Use the range-based for statement to construct loops that must execute through a 'range', which is defined as anything that you can iterate through—for example, std::vector, or any other C Standard Library sequence whose range is defined by a begin and end. C for loop - A for loop is a repetition control structure that allows you to efficiently write a loop that needs to execute a specific number of times. It is the simplest loop of C. This loop executes one or more statements while the given condition remains true. It is useful where the number of iteration are not known in advance. Jul 08, 2013 I cannot figure out what to do. I know something is wrong with my formula and variables too maybe? A country club charges $2500 per year for membership and will increase its membership fee by 4% for the next six years. Write a program segment using a loop to display the projected rates for the next six years. I originally tried using a while loop but I thought for loop would work better.
When creating applications in C++, it's often extremely useful to be able to use the programming concept of a loop. This is a piece of code that repeats while a certain condition is true. In this tutorial, we will be learning how to use the two most basic kinds of loops -- the
while
loop and the for
loop.While
The while loop is the simplest of loops in C++ and pretty much does exactly what we defined in the basic introductory paragraph. It loops a piece of code while a certain condition is true. The loop is created using the
while
keyword, followed by a condition in brackets (you already know how to formulate these - they are exactly as found in if statements!), followed by the code you want to execute in curly brackets. Remember that we can also use a bool value as the condition if we want -- as in if statements, it's all about whether true
or false
is returned.So let's get some test code running. One of the simplest (and most common) examples in C++ is simply counting up numbers. If we create an integer variable and set it to 0, create a while loop that executes code while the number is less than or equal to 5, output the integer variable in the loop and then add one to the number during the loop - we should have a loop that goes round 5 times and counts up to 5 (think about it, the logic all makes sense). The code might be something like the following:
On running this code, you should see that it all works as planned! The program counts up from 1 to 5 and hence the loop and condition were formulated correctly. It's worth noting that adding one to the variable is called 'incrementing' it, and can be accomplished via many methods (
number = number + 1
, number += 1;
, and some other we'll cover in the future).Obviously loops aren't only useful for counting up numbers (although they are very good at that, as we've seen!) -- let's say we wanted to only move the program on after the user had entered a 'valid' number into the program for example. We could create a loop that only breaks after the input has been validated! Booleans (
bool
s) serve a perfect purpose for this, and so we could do something like this:It's worth noting that the code above could also work by using
while(true)
(an infinite loop) and then using break;
to break out of the loop if the input is valid.Increment and Decrement operators
In order to progress onto 'for' loops, we're just going to learn a little bit about incrementing and decrementing using some operators built into the core language of C++.
Incrementing
Remember the while loop code we wrote earlier in this tutorial? We wrote
number = number + 1
to add one to the variable number
that we were using at the time, to step through the while loop a certain number of times. We glossed over the fact that this was called incrementing and that there are a variety of ways to do it. The first I've just covered, the second is using the +=
operator to do something like number += 1
, but there is also a third, even easier way to accomplish this. This way, unlike the others, can only be used to add one to a variable rather than adding a number of your choice. This method is using something called the increment operator. The increment operator is shown in C++ by writing ++
on either the left or right side of a variable - as you might expect, it increments that variable.So if we were to go back and re-factor our while loop code to make it use the increment operator instead of using the current, stretched out method - we would end up with something like this:
There we go, doesn't that look a bit better! What's great about this is that you can also use the variable while it's being incremented, for example in a simple
cout
! It's important to note that the operator does different things when put at different sides of a variable - this can be seen most noticeably when using the variable while incrementing as previously described. So firstly let's use the post-increment (the one with the ++
after the variable name), this should use the variable and then increment it. For example the following will output 10, then 11:In contrast to this, using the pre-increment (the one with the
++
before the variable name) will increment the variable before using it. So the following should output 11, then 11:A small difference, but incorrect usage in a program could completely screw up a system.
Decrementing
Decrementing is extremely similar to incrementing, however minuses one from the variable instead of adding one. The decrement operator, rather unsurprisingly, is
--
and just like the increment operator has pre and post versions (which act just like the increment ones). I'm not really going to go into much depth here, as it should be blindingly obvious how to use the decrement operator if you know how to use the increment operator correctly. Take the following pieces of code for example, try and guess what will output what:If you're stuck, try re-reading the incrementing section or just compiling the code to see the results. Just remember, the post operator always does the operation after usage, and the pre operator always does the operation before usage.
