numbers and other symbols. There are actually two types of strings in C++ . The C++ string or just string from the <string> library is the more modern type, and it is very similar to the Python string class. The old style C-string which is essentially an array of char type. The char type itself is actually distinct from both types of strings.
char cppchar = 'a'; // char values use single quotes
string cppstring = "Hello World!"; // C++ strings use double quotes
char cstring[] = {"Hello World!"}; // C-string or char array uses double quotes
In older versions of C++, you must use a char array to work with filenames. In modern C++ (from C++11 onward), however, you can use a C++ string for everything. Since C++ strings are so much nicer and similar to Python strings, I would not recommend using C-strings.
::: {.mchoice answer_a=”An array of characters that ends with a terminating null character. i.e. \0” answer_b=”A sequential data structure consisting of zero or more characters” answer_c=”A data structure consisting of an ordered collection of data elements of identical type in which each element can be identified by an array index.” answer_d=”sequence container storing data of a single type that is stored in a dynamically allocated array which can change in size.” correct=”a” feedback_a=”Correct! a c-string is different from a string” feedback_b=”Close, but that is the definition of a string, not a c-string” feedback_c=”Sorry, thats not a string or a c-string” feedback_d=”No, that’s a vector”} cstringquestion1_1
What is the correct definition of c-strings? :::
Because strings are sequences, all of the typical sequence operations work as you would expect. In addition, the string library offers a huge number of methods, some of the most useful of which are shown in Table 4<tab_stringmethods>{.interpreted-text role=”ref”}.
- ::: {#tab_stringmethods}
- +—————–+————————+————————+
- | Method Name | Use | Explanation |
- +=================+========================+========================+
- | >
[ ]| >astring[i]| > access value of | - | | | > character at index i |
- +—————–+————————+————————+
- | >
=| >astring[i]=value| > change value of | - | | | > character at index i |
- +—————–+————————+————————+
- | >
+| >string1 + astring2| > concatenate strings | - +—————–+————————+————————+
- | >
append| > `a | > Appends a string to | - | | string.append(string)` | > the end of the |
- | | | > string |
- +—————–+————————+————————+
- | >
push_back| > `as | > Appends a character | - | | tring.push_back(char)` | > to the end of the |
- | | | > string |
- +—————–+————————+————————+
- | >
pop_back| >astring.pop_back()| > Deletes the last | - | | | > character from the |
- | | | > end of the string |
- +—————–+————————+————————+
- | >
insert| > `astr | > Inserts a string at | - | | ing.insert(i, string)` | > a specific index |
- +—————–+————————+————————+
- | >
erase| > | > Erases an element | - | |
astring.erase(i, j)| > from one index to | - | | | > another |
- +—————–+————————+————————+
- | >
find| >astring.find(item)| > Returns the index of | - | | | > the first occurrence |
- | | | > of item |
- +—————–+————————+————————+
- | >
size| >astring.size()| > Returns the size of | - | | | > the string |
- +—————–+————————+————————+
-
Table 4: String Methods Provided in C++ :::
Matching
::: {.dragndrop feedback=”Feedback shows incorrect matches.” match_1=”[ ]|||Accesses value of an element.” match_2=”=||| Assigns value to an element.” match_3=”push_back|||Adjoins a character to the end of the string.” match_4=”pop_back|||Removes the last character from the end of the string.” match_5=”insert|||Injects a string at a specific index.” match_6=”erase|||Deletes an element from one index to another.” match_7=”size|||Returns the capacity of the string.” match_8=”+|||Connects strings.” match_9=”append|||Adjoins a string to the end of the string.” match_10=”find||| Returns the index of the first occurrence of item.”} matching_strings
Match the String operations with their corresponding explanation. :::
::: {.tabbed} intro_string
::: {.tab} C++
::: {.activecode caption=”Strings in C++” language=”cpp”} introstring_cpp
// This function concatenates the string hello World // Then it says where World begins in the concatenated string #include <iostream> #include <string> using namespace std;
int main(){
string mystring1 = "Hello"; string mystring2 = "World!"; string mystring3;
mystring3 = mystring1 + " " + mystring2; cout << mystring3 << endl;
cout << mystring2 << " begins at "; cout << mystring3.find(mystring2) << endl;
return 0;
} ::: :::
::: {.tab} Python
::: {.activecode caption=”Python strings”} introstring_py
"""This does the same thing as the C++ function """ def main(): mystring1 = "Hello" mystring2 = "World!"
mystring3 = mystring1 + " " + mystring2 print(mystring3)
print(mystring2, end=" ") print("begins at", end=" ") print(str(mystring3.find(mystring2)))
main() ::: ::: :::
Check your understanding by completing the following question.
::: {.dragndrop feedback=”Feedback shows incorrect matches.” match_1=”char|||’a’” match_2=”char array|||{‘a’}” match_3=”string|||"a"”} string_types
Drag each data type to its' corresponding C++ initialization syntax. :::