Floating point evaluation order in C -


I am using Code :: Blocks 10.05 on Windows 7.

I have compiled the following program,

contains #lt; Stdio.h & gt; Int main () {float f = 1.5; Printf ("% f \ n", (f1) * 1/2); Return 0; }

The output was 0.250000 . I understand this as follows,

Since f is a float (f-1) 0.500000 and full expression floating Point has been upgraded to arithmetic and therefore it is also considered as float to get 1/2 to 0.500000 and hence the result.

In addition to the following statement, 

  float F = 1.5; Printf ("% f \ n", 1/2 * (f -1));

gave the answer as 0.000000 expression here 1/2 divided the integer here (f-1) was evaluated for the first and full expression upgrade to floating point arithmetic.

Here again I thought that since the Polish notation, 

  * / 1 2 - f1

the first operation of the division And therefore the result is. Am I right about this assumption?

Finally, the following statement rejects all arguments; 

  float f = 1.5; Printf ("% f \ n", (f1) * (1/2));

The output is 0.000000 , but there is a Polish signage here, 

  * - f 1/2 2  < / Pre> 
 then  (f-1)  should be evaluated first and therefore the whole expression upgrade for the floating point arithmetic and the output should be  0.250000 . 
 
 Where have I gone wrong? Does this operator have to do something with the order of evaluation? What is the expression in C? Since

Since F is a float (F1) return float value of 0.500000 and the complete expression Has been upgraded to floating point arithmetic

No, where did you get that wrong information? The promotion for floating point only applies to one operator, one of which is an floating-point number operator. 1/2 is considered as a temporary point expression - like, it has not been evaluated. Since multiplication and division have the same priority and left-assessed as Associate, 

  (f - 1) * 1/2

Goes 

  (<-> 1) / 2)

and there 1 to float (At least), and then because ((1 - 1) * 1) also runs, then the second operator of the partition is 2 even float (or a high precision FP number, which is based on the compiler wants) has also been promoted.

Here I expect that (F1) will be evaluated first, the full expression has to be upgraded to floating point arithmetic.

No, this is a wrong hope, as I explained. This is a complete expression that is under conversion at floating-point not . This is another immediate operation of the only operator, one operand is a float in the expression: 

  (f - 1) * (1/2)

f - 1 a name . 1/2 is an integer, it is zero, and then the integer zero is promoted to float because the other operand of * Code> Name . The scope of / , however, is integers, so the division is evaluated according to the rules of integer arithmetic.


-

Comments

Post a Comment

Popular posts from this blog

sqlite3 - UPDATE a table from the SELECT of another one -

I have the first table article where some data is missing. In the table, articles_tmp I have a part of the missing data. So I want to update the articles. Where the path path is data in articles_tmp.path where the path is not zero . With SQLite , it does not work: update article SET path = (SELECT at.path FROM Articles_tmp as AS, WHERE at.article_id = a.id and a.asp, the text is in the form and not on. It has been transmitted) where the path is null MS Access Along with, it works fine: Update Articles Join the Inner Articles at articles_tmp articles.id = articles_tmp.id SETP articles.path = articles_tmp.path Can anyone help? Sin CE SQL Server Syntax, which I provided, was not working, here this solution With whom I have come. A little modification of your original query, but with my "correlation" suggestion added. There is a SQL Bella for this: Here is the code: update article SET path = (SELECT path from articles_tmp AS T WHERE t.id
Read more

c# - Showing a SelectedItem's Property -

So I have enabled a rightclick option for my DataGrid. I want to display the only chosen property but it is not behaving like what I would like it to display my name and additional. Public category Paymentinfo {public int PaymentNo {get; Set; } Public string date {get; Set; } Public Double Pay {get; Set; } Public Double Principle {get; Set; } Public Double Interest {get; Set; } Public Double Balance {Received; Set; }} Private Zero MenuItem_OnClick (Object Sender, RoutedEventArgs e) {MessageBox.Show (AmortGrid.SelectedItem.ToString ()); } I'm trying to apply it without using a View Module! If I place a breakpoint where the messagebox and the recipient place it on selected ITEM, then this property will display the payment. A date-payment-principle-interest-balance is the only value that needs payment. Was hoping that it would be something like this MessageBox.Show (AmortGrid.SelectedItem.PaymentNo.ToString ()); When you call ToString () So you get the class typ
Read more

javascript - Render HTML after each iteration in loop -

I'm trying to gradually increase the font size of text on a web page. The code works in my place, although the new HTML / CSS does not render after every iteration of the loop and when all this is done, then display only the text of 100 px size. To see the text as if it is slowly zooming, I need to do this JavaScript is down because it is being used from a different file here is what I have ... < Pre> & lt; P class = "game-title" style = "font-size: 50px" & gt; Test & lt; / P & gt; Function sleep (milliseconds) {var start = new date (). GetTime (); For (var i = 0; i & lt; 1e7; i ++) {if ((new date). GetTime () - start) & gt; Milliseconds {break; CSS ('font-size', 'parseInt ($ (' game-title '). CSS (' font-size ')) + 1 + "pixels"); } While (parasont ($ ('# text'). Css ('font-size')) & lt; = 100) {sleep (1000); IncreaseSize (); Using CSS: Use of jQuery (sample):
Read more