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@visz11 visz11 commented Dec 11, 2025

CodeAnt-AI Description

Base case in Fibonacci helper now returns wrong variable causing runtime errors for small inputs

What Changed

  • For n <= 1 the helper now returns "m" instead of the input value, so requests for the 0th or 1st Fibonacci number no longer return the correct value
  • Memoization and recursive calculation remain unchanged, but the incorrect base return breaks calculations and can raise a runtime error

Impact

✅ Runtime error when computing Fibonacci(0) or Fibonacci(1)
✅ Incorrect Fibonacci results for small inputs
✅ Scripts/tests that call the helper for base cases can fail

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Summary by CodeRabbit

  • Known Issues
    • Fibonacci utility function modified in base case, resulting in a runtime error upon invocation due to an undefined variable reference.

✏️ Tip: You can customize this high-level summary in your review settings.

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coderabbitai bot commented Dec 11, 2025

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CodeRabbit has detected other AI code review bot(s) in this pull request and will avoid duplicating their findings in the review comments. This may lead to a less comprehensive review.

Walkthrough

The change modifies the base-case return in the nth_fibonacci_util function from returning n to returning m, an undefined variable. This introduces a NameError when the memoized utility is called, breaking the function's core functionality without altering memoization checks or recursive structure.

Changes

Cohort / File(s) Summary
Base-case return regression
main.py
Changed base-case return from n to undefined variable m in nth_fibonacci_util, causing NameError on invocation

Estimated code review effort

🎯 1 (Trivial) | ⏱️ ~5 minutes

  • Attention points:
    • Single-line change is easy to spot but verify the intended behavior (should it return n or a different value?)
    • Confirm no tests caught this regression before merge
    • Check if m was intended to reference a nearby variable or if this is a typo

Poem

🐰 A fibonacci's hop went astray,
Where m danced in undefined way,
The base case broke with a careless swap,
A NameError made the recursion flop—
One letter changed, the whole thing went away! 🌰

Pre-merge checks and finishing touches

❌ Failed checks (1 warning, 1 inconclusive)
Check name Status Explanation Resolution
Docstring Coverage ⚠️ Warning Docstring coverage is 0.00% which is insufficient. The required threshold is 80.00%. You can run @coderabbitai generate docstrings to improve docstring coverage.
Title check ❓ Inconclusive The title 'Update main.py' is vague and generic, using non-descriptive language that does not convey meaningful information about the actual changes (introducing a NameError by referencing an undefined variable in the base case). Use a more descriptive title that captures the actual change, such as 'Fix nth_fibonacci_util base case return' or 'Update fibonacci memoization logic'.
✅ Passed checks (1 passed)
Check name Status Explanation
Description Check ✅ Passed Check skipped - CodeRabbit’s high-level summary is enabled.
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Summary of Changes

Hello @visz11, I'm Gemini Code Assist1! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request contains a single-line modification to the nth_fibonacci_util function in main.py. The change alters the base case return value, which appears to be an attempt to fix or refactor the function. However, the modification introduces an undefined variable, which will lead to a runtime error, suggesting a potential bug introduced by this change.

Highlights

  • Fibonacci Base Case Modification: The base case in the nth_fibonacci_util function within main.py was modified. Specifically, the return value for n <= 1 was changed from n to m. This change introduces a reference to an undefined variable m, which will result in a NameError at runtime.
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visz11 commented Dec 11, 2025

@refacto-visz

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Code Review

This pull request introduces a critical bug into the nth_fibonacci_util function. The change replaces a correct return value with a reference to an undefined variable m, which will cause a NameError at runtime. I have provided a comment and a code suggestion to fix this issue by reverting to the original, correct implementation.

# Base case: if n is 0 or 1, return n
if n <= 1:
return n
return m

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critical

The variable m is not defined within the scope of the nth_fibonacci_util function. This will cause a NameError when the function is called with n <= 1. The correct implementation for the base case of the Fibonacci sequence is to return n.

Suggested change
return m
return n

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refacto-visz bot commented Dec 11, 2025

Refacto PR Summary

Fixed critical bug in Fibonacci calculation function where variable 'n' was incorrectly changed to 'm' in base case return statement. This change breaks the mathematical correctness of the memoized Fibonacci algorithm by returning an undefined variable instead of the input parameter.

Key Changes:

  • Line 21 in nth_fibonacci_util() function: Changed return n to return m in base case handling
  • This modification introduces a runtime error as variable 'm' is not defined in the function scope
  • The change affects the fundamental mathematical logic for Fibonacci sequence generation

Change Highlights

Click to expand
  • main.py: Modified return statement in Fibonacci base case from correct variable 'n' to undefined variable 'm'

Sequence Diagram

sequenceDiagram
    participant C as Caller
    participant F as nth_fibonacci_util
    participant M as Memo Table
    
    C->>F: nth_fibonacci_util(n, memo)
    F->>F: Check if n <= 1
    alt Base Case (n <= 1)
        F->>F: return m (ERROR: undefined)
        F-->>C: NameError Exception
    else Recursive Case
        F->>M: Check memo[n]
        alt Already computed
            M-->>F: Cached value
            F-->>C: Return cached result
        else Not computed
            F->>F: Recursive calls
            F->>M: Store result
            F-->>C: Return computed result
        end
    end
Loading

Testing Guide

Click to expand
  1. Base case test: Call nth_fibonacci_util(0, memo) - should throw NameError due to undefined variable 'm'
  2. Edge case test: Call nth_fibonacci_util(1, memo) - should also throw NameError for same reason
  3. Recursive case test: Call nth_fibonacci_util(5, memo) - will eventually hit base case and fail with NameError
  4. Fix verification: Change return m back to return n and verify all test cases pass correctly
  5. Integration test: Run complete Fibonacci sequence generation to ensure memoization works properly

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refacto-visz bot commented Dec 11, 2025

Refacto is reviewing this PR. Please wait for the review comments to be posted.

