Simple, beautiful CLI output for Haskell.

Build declarative and composable sections, trees, tables, dashboards for your Haskell applications. . Zero dependencies, rich text formatting with alignment, underlines, padding, margins. Features lists, trees, tables, charts, banners and more.

layoutz

Simple, beautiful CLI output for Haskell 🪶

Build declarative and composable sections, trees, tables, dashboards for your Haskell applications.

Features

• Zero dependencies, use Layoutz.hs like a header file
• Rich text formatting: alignment, underlines, padding, margins
• Lists, trees, tables, charts, banners...

Installation

Add to your package.yaml or .cabal file:

dependencies:
  - layoutz

Or install directly:

cabal install layoutz

All you need:

import Layoutz

Quickstart

Beautiful, compositional text layouts:

import Layoutz

demo = layout
  [ center $ row [text "Layoutz", underline' "ˆ" $ text "DEMO"]
  , br
  , row
    [ statusCard "Users" "1.2K"
    , statusCard' DoubleBorder "API" "UP"
    , statusCard' ThickBorder "CPU" "23%"
    , table' RoundBorder ["Name", "Role", "Status"] 
        [ [text "Alice", text "Engineer", text "Online"]
        , [text "Eve", text "QA", text "Away"]
        ]
    , section "Pugilists" [kv [("Kazushi", "Sakuraba"), ("Jet", "Li")]]
    ]
  ]

putStrLn $ render demo

                                Layoutz DEMO
                                        ˆˆˆˆ

┌─────────┐ ╔═══════╗ ┏━━━━━━━┓ ╭───────┬──────────┬────────╮ === Pugilists ===
│ Users   │ ║ API   ║ ┃ CPU   ┃ │ Name  │ Role     │ Status │ Kazushi: Sakuraba
│ 1.2K    │ ║ UP    ║ ┃ 23%   ┃ ├───────┼──────────┼────────┤ Jet:     Li
└─────────┘ ╚═══════╝ ┗━━━━━━━┛ │ Alice │ Engineer │ Online │
                                │ Eve   │ QA       │ Away   │
                                ╰───────┴──────────┴────────╯

Core concepts

• Every piece of content is an Element
• Elements are immutable and composable - build complex layouts by combining simple elements
• A layout arranges elements vertically:

layout [elem1, elem2, elem3]  -- Joins with "\n"

Call render on any element to get a string

The power comes from uniform composition - since everything has the Element typeclass, everything can be combined.

Elements

Text

text "Simple text"

Simple text

Line Break

Add line breaks with br:

layout [text "Line 1", br, text "Line 2"]

Line 1

Line 2

Section: section

section "Config" [kv [("env", "prod")]]
section' "-" "Status" [kv [("health", "ok")]]
section'' "#" "Report" 5 [kv [("items", "42")]]

=== Config ===
env: prod

--- Status ---
health: ok

##### Report #####
items: 42

Layout (vertical): layout

layout [text "First", text "Second", text "Third"]

First
Second
Third

Row (horizontal): row

row [text "Left", text "Middle", text "Right"]

Left Middle Right

Horizontal rule: hr

hr
hr' "~"
hr'' "-" 10

──────────────────────────────────────────────────
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
----------

Key-value pairs: kv

kv [("name", "Alice"), ("role", "admin")]

name: Alice
role: admin

Table: table

Tables automatically handle alignment and borders:

table ["Name", "Age", "City"] 
  [ [text "Alice", text "30", text "New York"]
  , [text "Bob", text "25", text ""]  -- Missing values handled
  , [text "Charlie", text "35", text "London"]
  ]

┌─────────┬─────┬─────────┐
│ Name    │ Age │ City    │
├─────────┼─────┼─────────┤
│ Alice   │ 30  │ New York│
│ Bob     │ 25  │         │
│ Charlie │ 35  │ London  │
└─────────┴─────┴─────────┘

Unordered Lists: ul

Clean unordered lists with automatic nesting:

ul [text "Feature A", text "Feature B", text "Feature C"]

• Feature A
• Feature B
• Feature C

Nested lists with auto-styling:

ul [ text "Backend"
   , ul [text "API", text "Database"]
   , text "Frontend"
   , ul [text "Components", ul [text "Header", ul [text "Footer"]]]
   ]

• Backend
  ◦ API
  ◦ Database
• Frontend
  ◦ Components
    ▪ Header
      • Footer

Underline: underline

Add underlines to any element:

underline $ text "Important Title"
underline' "=" $ text "Custom"

Important Title
───────────────

Custom
══════

Box: box

With title:

box "Summary" [kv [("total", "42")]]

┌──Summary───┐
│ total: 42  │
└────────────┘

Without title:

box "" [kv [("total", "42")]]

┌────────────┐
│ total: 42  │
└────────────┘

Status card: statusCard

statusCard "CPU" "45%"

┌───────┐
│ CPU   │
│ 45%   │
└───────┘

Progress bar: inlineBar

inlineBar "Download" 0.75

Download [███████████████─────] 75%

Tree: tree

tree "Project" 
  [ branch "src" 
      [ leaf "main.hs"
      , leaf "test.hs"
      ]
  , branch "docs"
      [ leaf "README.md"
      ]
  ]

Project
├── src
│   ├── main.hs
│   └── test.hs
└── docs
    └── README.md

Chart: chart

chart [("Web", 10), ("Mobile", 20), ("API", 15)]

Web    │████████████████████ 10
Mobile │████████████████████████████████████████ 20
API    │██████████████████████████████ 15

Padding: pad

Add uniform padding around any element:

pad 2 $ text "content"

        
        
  content  
        
        

Centering: center

Smart auto-centering and manual width:

center $ text "Auto-centered"     -- Uses layout context
center' 20 $ text "Manual width"  -- Fixed width

        Auto-centered        

    Manual width    

Margin: margin

Use margin for colorful "compiler-style" prefixes:

layout
  [ marginError [text "Type error: expected Int, got String"]
  , marginWarn [text "Unused variable 'temp'"] 
  , marginSuccess [text "Build completed successfully"]
  , marginInfo [text "Pro tip: Use layoutz for beautiful output"]
  ]

[error] Type error: expected Int, got String
[warn] Unused variable 'temp'
[success] Build completed successfully
[info] Pro tip: Use layoutz for beautiful output

Border Styles

Elements like box, table, and statusCard support different border styles:

NormalBorder (default):

box "Title" [text "content"]

┌──Title──┐
│ content │
└─────────┘

DoubleBorder:

statusCard' DoubleBorder "API" "UP"

╔═══════╗
║ API   ║
║ UP    ║
╚═══════╝

ThickBorder:

table' ThickBorder ["Name"] [[text "Alice"]]

┏━━━━━━━┓
┃ Name  ┃
┣━━━━━━━┫
┃ Alice ┃
┗━━━━━━━┛

RoundBorder:

box' RoundBorder "Info" [text "content"]

╭──Info───╮
│ content │
╰─────────╯

REPL Usage

Drop into GHCi to experiment:

cabal repl

λ> import Layoutz
λ> putStrLn $ render $ center $ box "Hello" [text "World!"]
┌──Hello──┐
│ World!  │
└─────────┘
λ> putStrLn $ render $ table ["A", "B"] [[text "1", text "2"]]
┌───┬───┐
│ A │ B │
├───┼───┤
│ 1 │ 2 │
└───┴───┘

Inspiration

• Original Scala layoutz.