yi - I Ching (Book of Changes) Library for Go

A Go library for I Ching (Book of Changes) hexagram calculation and divination, providing complete functionality for hexagram generation, transformation, Five Elements (WuXing), Sexagenary Cycle (JiaZi), Six Relations (LiuQin), Shi-Ying positions, 81 numerology, and hexagram interpretation.

Project Architecture

The project uses a clean layered architecture: public types in core/, all implementation hidden in internal/, root package provides the only public API surface. External code can only import yi and yi/core — implementation details are fully encapsulated.

yi/
├── yi.go # Public API - re-exports types, provides all entry points
├── yi_test.go # Integration tests
├── doc.go # Package declaration
├── core/ # Public types, constants, errors, data stores
│ ├── types.go # Type definitions (Gua, Yao, ZhouYi, Bagua, WuXing, Sex, etc.)
│ ├── constants.go # Constants (Bagua, YaoPosition, WuXing, LiuQin, etc.)
│ ├── errors.go # Error definitions
│ ├── store.go # Data store declarations
│ └── data_gen.go # Auto-generated data initialization
├── internal/ # Implementation details (not importable externally)
│ ├── gua/ # Hexagram operations & transformations
│ ├── qigua/ # Divination methods (coins, dayan, meihua, time, lunar)
│ ├── jiegua/ # Hexagram interpretation & formatting
│ ├── wuxing/ # Five Elements operations
│ ├── jiazi/ # Sexagenary Cycle
│ ├── liuqin/ # Six Relations
│ ├── shiying/ # Shi-Ying positions
│ ├── numerology/ # 81 Numerology
│ ├── wenyan/ # Wenyan commentary
│ └── i18n/ # Internationalization (Chinese/English)
├── data/ # JSON data sources
├── cmd/
│ ├── divine/ # CLI tool
│ └── generate/ # Code generator
├── docs/ # Documentation
└── skills/ # AI Agent skills

Note: Import github.com/godcong/yi for the public API. Types are also available via github.com/godcong/yi/core. Implementation packages under internal/ are not importable by external code.

Daily Hexagram Skill

Recommended usage — Integrate with your AI assistant for daily divination.

User says "tell my fortune" → AI collects info → Generates full fortune report (800+ words)

Installation

npx skills add https://github.com/godcong/yi --skill daily-hexagram

After installation, the AI will automatically detect and download the yi binary for your platform on first use (via built-in SKILL.md rules).

Manual binary installation (optional)

If automatic installation fails, run the install script manually:

# macOS / Linux
./scripts/install.sh
# Windows (PowerShell)
.\scripts\install.bat

Or compile from source:

go install github.com/godcong/yi/cmd/divine@latest
# Then copy the compiled binary to the skill's bin/ directory

Compatible AI Agents

This Skill follows the Agent Skills open standard and works with all supporting AI agents:

Agent	Install Command
Claude Code	`npx skills add https://github.com/godcong/yi --skill daily-hexagram -a claude-code`
Trae	`npx skills add https://github.com/godcong/yi --skill daily-hexagram -a trae`
Cursor	`npx skills add https://github.com/godcong/yi --skill daily-hexagram -a cursor`
Codex	`npx skills add https://github.com/godcong/yi --skill daily-hexagram -a codex`
Goose	`npx skills add https://github.com/godcong/yi --skill daily-hexagram -a goose`
Gemini CLI	`npx skills add https://github.com/godcong/yi --skill daily-hexagram -a gemini-cli`
Roo Code	`npx skills add https://github.com/godcong/yi --skill daily-hexagram -a roo`
Windsurf	`npx skills add https://github.com/godcong/yi --skill daily-hexagram -a windsurf`
Others	Omit `-a` flag, interactively select target agent

See npx skills docs for the full list.

Usage

Simply talk to your AI assistant:

You say	What AI does
"tell my fortune", "daily horoscope"	Collects name + birthday → Daily hexagram (same person, same day = same hexagram)
"try another one"	Changes time and generates a new hexagram
"use coins"	Switches to coin method
"use yarrow stalks"	Switches to Dayan (yarrow) method
"plum blossom divination"	Switches to Meihua method

First use: AI will ask your name and birthday. After that, it remembers. Same person on the same day always gets the same hexagram.

Report Contents

Overview → Hexagram name / symbol / auspiciousness + core imagery + fortune基调
Details → Primary / transformed / moving lines / nuclear / inverse / reverse hexagrams
8-Dim Fortune → Career / Love / Wealth / Exams / Health / Travel / Lawsuit / Home
Do's & Don'ts → Today's recommended actions / taboos
Guidance → Action guidance + lucky direction / number / color

Full report is at least 800 words.

