Possibly need is “all the elements in the list”. For example, if you’re traversingĪ list of elements, you know that the maximum number of loop iterations you can
Times that you’ll need to execute the body. Use a for loop if you know, before you start looping, the maximum number of So why have two kinds of loop if for looks easier? This next example showsĪ case where we need the extra power that we get from the while loop. Test for completion, and then make sure you change something in the body so Loop one has to control the loop variable yourself: give it an initial value, The programmer - than the equivalent for loop. What you will notice here is that the while loop is more work for you. In other cases, it is not so easy to tell. Increments each time through the loop, so eventually it will have to equal The value of len(name) is finite, and we can see that the value of pos In the case here, we can prove that the loop terminates because we know that The directions on shampoo, lather, rinse, repeat, are an infinite loop. Loop will repeat forever, which is called an infinite loop.Īn endless source of amusement for computer programmers is the observation that The body of the loop should change the value of one or more variables so thatĮventually the condition becomes false and the loop terminates. The body consists of all of the statements below the header with the same If the condition is true, execute each of the STATEMENTS in the body and If the condition is false, exit the while statement and continue
The flow of execution for a while statement works like this:Įvaluate the condition ( BOOLEAN EXPRESSION), yielding False or The name was", name + "." ) else : print ( " \n Great, you got it in", pos + 1, "guesses!" ) ", end = '' ) guess = input ( "Guess again: " ) pos = pos + 1 if pos = len ( name ) and name != guess : print ( "Too bad, you couldn't get it. Try to guess it: " ) pos = 0 while guess != name and pos < len ( name ): print ( "Nope, that's not it! Hint: letter ", end = '' ) print ( pos + 1, "is", name + ". Name = 'Harrison' guess = input ( "So I'm thinking of person's name. The following program outputs a sequence of values in the left columnĪnd 2 raised to the power of that value in the right column:
In the table the Intel Pentium processor chip used to perform floating-pointĪlthough a log table is not as useful as it once was, it still makes a goodĮxample. In some cases, there have been errors in the underlying tables, most famously For some operations, computers use tables of values to get anĪpproximate answer and then perform computations to improve the approximation.
Soon thereafter,Ĭomputers and calculators were so pervasive that the tables became obsolete. Is great! We can use the computers to generate the tables, so there will be noĮrrors.” That turned out to be true (mostly) but shortsighted. When computers appeared on the scene, one of the initial reactions was, “This
#Syntax for for loop in r full#
The tables was slow and boring, and they tended to be full of errors. To make that easier, mathematicsīooks contained long tables listing the values of these functions. Were readily available, people had to calculate logarithms, sines and cosines,Īnd other mathematical functions by hand. One of the things loops are good for is generating tables.
0 kommentar(er)
