Скачать или смотреть Generate a Fibonacci Sequence up to a Specified Maximum Number in Haskell

Learn how to efficiently generate a `Fibonacci sequence` in Haskell that produces numbers up to a maximum value.
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Generating a Fibonacci Sequence in Haskell up to a Maximum Number

The Fibonacci sequence, a series of numbers where each number is the sum of the two preceding ones, is a popular topic in programming, especially when it comes to learning a new language like Haskell. If you're working with Haskell and need to generate a Fibonacci sequence that outputs numbers up to a specified maximum, you're in the right place! Let's dive into the problem and its solution to help you produce the correct Fibonacci sequence.

Understanding the Problem

You might encounter a situation where your current Haskell implementation is set to output a specific number of terms in the Fibonacci sequence, but you want it to generate Fibonacci numbers up to a certain maximum value. For example, calling your function fibonacciSequence 86 should yield numbers like 1, 1, 2, 3, 5, 8—all of which are less than or equal to 86. However, an incorrect implementation may return a static list of the first 10 Fibonacci numbers instead.

Breaking Down the Original Code

Here's the code you started with, which is designed to generate Fibonacci numbers, but it produces results limited to the first 10 Fibonacci numbers:

[[See Video to Reveal this Text or Code Snippet]]

What's Wrong

The code uses map fib [1..n], which generates a list of Fibonacci numbers based on their position but does not respect an upper limit value.

It prints out Fibonacci numbers only from the first 10 positions rather than up to a specified maximum value.

Crafting the Correct Solution

To generate Fibonacci numbers up to a maximum specified number, we can take advantage of Haskell's functional programming features. Let’s see the changes we can make:

Implementing the Solution

Here’s a corrected version of the code that will create a Fibonacci sequence up to a predefined maximum number:

[[See Video to Reveal this Text or Code Snippet]]

Explanation of Changes

Define maxFibonacci: We introduce a new function maxFibonacci that takes a maximum value and uses takeWhile to filter Fibonacci numbers that are less than or equal to this value.

Infinite List of Fibonacci Numbers: fibList is defined as an infinite list of Fibonacci numbers generated using the previously defined fib function.

Dynamic Output: When calling the maxFibonacci function in main, we dynamically produce the Fibonacci numbers up to the maximum specified.

Conclusion

With these changes, you’ll have a function that effectively generates a Fibonacci sequence according to your needs, outputting numbers only up to the specified maximum. Now you can generate beautiful Fibonacci sequences using Haskell without any constraints on how many terms to display—just limit them by their value instead!

Feel free to modify the max variable to test with different values and explore the rich world of Fibonacci numbers in Haskell!