The University of Iowa
The College of Liberal Arts and Sciences
Department of Computer Science
Programming Languages and Tools:
CS:3210:0001
Lecture/Lab #3
Programming with C++
Declaration vs definition, function declaration, variables and types
Warm-up
import os
print( "Current directory:",
os.getcwd() )#include <iostream>
#include <filesystem>
int main() {
std::cout
<< "Current directory: "
<< std::filesystem::current_path()
<< "\n";
}Python
C++
Can we do this in C++?
int main() {
print( "Current directory:", getcwd() );
}Exercise 1
Provide definitions of functions `print` and `getcwd` to make the program compile and produce the expected output
-
Open the exercise template
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Write your code, press Run to test
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When you're done, grab your Repl's link and send it as a direct message to me (agurtovoy)
-
Click on the corresponding option in the "Lab3 exercises" poll in #general
Instructions
Declaration vs definition
void hello( std::string name );
int main() {
hello( "Bob" );
}
-
A declaration makes a name known to the compiler and associates it with a type.
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A definition creates/provides an implementation of the associated entity.
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C++ allows multiple declarations of the same entity as long as declarations are identical.
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Only one entity definition is allowed.
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A declaration allows us to use the entity, but we need to provide the definition eventually to be able to compile the program into an executable.
Function declaration
void hello( std::string );
void hello( std::string name );
void hello( std::string fist_name );
void hello( std::string ignored ) {}
int main() {
hello( "Bob" );
}
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Function parameter names are optional
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Function parameter names can vary between declarations
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Function parameter names can vary between a declaration and the definition
Exercise 2
Fix the program's compilation errors without changing the order of function definitions
-
Open the exercise template
-
Write your code, press Run to test
-
When you're done, grab your Repl's link and send it as a direct message to me (agurtovoy)
-
Click on the corresponding option in the "Lab3 exercises" poll in #general
Instructions
Variables and types
#include <iostream>
int main()
{
int n = 42;
float pi = 3.14;
bool b = pi < 5;
char c = 'A';
std::cout
<< "n: " << n << "\n"
<< "pi: " << pi << "\n"
<< "b: " << b << "\n"
<< "c: " << c << "\n"
;
}
- Every program entity has a type that determines the operations that may be performed on it
- For variables, type also determines their size, memory layout, and the range of supported values
Programming with C++, Spring 2020, Lecture #3
By Aleksey Gurtovoy
Programming with C++, Spring 2020, Lecture #3
Declaration vs definition, function declaration, variables and types
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