Supported Methods

Method	CLI	Description
Daily	`daily`	Date-based only, same person same day fixed
Time	`time`	Includes hour, different times yield different hexagrams
Coins	`coins`	Six coin tosses, most classic
Dayan	`dayan`	Yarrow stalk method, most ancient
Meihua	`meihua`	Plum blossom time-based
Number	`number`	Custom upper/lower trigram numbers

Skill Directory Structure

daily-hexagram/
├── SKILL.md # AI instructions (data-driven + AI interpretation)
├── bin/yi # Divination program (compiled binary)
├── references/
│ └── data-format.md # JSON output structure reference
├── scripts/
│ ├── install.sh # Install script
│ └── install.bat
└── user_profile.json # User info (auto-created)

CLI Tool

Installation

go install github.com/godcong/yi/cmd/divine@latest

Usage

# Daily hexagram (requires -seed for personalization)
yi -method daily -seed "John" -format json
# Time-based hexagram
yi -method time -seed "John" -sex male -format json
# Coin method
yi -method coins -coins-seed 42
# Plum blossom method
yi -method meihua -seed "John" -year 2026 -month 5 -day 12
# Dayan (yarrow) method
yi -method dayan -dayan-seed 999
# Number-based hexagram
yi -method number -ben 3 -bian 5 -dong 2

All Flags

Flag	Default	Description
`-method`	`time`	Method: `time` / `daily` / `coins` / `meihua` / `dayan` / `number`
`-seed`	`""`	User identifier (name/ID), required for `daily` and `time`
`-format`	`text`	Output format: `text` / `json`
`-lang`	`zh`	Output language: `zh` (Chinese) / `en` (English)
`-sex`	`male`	Gender: `male` / `female`
`-year`	current year	Gregorian year
`-month`	current month	Gregorian month
`-day`	current day	Gregorian day
`-hour`	current hour	Hour 0-23
`-coins-seed`	0	Coin method seed (0=random)
`-dayan-seed`	0	Dayan method seed
`-ben`	-1	Number method upper trigram (0-7)
`-bian`	-1	Number method lower trigram (0-7)
`-dong`	0	Number method moving line (0-5)
`-version`	—	Print version

Go Library

Installation

go get github.com/godcong/yi

Quick Start

package main
import (
"fmt""github.com/godcong/yi"
)
funcmain() {
// Daily hexagram (same person, same day = same hexagram)zy:=yi.DivineByDailyHexagram(2026, 5, 13, "John")
result:=yi.JieGua(zy, yi.Male)
fmt.Println(yi.FormatJieGua(result))
// Coin methodzy2, coins:=yi.DivineByCoins(42)
fmt.Printf("Primary: %s, Transformed: %s\n", zy2.GetGua(yi.Ben).Ming, zy2.GetGua(yi.Bian).Ming)
// Dayan (yarrow) methodzy3, _:=yi.DivineByDayan(999)
// Plum blossom methodzy4:=yi.DivineByMeihua(3, 5, 2)
// Time-based hexagramzy5:=yi.DivineByTimeGua(yi.TimeGuaParams{
Year: 2024, Month: 6, Day: 15, Hour: 10,
})
// Quick hex from current timezy6:=yi.DivineByCurrentTime()
_=zy6
}

Daily Hexagram Function

// Same person, same day = same hexagramzy:=yi.DivineByDailyHexagram(2026, 5, 13, "John")
result:=yi.JieGua(zy, yi.Male)
// result.JieDu contains pre-built 8-dimension fortune + do's/don'tsfmt.Println(result.JieDu.ShiYe) // Career fortunefmt.Println(result.JieDu.CoreImage) // Core imageryfmt.Println(result.JieDu.Yi) // Do'sfmt.Println(result.JieDu.Ji) // Don'ts// result.WuXingInfo contains Five Elements lucky attributesfmt.Println(result.WuXingInfo.LuckyNumber) // Lucky numberfmt.Println(result.WuXingInfo.LuckyColor) // Lucky color

API Overview

Divination Functions

Function	Description
`DivineByDailyHexagram(year, month, day int, personalSeed string) *ZhouYi`	Daily hexagram
`DivineByCurrentTime(personalSeed ...string) *ZhouYi`	Current time hexagram
`DivineByCoins(seed int64) (*ZhouYi, [6]CoinResult)`	Coin method
`DivineByDayan(seed int64) (*ZhouYi, [6]DayanResult)`	Dayan (yarrow) method
`DivineByMeihua(upperNum, lowerNum, dongYao int) *ZhouYi`	Plum blossom method
`DivineByMeihuaTime(t time.Time, seeds ...string) (*ZhouYi, int, int, int, int)`	Plum blossom time
`DivineByTimeGua(params TimeGuaParams, seed ...string) *ZhouYi`	Gregorian time
`DivineByTime(year, month, day, hour int, seed ...string) *ZhouYi`	Time-based divination
`DivineByLunarTime(lunarYear, lunarMonth, lunarDay, shichenNum int) *ZhouYi`	Lunar time
`DivineByNumber(shang, xia int, bianYao ...int) *ZhouYi`	Number-based
`Divine(shang, xia Bagua, bianYao ...int) *ZhouYi`	Trigram-based

