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# iter — Lazy Iterators with Generics for Go

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`iter` is a library of lazy iterators for Go. Built on pure functions, no unnecessary allocations, with full generics support and a clean functional style.

Apply transformations like `Map`, `Filter`, `Take`, `Fold`, `Zip` directly to sequences — lazily and efficiently.

---

## 📦 Installation

```bash
go get github.com/enetx/iter
```

---

## 🚀 Example

```go
package main

import (
	"fmt"
	"github.com/enetx/iter"
)

func main() {
	// Extract even numbers and square them:
	s := iter.FromSlice([]int{1, 2, 3, 4, 5})
	s = iter.Filter(s, func(x int) bool { return x%2 == 0 })        // 2, 4
	s = iter.Map(s, func(x int) int { return x * x })              // 4, 16
	out := iter.ToSlice(s)
	fmt.Println(out) // [4 16]
}
```

---

## ✨ Features

- ✅ **Lazy sequences** — transformations are not applied until iteration begins.
- ✅ **Generics-powered** — works with any types `T`, `U`, structs, etc.
- ✅ **Zero-allocation** — avoids unnecessary memory allocations.
- ✅ **Functional API** — each transformation is a pure function: `Map`, `Filter`, `Take`, `Skip`, `StepBy`, `Flatten`, `Zip`, `Enumerate`, `Fold`, `Reduce`, and many more.
- ✅ **Supports pairs, maps, channels** — `Seq2`, `FromMap`, `FromChan`, and beyond.

---

## 🔬 More Examples

```go
// Simple range with step
r := iter.Iota(1, 10) // 1..9
r = iter.StepBy(r, 3)  // 1, 4, 7
fmt.Println(iter.ToSlice(r)) // → [1 4 7]

// Iterate over a map
m := map[string]int{"a": 1, "b": 2}
s2 := iter.FromMap(m)
iter.ForEach2(s2, func(k string, v int) {
	fmt.Printf("%s → %d\n", k, v)
})
```

---

## ⚖️ License

MIT
