go-itergen解决了Go一个常规而又非常重要的问题：没有映射，没有过滤器，什么都没有。如果你是函数式背景会感到非常苦恼，现在got-itergen提供Go的常规函数生成功能，为可迭代的类型生成常规函数，比如map和filter。
go-itergen支持的操作：
Map
Filter
All
Some
Concat
Find
ForEach
Reverse
Splice
Reduce
生成代码：
//go:generate go-itergen -t "float64" --pkg="mypkg" --map="string" --map="int" --filter --all --some --foreach --concat --find --reverse --splice --reduce="string" --reduce="int"代码示例：
package mypkgimport ( "errors")type Float64Iter []float64func NewFloat64Iter(items ...float64) Float64Iter { return Float64Iter(items)}type Float64IterMapResult []interface{}func (i Float64Iter) Map(fn func(int, float64) interface{}) Float64IterMapResult { var result []interface{} for n, item := range i { result = append(result, fn(n, item)) } return result}var ErrFloat64ToFloat64 = errors.New("cannot convert Float64IterMapResult to []float64")func (r Float64IterMapResult) Iter() (Float64Iter, error) { var result []float64 for _, i := range r { if _, ok := i.(float64); !ok { return nil, ErrFloat64ToFloat64 } result = append(result, i.(float64)) } return Float64Iter(result), nil}var ErrFloat64ToString = errors.New("cannot convert Float64IterMapResult to []string")func (r Float64IterMapResult) ToString() ([]string, error) { var result []string for _, i := range r { if _, ok := i.(string); !ok { return nil, ErrFloat64ToString } result = append(result, i.(string)) } return result, nil}var ErrFloat64ToInt = errors.New("cannot convert Float64IterMapResult to []int")func (r Float64IterMapResult) ToInt() ([]int, error) { var result []int for _, i := range r { if _, ok := i.(int); !ok { return nil, ErrFloat64ToInt } result = append(result, i.(int)) } return result, nil}func (i Float64Iter) Filter(fn func(float64) bool) Float64Iter { var result []float64 for _, item := range i { if fn(item) { result = append(result, item) } } return Float64Iter(result)}func (i Float64Iter) All(fn func(float64) bool) bool { for _, item := range i { if !fn(item) { return false } } return true}func (i Float64Iter) Some(fn func(float64) bool) bool { for _, item := range i { if fn(item) { return true } } return false}func (i Float64Iter) ForEach(fn func(int, float64) interface{}) { for n, item := range i { fn(n, item) }}func (i Float64Iter) Concat(i2 Float64Iter) Float64Iter { return append(i, i2...)}func (i Float64Iter) Find(fn func(float64) bool) (float64, int) { var zero float64 for i, item := range i { if fn(item) { return item, i } } return zero, -1}func (i Float64Iter) Reverse() Float64Iter { var result []float64 for j := len(i) - 1; j >= 0; j-- { result = append(result, i[j]) } return result}// Splice removes numDelete items from the slice// since start. If numDelete is -1 it will delete all// items after start. If start is higher than the// slice length or lower than 0 the whole slice// will be returned.func (i Float64Iter) Splice(start, numDelete int) Float64Iter { var result Float64Iter length := len(i) if start >= length-1 || start < 0 { return i } result = append(result, i[:start]...) if numDelete > -1 && numDelete+start < length { result = append(result, i[start+numDelete:]...) } return result}func (i Float64Iter) ReduceInt(fn func(current float64, acc int, index int) int, initial int) int { var result = initial for idx, item := range i { initial = fn(item, result, idx) } return result}func (i Float64Iter) ReduceString(fn func(current float64, acc string, index int) string, initial string) string { var result = initial for idx, item := range i { initial = fn(item, result, idx) } return result}func main() { rounded, err := NewFloat64Iter(1.2, 2.4, 3.5, 5.6).Filter(func(n float64) bool { return n > 2.0 }).Map(func(int i, n float64) interface{} { return int(n) }).ToInt() fmt.Println(rounded) // [3 5]}
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