On the other hand, “For” loops are used when the iteration numbers are known. We can use list comprehension with the same condition that we used in the exercise in the first section.So, it is easy to say that the user can use the “While” loop when he/she does not have any idea regarding the number of iterations. There are more efficient ways to create this array. julia> for i in 1:length(x), j in 1:length(y) In this case, we use the indices 1:length(x) for x and 1:length(y) for y. Now we have to use proper indices to fill A. The element type specification can be omitted since the default value type is Float64. Nevertheless, it is a useful syntax in many cases.įirst, we have to define vectors x and y, and an empty array of the proper size and element type to use in nested loops. There are other limitations of the shorter syntax, such as the impossibility to perform any operation outside the inner loop. On the other hand, if we use the shorter syntax, the break keyword breaks both loops. If we use the traditional syntax and the break keyword inside the inner loop, it breaks only the inner loop. The main difference is when using the break keyword. Julia allows for an additional shorter syntax: julia> for i in 1:3, j in (i, j)Įven though the output is the same, this syntax is not equivalent to the previous one. This style of writing nested loops is typical in other languages. The range of the inner loop depends on the variable i from the outer loop. In Julia, nested loops can be created in a similar way as in other languages. However, we must use || instead of & because we want to use the continue keyword. To check that the integer is divisible, we use the same condition as before. We used the short-circuit evaluation to break the loop. Because the variable i represents an integer and we want to iterate over integers between 1 and 100, the correct termination condition is i > 100. The true value creates an infinite loop, i.e., it is necessary to end the loop with the break keyword. The code after the continue keyword is not evaluated. The following code prints all even numbers from 1 to 10. julia> for i in 1:100Ī while loop can be created in a similar way julia> i = 0 Īnother useful feature is to skip elements using the continue keyword. When we know how to check the conditions, it is easy to write a for loop to iterate over integers from 1 to 100. Julia> mod(i, 3) = mod(i, 7) = 0 & println("$(i) is divisible by 3 and 7") Or using the short-circuit evaluation julia> i = 21 This can be performed using the mod function in combination with the if-else statement as follows: julia> i = 21 Println("Hi, my name is $name and I am $age old.")įirst, we need to check if a given integer is divisible by both 3 and 7. In such a case, we get a tuple of the key and the corresponding value in each iteration. It is also possible to iterate over other data structures such as dictionaries. This is advantageous because it allows getting elements of iterable objects directly without using indices. In Julia (similarly to Python), it is possible to loop not only over ranges but over any iterable object such as arrays or tuples. Regardless of which notation is used, it is essential to be consistent and use the same notation in all for loops. However, it is better to use the in keyword to improve code readability. It is possible to use the = or ∈ symbol instead of the in keyword. There are two alternative notations for the for loop. The following example iterates over all integers from 1 to 5, and in each iteration, we use the macro to print the current value of the variable i. The for loops are created similarly to Matlab. Julia> while i a, b, c = 1, "hello", :world If the condition is false before the first iteration, the whole while loop is skipped. If the condition is false, the while loop is terminated. The while loop evaluates the condition, and as long it remains true, it evaluates the body of the while loop. A typical example is performing operations on array elements. Loops are useful to repeat the same computation multiple times with different values. for and while loopsĪs in other languages, Julia supports two basic constructs for repeated evaluation: while and for loops. While if conditions are evaluated only once, loops are assessed multiple times. Linear regression with sparse constraints.Introduction to regression and classification.Introduction to continuous optimization.
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