C#•2d ago

Expression vs Statement vs Expression statement in programming

Hello guys, I know it's a silly question but what is the difference between a statement, an expression and an expression statement in programming? From what I understood (please confirm and add to it if required), an expression should always return a value, a statement may or may not return a value (what does this mean? can someone elaborate and give example pls). What about "expression statement"

14 Replies

spit on that Thang CHO BOC•2d ago

you mean this?

int x;        // Just a declaration, no error declaration statement.
x = 42;       // Assigning a value
Console.WriteLine(x); // Using x after it’s been assigned

int y;        // Just a declaration, no error.
y = 5 + 3;    // expression statement
Console.WriteLine(y); // Using x after it’s been assigned

//var y = return x; <-- Not valid in C#

int x;        // Just a declaration, no error declaration statement.
x = 42;       // Assigning a value
Console.WriteLine(x); // Using x after it’s been assigned

int y;        // Just a declaration, no error.
y = 5 + 3;    // expression statement
Console.WriteLine(y); // Using x after it’s been assigned

//var y = return x; <-- Not valid in C#

FakerOP•2d ago

the thing is am confused about how to differentiate a statement from an expression since a statement itself can return a value. if we have 5 + 3; this gives us 8, if we don't assign it to y, this is called an expression or statement

spit on that Thang CHO BOC•2d ago

5 + 3; standalone will not work in C# (safe to say C, C++)

FakerOP•2d ago

nah, I mean for example inside a console.writeline statement

Thinker•2d ago

A statement is something which does something, for instance Console.WriteLine writes to the console. An expression is something which returns a value, for instance x + 1 returns the value contained within x plus 1.

spit on that Thang CHO BOC•2d ago

void PrintResult(int result)
{
    Console.WriteLine($"Result: {result}");
}

PrintResult(5 + 3);

void PrintResult(int result)
{
    Console.WriteLine($"Result: {result}");
}

PrintResult(5 + 3);

you can do that just tested it to be sure key point - The expression must evaluate to a value of a type that is compatible with the function’s parameter. - The expression must not have syntax errors or invalid operations.

Sehra•2d ago

https://learn.microsoft.com/en-us/dotnet/csharp/programming-guide/statements-expressions-operators/statements

Statements - C#

Learn about statements in C# programming. See a list of statement types, and view code examples and additional resources.

FakerOP•2d ago

Yep I see the thing is, statements must do something, like we can't say x + 1 is a statement on its own because it doesn't do anything unless we assign it to some variable

Thinker•2d ago

yep x + 1; doesn't make sense because it doesn't "do anything" However, when you call a method, that might do something, but it may also return a value! That is why we can call methods both as statements and as expressions, eg. we can call a method like int x = DoSomething() + 1; but also as DoSomething();. When we specifically use a method call as a statement, that is called an expression statement.

FakerOP•2d ago

ah yeah I see yep, got it, thanks !!

Thinker•2d ago

np :meow_owo:

spit on that Thang CHO BOC•2d ago

x + 1; will return compile error x++; works but does nothing
very interesting

FakerOP•2d ago

x++ is like x = x + 1;

spit on that Thang CHO BOC•2d ago

okay it works like normal C :NotedHmm:

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Expression vs Statement vs Expression statement in programming

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