Get previous true value from a given array index in Julia | Array findprev() Method Last Updated : 12 Jul, 2025 Summarize Comments Improve Suggest changes Share Like Article Like Report The findprev() is an inbuilt function in julia which is used to return the previous index before or including i of a true element of the specified array A, or returns zero if true value is not found. Here values of index or key start from 1 i.e, for index of 1st element is 1, index of 2nd element is 2 and so on. Syntax: findprev(A, i) or findprev(predicate::Function, A, i) Parameters: A: Specified array i: Specified value Predicate Function: Determines whether something is true or false based on the specified arguments Returns: It returns the previous index before or including i of a true element of the specified array A, or returns zero if true value is not found. Example 1: Python # Julia program to illustrate # the use of Array findprev() method # Finding index of previous true value # before or including index 1 from # the 1D array A A = [false, true, true, false] println(findprev(A, 2)) # Finding index of previous true value # before or including index (1, 1) from # the 2D array B of size 2 * 2 B = [true false; true false] println(findprev(B, CartesianIndex(1, 1))) # Finding index of previous true value # before or including index (1, 2, 1) from # the 3D array C of size 2 * 2*2 C = cat([true false; true false], [false true; true false], [true false; true true], dims = 3) println(findprev(C, CartesianIndex(1, 2, 1))) Output: Example 2: Python # Julia program to illustrate # the use of Array findprev() method # Finding index of previous even value # before or including index 3 from # the 1D array A A = [1, 2, 5, 6] println(findprev(iseven, A, 3)) # Finding index of previous even value # before or including index (2, 2) from # the 2D array B of size 2 * 2 B = [3 5; 6 7] println(findprev(iseven, B, CartesianIndex(2, 2))) # Finding index of previous even value # before or including index (2, 2, 1) from # the 3D array C of size 2 * 2*2 C = cat([1 2; 3 4], [5 6; 7 8], [9 10; 11 12], dims = 3) println(findprev(iseven, C, CartesianIndex(2, 2, 1))) Output: Comment More infoAdvertise with us Next Article Get index of first true value of array in Julia | Array findfirst() Method K Kanchan_Ray Follow Improve Article Tags : Julia Julia Array-functions Similar Reads Get next true value from a given array index in Julia | Array findnext() Method The findnext() is an inbuilt function in julia which is used to return the next coming index after or including i of a true element of the specified array A, or returns zero if true value is not found. Here values of index or key start from 1 i.e, for index of 1st element is 1, index of 2nd element 2 min read Get index of first true value of array in Julia | Array findfirst() Method The findfirst() is an inbuilt function in julia which is used to return the index or key of the first true value in the specified array. Here values of index or key start from 1 i.e, for index of 1st element is 1, index of 2nd element is 2 and so on. Syntax: findfirst(A) or findfirst(predicate::Func 2 min read Get index of last true value of array in Julia | Array findlast() Method The findlast() is an inbuilt function in julia which is used to return the index or key of the last true value in the specified array. Here values of index or key start from 1 i.e, for index of 1st element is 1, index of 2nd element is 2 and so on. Syntax: findlast(A) or findlast(predicate::Function 2 min read Set elements at a given index of array in Julia - setindex!() Method The setindex!() is an inbuilt function in julia which is used to store values from the given array X within some subset of A as specified by inds. Syntax: setindex!(A, X, inds...) Parameters: A: Specified function.X: Specified array.inds: Specified index. Returns: It does not return any values. 1 min read Checking for true values in an array in Julia - any() and all() Methods The any() is an inbuilt function in julia which is used to test whether any elements of the specified boolean collection are true and if any of the input value is 'missing', it will return missing if all non-missing values are false. Syntax: any(itr) Parameters: itr: Specified boolean collection. Re 2 min read Get all array elements with true values in Julia | Array findall() Method The findall() is an inbuilt function in julia which is used to return a vector of indices or keys of the all true values from the specified array A. If such true values are not present in the array, return an empty array. Here values of index or key start from 1 i.e, for index of 1st element is 1, i 2 min read Like