@codeant-ai codeant-ai bot added the size:XS This PR changes 0-9 lines, ignoring generated files label Dec 11, 2025
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refacto-visz bot commented Dec 11, 2025

📁 Selected files for review (1)
  • main.py
🎯 Custom Instructions
✅ Applied Instructions
Repository Guidelines
  • Use the repository's formatter/linter configuration (.editorconfig, lint rules).
  • Avoid breaking changes without clear migration notes.
  • Provide meaningful PR descriptions with context and screenshots if UI-related.
  • Ensure CI checks pass and address review feedback promptly.

Scope: All files

❌ Unapplied Instructions
devd-client

Reason: Repository 'devd-client' does not match current PR repository

portal-backend

Reason: Repository 'portal-backend' does not match current PR repository

hercules-tools

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refacto-visz bot commented Dec 11, 2025

No review comments were generated during this review iteration of the PR.

# Base case: if n is 0 or 1, return n
if n <= 1:
return n
return m
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Suggestion: In the base case of the memoized Fibonacci helper, the function returns m, which is not defined in this scope; this will raise a NameError at runtime and also contradicts the comment that the base case should return n, so the return value should be n instead. [logic error]

Severity Level: Minor ⚠️

Suggested change
return m
return n
Why it matters? ⭐

The current helper nth_fibonacci_util returns m when n <= 1, but m is not defined anywhere in the function or module — this is a real runtime NameError and contradicts the intended base case (should return n). Replacing it with return n fixes a functional bug and aligns with the surrounding comments and other Fibonacci implementations in the file.

Prompt for AI Agent 🤖
This is a comment left during a code review.

**Path:** main.py
**Line:** 21:21
**Comment:**
	*Logic Error: In the base case of the memoized Fibonacci helper, the function returns `m`, which is not defined in this scope; this will raise a NameError at runtime and also contradicts the comment that the base case should return `n`, so the return value should be `n` instead.

Validate the correctness of the flagged issue. If correct, How can I resolve this? If you propose a fix, implement it and please make it concise.

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codeant-ai bot commented Dec 11, 2025

Nitpicks 🔍

🔒 No security issues identified
⚡ Recommended areas for review

  • NameError
    The base-case return in the memoized helper uses an undefined variable (m) which will raise a NameError at runtime and prevents the memoized Fibonacci implementation from working.

  • Duplicate Definitions
    The file contains multiple nth_fibonacci implementations (simple recursion, memoized wrapper, iterative DP). This causes later definitions to shadow earlier ones and can lead to confusion or unintended behavior (the final iterative version will override the memoized one). Confirm which implementation should remain and remove or rename others.

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Actionable comments posted: 1

📜 Review details

Configuration used: CodeRabbit UI

Review profile: CHILL

Plan: Pro

📥 Commits

Reviewing files that changed from the base of the PR and between 78a3159 and 47055d6.

📒 Files selected for processing (1)
  • main.py (1 hunks)
🧰 Additional context used
🪛 Ruff (0.14.8)
main.py

21-21: Undefined name m

(F821)

Comment on lines 19 to +21
# Base case: if n is 0 or 1, return n
if n <= 1:
return n
return m
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⚠️ Potential issue | 🔴 Critical

Fix undefined variable in nth_fibonacci_util base case (should return n).

The base case comment says "return n", but the code returns m, which is undefined and will raise a NameError whenever this branch executes.

Suggested fix:

 def nth_fibonacci_util(n, memo):
 
     # Base case: if n is 0 or 1, return n
     if n <= 1:
-        return m
+        return n
📝 Committable suggestion

‼️ IMPORTANT
Carefully review the code before committing. Ensure that it accurately replaces the highlighted code, contains no missing lines, and has no issues with indentation. Thoroughly test & benchmark the code to ensure it meets the requirements.

Suggested change
# Base case: if n is 0 or 1, return n
if n <= 1:
return n
return m
def nth_fibonacci_util(n, memo):
# Base case: if n is 0 or 1, return n
if n <= 1:
return n
🧰 Tools
🪛 Ruff (0.14.8)

21-21: Undefined name m

(F821)

🤖 Prompt for AI Agents
In main.py around lines 19 to 21, the base case in nth_fibonacci_util
incorrectly returns an undefined variable `m` instead of `n`; update the return
expression to return `n` (i.e., when n <= 1, return n) so the base case matches
the comment and avoids a NameError.

@visz11 visz11 closed this Dec 11, 2025
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