Weekly Review — Month 1 · Week 2 (Days 008–014)

Journal index · Roadmap › Week 2

📅 The Week in One Line

Got fluent with Go's composite types — slices (and their backing-array gotchas), maps/sets, strings/runes, and structs with tags.

✅ What I Completed

• Day 008 — Arrays & slice basics (len/cap)
• Day 009 — Slice internals: backing array, append & aliasing
• Day 010 — Slice tricks: filter, insert, delete, copy
• Day 011 — Maps & sets, comma-ok, ordered iteration
• Day 012 — Strings, runes, bytes & UTF-8
• Day 013 — Structs & struct tags
• Day 014 — Review & closed-book recall
• Examples: slice-internals, slice-tricks, maps-sets, strings-runes, structs-tags
• Exercises solved: 3 (wordfreq, dedup, runereverse) — all with table-driven tests

💡 Lessons Learned

• A slice is a (pointer, len, cap) view; arrays are copied values.
• append writes in place when capacity allows (aliasing!) and reallocates when it doesn't — always s = append(s, …).
• The 3-index slice s[i:j:j] and copy/make are the tools to break aliasing.
• comma-ok separates "missing key" from "zero value"; writing a nil map panics.
• Map iteration is randomized — sort keys for deterministic output.
• Strings are immutable UTF-8 bytes: index → byte, range → rune; reverse by []rune.
• Pointer receivers mutate; value receivers copy. Struct tags drive encoding/json, and only exported fields are serialized.

💪 Strengths (what clicked)

• Maps/sets and the comma-ok idiom felt natural immediately.
• Table-driven tests are now a reflex for every exercise.

🧩 Weaknesses (what's still fuzzy)

• Predicting cap growth and reasoning about aliasing under nested appends.
• Remembering to reach for the slices/maps stdlib helpers instead of hand-rolling.

🔁 Spaced-Repetition Re-quiz (topics from earlier weeks)

1. Q: (Wk1) Why is string(65) "A" and not "65"?
   A

   It converts an int to a rune/code point; use strconv.Itoa for digits.
2. Q: (Wk1) defer order and arg-evaluation timing?
   A

   LIFO; arguments are evaluated at the defer statement.
3. Q: (Wk2) When does append reallocate the backing array?
   A

   When capacity is exhausted; otherwise it writes in place and may alias other slices.
4. Q: (Wk2) Zero value of a map, and what happens if you write to it?
   A

   nil; writing to a nil map panics — make it first.

🎯 Action Items

• Refactor the slice exercises to use slices.Delete/slices.Clone and compare.
• Re-read the slices cheatsheet before Week 3.
• Add one Exercism "strings" exercise for extra rune/byte reps.

🚀 Next Week Goals

• Methods & receivers (value vs pointer), interfaces (implicit satisfaction, method sets, the nil-interface trap), and idiomatic error handling (%w, errors.Is/As).

📊 Metrics

Hours	Days hit	Exercises	Commits	Avg confidence
10	7/7	3	7	3.⅘

Suggested commit: docs(journal): week 2 review