lof

README

lof: lower-order function wrappers

Utility functions for functional programming. Wraps Go builtins for HOF use, plus helpers for common patterns.

A lower-order function is the flip side of a higher-order function—the function being passed, not the one receiving it.

Go builtins like len are operators, not functions—you can't pass len to ToInt. lof wraps them as passable functions.

names.Each(lof.Println)  // print each name

See pkg.go.dev for complete API documentation.

Quick Start

import (
    "github.com/binaryphile/fluentfp/lof"
    "github.com/binaryphile/fluentfp/slice"
)

names := slice.From(users).ToString(User.Name)
names.Each(lof.Println)  // print each name

// When type has no Len() method, lof.Len bridges the gap
type Report struct { Pages []Page }

// pageCount returns the number of pages in a report.
pageCount := func(r Report) int { return lof.Len(r.Pages) }
pageCounts := slice.From(reports).ToInt(pageCount)

API Reference

Function	Signature	Purpose	Example
Len	Len[T]([]T) int	Wrap len for slices	lengths = items.ToInt(lof.Len)
StringLen	StringLen(string) int	Wrap len for strings	lens = names.ToInt(lof.StringLen)
Println	Println(string)	Wrap fmt.Println	names.Each(lof.Println)
IfNotEmpty	IfNotEmpty(string) (string, bool)	Comma-ok for strings	diff, ok := lof.IfNotEmpty(result)

IfNotEmpty: Comma-ok for Empty Strings

Some functions use empty string as "absent" (e.g., cmp.Diff returns "" when equal). IfNotEmpty converts this to Go's comma-ok idiom.

result := cmp.Diff(want, got)
if diff, ok := lof.IfNotEmpty(result); ok {
    t.Errorf("mismatch:\n%s", diff)
}

When NOT to Use lof

• Method expressions exist — User.Name beats wrapping a getter
• Direct calls work — If you're not in a HOF chain, just call len() or fmt.Println()

See Also

For the HOF methods that consume these wrappers, see slice.

Documentation

Overview

Package lof provides utility functions for functional programming.

Index

• func IfNotEmpty(s string) (string, bool)
• func Len[T any](ts []T) int
• func Println(s string)
• func StringLen(s string) int

Functions

func IfNotEmpty

func IfNotEmpty(s string) (string, bool)

IfNotEmpty returns s and whether s is non-empty. Converts "empty string = absent" returns to Go's comma-ok idiom.

result := cmp.Diff(want, got)
if diff, ok := lof.IfNotEmpty(result); ok {
    t.Errorf("mismatch:\n%s", diff)
}

func Len

func Len[T any](ts []T) int

Len wraps the len builtin for slices.

func Println

func Println(s string)

Println wraps fmt.Println for strings.

func StringLen

func StringLen(s string) int

StringLen wraps the len builtin for strings.