Confused about the lamda expression

[gnewsgroup]

I want to get my hands dirty with Linq, so I watched a few videos from
www.asp.net, and then turned to

http://msdn2.microsoft.com/en-us/library/bb397687.aspx

for some introduction about the new lamda feature of C#.

In the article linked above, there is an example reproduced here:

int[] numbers = {5,4,1,3,9,8,6,7,2,0 };
int oddNumbers = numbers.Count(n =n % 2 == 1);

I gave it a test, and oddNumbers has a value of 5.

I am confused by the 2nd line, i.e.,

int oddNumbers = numbers.Count(n =n % 2 == 1);

The Count method, as the MSDN doc says, returns the number of elements
in a sequence. So, does

n =n % 2 == 1

return a sequence? How does this happen?

Please shed some light. Thank you.

[Marc Gravell]

For info, the relevant MSDN page:

http://msdn2.microsoft.com/en-us/library/bb535181.aspx

[Michael A. Covington]

"gnewsgroup" <gn********@gmail.comwrote in message
news:5d**********************************@e60g2000 hsh.googlegroups.com...

>I want to get my hands dirty with Linq, so I watched a few videos from
www.asp.net, and then turned to

http://msdn2.microsoft.com/en-us/library/bb397687.aspx

for some introduction about the new lamda feature of C#.

In the article linked above, there is an example reproduced here:

int[] numbers = {5,4,1,3,9,8,6,7,2,0 };
int oddNumbers = numbers.Count(n =n % 2 == 1);

I gave it a test, and oddNumbers has a value of 5.

I am confused by the 2nd line, i.e.,

int oddNumbers = numbers.Count(n =n % 2 == 1);

The Count method, as the MSDN doc says, returns the number of elements
in a sequence. So, does

n =n % 2 == 1

return a sequence? How does this happen?

Please shed some light. Thank you.

[Michael A. Covington]

int[] numbers = {5,4,1,3,9,8,6,7,2,0 };

int oddNumbers = numbers.Count(n =n % 2 == 1);

I gave it a test, and oddNumbers has a value of 5.

I am confused by the 2nd line, i.e.,

int oddNumbers = numbers.Count(n =n % 2 == 1);

The Count method, as the MSDN doc says, returns the number of elements
in a sequence. So, does

n =n % 2 == 1

return a sequence? How does this happen?

No, it returns true or false depending on whether the number is odd.

A lambda expression is a way of creating a function without giving it a
name. Suppose you defined:

bool blah(n) { return n%2 == 1; }

That's a function named blah.

(n =n%2 == 1)

is the same function without a name.

The Count method takes a function that tells it which elements to count.
I'm not sure if

numbers.Count(blah)

is valid syntax, but it ought to be; it means "count the ones that return
'true' when given as the argument of 'blah'".

numbers.Count(n =n%2 == 1)

is the same thing without defining it separately giving it a name.

Lambda expressions are the stuff of which Lisp is made. They are a basic
tool of advanced, abstract computer programming.