Interpretation

Function	Description
`JieGua(zy ZhouYi, sex Sex) JieGuaResult`	Main interpretation function
`JieGuaWithLang(zy ZhouYi, sex Sex, lang Language) JieGuaResult`	Interpretation with language
`FormatJieGua(result *JieGuaResult) string`	Formatted output (Chinese)
`FormatJieGuaWithLang(result *JieGuaResult, lang Language) string`	Formatted output with language

Interpretation Result Structure

JieGuaResult contains:

Field	Description
`BenGuaInfo` / `BianGuaInfo`	Primary / Transformed hexagram {Ming, GuaName, Symbol, GuaYi, TuanText, XiangText, JiXiong, ...}
`HuGuaInfo` / `CuoGuaInfo` / `ZongGuaInfo`	Nuclear / Inverse / Reverse hexagrams
`DongYaoPos` / `DongYaoText` / `DongYaoJiXiong`	Moving line position / text / auspiciousness
`IsJi` / `JiXiongReason`	Overall auspiciousness / reason
`FenXi`	8-dimension interpretation [{Category, Content, JiXiong, Source}]
`JieDu`	Pre-built interpretation {CoreImage, ShiYe, AiQing, ..., Yi, Ji}
`WuXingInfo`	Five Elements lucky info {WuXing, Direction, LuckyNumber, LuckyColor}

Hexagram Lookup & Judgment

Function	Description
`GetGuaByIndex(index string) (*Gua, error)`	Lookup by index (e.g., "乾乾")
`GetGuaByXu(xu int) (*Gua, error)`	Lookup by sequence number (1-64)
`IsJi(zy *ZhouYi, sex Sex) bool`	Check auspiciousness (standalone function)
`FilterYao(zy *ZhouYi, sex Sex, filters ...string) bool`	Filter by auspiciousness
`GetShiYing(g Gua) ShiYingInfo`	Get Shi-Ying info (standalone function)
`GetGuaGong(g *Gua) Bagua`	Get palace attribution (standalone function)
`GetGuaPosition(g *Gua) GuaPosition`	Get hexagram position

Five Elements & Six Relations

Function	Description
`GetWuXingByBagua(bagua Bagua) WuXing`	Trigram → Five Elements
`GetLiuQin(guaGongWX, yaoWX WuXing) LiuQin`	Calculate Six Relations
`Sheng(wx WuXing) WuXing`	Generating relation
`Ke(wx WuXing) WuXing`	Overcoming relation
`BeiSheng(wx WuXing) WuXing`	Being generated
`BeiKe(wx WuXing) WuXing`	Being overcome

81 Numerology

Function	Description
`GetDayan(n int) (*Dayan, error)`	Lookup numerology (1-81)
`MustGetDayan(n int) Dayan`	Lookup numerology (panics on invalid)
`Dayan.IsJi()` / `.IsXiong()` / `.IsBest()`	Auspiciousness check

Wenyan Commentary

Function	Description
`GetWenYan(g Gua) WenYanData`	Get Wenyan commentary
`HasWenYan(g *Gua) bool`	Check if Wenyan exists

Internationalization

Function	Description
`JieGuaWithLang(zy, sex, lang)`	Interpretation with language
`FormatJieGuaWithLang(result, lang)`	Formatted output with language
`TranslateJiXiong(jx, lang)`	Translate auspiciousness
`TranslateCategory(cat, lang)`	Translate category
`TranslateYaoPos(pos, lang)`	Translate line position
`TranslateBaguaName(name, lang)`	Translate trigram name
`TranslateWuXing(name, lang)`	Translate Five Elements

Core Types

Type	Description
`Gua` (alias `Hexagram`)	Hexagram: name / meaning / Tuan / Xiang / six lines
`Yao` (alias `Line`)	Line: line text / auspiciousness / female fate
`ZhouYi` (alias `IChing`)	I Ching: five hexagram types + moving lines
`Bagua` (alias `Trigram`)	Eight Trigrams: 0=Qian...7=Kun
`WuXing`	Five Elements: Wood / