ff-euler-ffp

name	ff-euler-ffp
description	Use when editing or debugging Project Euler programs in ff/euler/*.ffp, including preserving prompt data, implementing algorithmic solutions, and validating with the Node/Deno preprocessor runtime.

f-flat-minor Euler Workflow

Use this skill for work in ff/euler/*.ffp.

Tool bootstrap

• Use mise x -- ... for commands that depend on repo-managed tools such as node, bun, deno, npm, and chomp.
• If a managed tool is missing, run mise install once from the repo root, then retry the command with mise x -- ....
• Do not switch runtimes just because a bare command is missing from PATH.

Core rules

1. Always solve algorithmically.

• Do not replace a Project Euler solution with a precomputed constant.
• Keep the original constraints and implement the actual algorithm in f-flat-minor words.

2. Verify the exact prompt and input data first.

• Confirm the exact Euler problem statement and required literals before editing.
• Preserve long digit/grid content exactly, including ordering.

3. Run .ffp with Node or Deno.

• Python python/execute.py does not preprocess .ffp.
• Preferred commands:

mise x -- node node/bin/ff-run.ts ff/euler/<file>.ffp
mise x -- node node/bin/ff-run.ts -t ff/euler/<file>.ffp

Runtime gotchas

• Avoid multiline string literals in Euler files; keep long numeric strings as a single quoted token.
• pick is not guaranteed in core; implement a local equivalent if needed.
• Queue behavior is fragile in deep helpers: q< moves top of stack to queue, q> restores from queue.

Debugging workflow

1. Validate helper stack effects in tiny probes (for example, temporary files in /tmp).
2. Prove helper words independently before full-scan recursion.
3. Use trace mode for stack underflow and ordering bugs:

mise x -- node node/bin/ff-run.ts -t ff/euler/<file>.ffp

4. In scan solutions, confirm cleanup only drops dataset values, not the computed result.
5. If preserving a result across bulk drop, move it aside with q< ... q>.

Build order for scan-style solutions

1. Parse/representation helpers
2. Single-position directional checks
3. Max-update logic with explicit stack-shape checks
4. Full scan recursion
5. Final cleanup and output