Do while loop in r code#

The highlighted yellow below is the use of the do-while loop in the program. With this repetition, customers can order various types of drinks and desserts, all in one receipt.

Do while loop in r code#

If I had to make a guess, this snippet of code may have been adapted from one which did just that - and instead of simply removing the test, the author changed the & to ||. Furthermore, the do-while loop is also used in this program for drink and dessert orders. It will cause the while loop to halt at the first empty line.

Using & (AND) means that the whole statement will only return a zero status if read is able to read a line, AND that line is not empty. Something that is occasionally useful is to do while read -r line & ]. Note that such a file is not a valid text file, as that line is not a valid line) Viewed 22k times 1 I have a Program in R where i'm using do while loop. (As pointed out, this will catch the odd final line of input that is missing its trailing newline. Ask Question Asked 11 years, 2 months ago. endlist contains the end conditions and the values returned at the end of the loop. The 'change' portion is evaluated at the end of the loop. As far as I can see, || ] doesn't actually accomplish anything. The form for do looks like this: (do (varlist) (endlist) &body) varlist is composed of the variables defined in the loop, their initial values, and how they change after each iteration. Since the test returns true if $line is not empty, we're back to a nonzero exit, throwing us out of the while loop. return: Exit a function (returns result). It's a bit confusing as to why that would be there, but straightforward to explain what it does: || is an OR statement, and ] is only going to execute when read returns a nonzero exit code, at which point $line will be empty. while: Loop while a condition is TRUE: repeat: Infinite loop (until break stops execution). The second command runs if the first returns a falsy status, and the result is the exit status of the last command that executed.Д¬ompare: $ printf 'foo bar' | ( while read line do echo 'in loop: $line' done ДЄnd $ printf 'foo bar' | ( while read line || ] do The cmd1 ||В cmd2 construct is of course just like the equivalent in C. What's the point in adding a new line to the end of a file? and Why should text files end with a newline? on SO. wc -l counts the newline characters, and so ignores a final incomplete line. Other tools than read can also care, e.g. I said 'incomplete line', since the POSIX definitions of a text file and a line require a newline at the end of each line. Without the extra test, such an incomplete line would be read into $line, but ignored by the loop. If the input contains a line fragment without a newline in the end, this test will catch that, and the loop will process that final incomplete line, too. It's useful since read returns a success if and only if it sees a newline character before the end-of-file. Therefore, we need to specify five in header part.] tests if $line (the variable just read by read) is not empty. In our example, we write вЂњWelcome to Universe of Data ScienceвЂќ text five times. The total number of iteration is specified in header part. Second, a body containing a code block executed once for each iteration. First, a header specifies the number of iteration.

Logical condition needs to specified at the end of code block with if-break couple.ДЇlowchart of Loops in R вЂ“ for, while, repeatД¬heck Out: 6 Ways of Subsetting Data in R for-Loop in RДЄ for-loop includes two parts. repeat-Loop: Loop is infinite, but it needs logical condition to stop iteration.In this article, you will learn to create a while loop in R programming. while-Loop: Loop is infinite, but it needs logical condition in while-loop to stop iteration. Loops are used in programming to repeat a specific block of code.> do statement while (expression) This can be useful to write more readable code, although admittedly it gets used far less often then for and while loops and the potential of mixing it up with a while loop when skimming throu. The total number of iteration needs to be specified in for-loop. Answer: A do-while loop is executed at least once. In this guide, we will work on three loops in R вЂ“ for, while, repeat. This comprehensive guide includes the types of loops in R вЂ“ for, while, repeat. LoopsВ are the most powerful tools of theВ R programming language.