Problem 57775. Easy Sequences 102: One-line Code Challenge - Take While Function

takeWhile is another useful functional programming construct. The takewhile function is similar to the built-in function arrayfun, but unlike arrayfun, takewhile is applied to an input array of indefinite length.
We shall define takeWhile as a function that accepts 2 function handle and an integer as inputs, and outputs a row vector. The first function input, A, defines a sequence with the natural numbers as domain. The second function input C, is a conditional function, while the third argument n, is the starting number. takeWhile applies A to all consecutive positive numbers starting with n, as long as the condition in C is met and stops as soon as C is no longer satisfied.
The following examples will make this concept clearer:
>> % Example #1
>> A = @(x) 2*x; C = @(y) y < 30;
>> takeWhile(A,C,5)
>> ans =
>> 10 12 14 16 18 20 22 24 26 28
>>
>> % Example #2
>> A = @(x) cosd(10*x) + 1; C = @(y) y >= 1;
>> takeWhile(A,C,1)
>> ans =
>> 1.9848 1.9397 1.8660 1.7660 1.6428 1.5000 1.3420 1.1736 1.0000
In the first example, function A outputs the set of even numbers starting from 10, but function C limits the output to only those that are less than 30.
In the second example, the trigonometric function A, is applied while the value of the A is greater than or equal to 1. A is applied to n = 1 to 9 and then takeWhile stops, since if n = 10, A = cosd(10*10)+1 = 0.8264 < 1.
In this problem we are asked to implement the takeWhile function, with the following restrictions:
  • The function should only have one (1) line of code, excluding the function start line.
  • Semicolons (;) are considered end-of-line characters.
  • Please suppress the function end line. Keyword 'end' is not allowed.
  • Regular expressions and string manipulation are not allowed.
Solve

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Last Solution submitted on Apr 28, 2024

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