For
The 'for' loop is essentially just another kind of loop, much like
while
. It, however, makes creating a loop which should loop a certain number of times really simple.![C for loop C for loop](/uploads/1/2/5/7/125757286/633370461.jpg)
Perhaps one of the best ways to show off the 'for' loop is to simply cycle through and output all the elements in an array. So first, let's just create an array that we can cycle through inside of our
main
function - I'm going to use an array of string
s (make sure to #include <string>
!):Now we have the array, let's start creating the loop itself. The 'for' loop is created by using the
for
keyword, and then specifying three different sections, separated by semicolons, inside brackets. Code to execute each loop is then put inside curly brackets that follow this. The first section that the loop takes is called the declaration, and should contain the declaration (and probably initialization) of an iterator variable that the loop will use - just like the int number;
variable we used with some 'while' loops. The second section is called the condition - this should contain the condition which must remain true for the loop to keep going. The third and final section, is called the update - this should contain some code which updates the iterator variable (for example, incrementation). The general idea should look something like the following:All we have to do now is populate the sections. Something like the following will do fine to loop round 10 times (with
i
going from 0 to 9):The real power of the 'for' loop then comes from using 'i' inside the loop. 'i' should get incremented each time, and so 'i' will contain the values 0-9 in different stages of the loop - we could use this to simply count up, or to do other more interesting tasks. It's worth noting while we're talking about the sections of these loops, that not all sections are necessary. If you wanted an infinite loop that uses
for
for example, you could leave all the sections empty and simply write:Once again,
break;
could be used to break out of the loop at any point inside of it. Getting back to our purpose of looping through an array though, we want to execute the code inside as many times as our array has elements. We could hard-wire it in and have it loop round exactly five times and access element 'i' each stage of the loop, but this isn't the most elegant solution as we may wish to change the number of elements in the array at a later date, at which point we would have to update all the code (which isn't what we want). A better solution might be to get the exact number of elements in the array, but unfortunately there isn't a nice function or anything to do that -- we can however count the number of elements if we get a bit creative.C For Loop Syntax Value
There are a number of ways to go about doing this, but by far the easiest way to do it in our case is to divide the total size of our array (in bytes) by the space each element takes up (in bytes). There is a function that can get the size of stuff (in bytes), and that function is called
sizeof
. With all of this in mind, the calculation to get the number of elements should look like the following:![Dev c for loop counter for sale Dev c for loop counter for sale](/uploads/1/2/5/7/125757286/805366615.jpg)
Note that although we are dividing by the
sizeof
the first element in the array above, the result would be the same if we divided by sizeof(string)
-- using the first element in the array is just slightly more flexible as we may wish to change the array datatype in the future (although hopefully not to anything too complex as this method of counting the elements doesn't work with everything).So now we can count the elements in the array, writing out the for loop shouldn't be too difficult. We want to create an iterator variable, which we'll call i
, loop while it is less that the number of elements (the calculation we just worked out), and then increment i
each time. The result should look something like the following:From here, all we need to do is add the
-->cout
that outputs the array element with the index of i
, i.e. all of the array elements from index 0 to index 9 - and we've finished our program! When outputting many numbers it can get confusing for the user, so it might also be a nice idea for the application to number each score it outputs -- what better way to do this than make use of the index number! We've covered everything necessary to create this program - if you feel like a challenge, try to create it all by yourself, if not, feel free to take a look at the code I whipped up below (with a little bit of extra cout
polish).Executes a statement repeatedly until the condition becomes false. For information on the range-based for statement, see Range-based for Statement (C++).
Syntax
for (
init-expression;
cond-expression;
loop-expression)
statement
;
Remarks
Use the for statement to construct loops that must execute a specified number of times.
Dev Loop Full
The for statement consists of three optional parts, as shown in the following table. Antares auto-tune 8 native software download.
for Loop Elements
Syntax Name | When Executed | Description |
---|---|---|
init-expression | Before any other element of the for statement, init-expression is executed only once. Control then passes to cond-expression . | Often used to initialize loop indices. It can contain expressions or declarations. |
cond-expression | Before execution of each iteration of statement , including the first iteration. statement is executed only if cond-expression evaluates to true (nonzero). | An expression that evaluates to an integral type or a class type that has an unambiguous conversion to an integral type. Normally used to test for loop-termination criteria. |
loop-expression | At the end of each iteration of statement . After loop-expression is executed, cond-expression is evaluated. | Normally used to increment loop indices. |
The following examples show different ways to use the for statement.
init-expression
and loop-expression
can contain multiple statements separated by commas. For example:loop-expression
can be incremented or decremented, or modified in other ways.A for loop terminates when a break, return, or goto (to a labeled statement outside the for loop) within
statement
is executed. A continue statement in a for loop terminates only the current iteration.If
cond-expression
is omitted, it's considered true
, and the for loop won't terminate without a break, return, or goto within statement
.Again, the loop plays fine in the context of the song. The click is only added when it is saved as a remix sample. The files traktor 2.1.2 good loop vs traktor 2.10.3 bad loop are samples from the exact same loop in the exact same song. The only difference is the version of traktor used to capture them. Four decks, 30 DJ effects, remix decks and loop recording are the key features of the application. In addition, it converts each of the four decks into a remix deck, enabling you to load up to 16 loops and play four at a time. Traktor Pro 2 can excel as a team player amongst its peers. Jan 27, 2020 Forums Products TRAKTOR Area TRAKTOR PRO / TRAKTOR SCRATCH PRO Automatically activate loop when track comes to loop point. Discussion in. I sometime save more than 1 loop in a track so I probably wouldn't use it but then again I always save loops at the end of all my tracks for long mixes and I sometimes forget to activate them lol. Traktor pro 2 download with crack. Jan 01, 2013 Traktor has a built in sampler and as a result users are able to record loops ranging from a small 1/32th of a beat to a 32 bar loop. This loop can then be placed in a remix deck and used as a part of a remix set. As default Traktor is set to automatically save all loops into the track collection and saves them on your hard drive as a.wav file.
Although the three fields of the for statement are normally used for initialization, testing for termination, and incrementing, they're not restricted to these uses. For example, the following code prints the numbers 0 through 4. In this case,
statement
is the null statement:for Loops and the C++ Standard
The C++ standard says that a variable declared in a for loop shall go out of scope after the for loop ends. For example:
By default, under /Ze, a variable declared in a for loop remains in scope until the for loop's enclosing scope ends.
/Zc:forScope enables standard behavior of variables declared in for loops without needing to specify
/Za
.It's also possible to use the scoping differences of the for loop to redeclare variables under
/Ze
as follows:This behavior more closely mimics the standard behavior of a variable declared in a for loop, which requires variables declared in a for loop to go out of scope after the loop is done. When a variable is declared in a for loop, the compiler internally promotes it to a local variable in the for loop's enclosing scope. It's promoted even if there's already a local variable with the same name.
See also
Iteration Statements
Keywords
while Statement (C++)
do-while Statement (C++)
Range-based for Statement (C++)
Keywords
while Statement (C++)
do-while Statement (C++)
Range-based for Statement (C++)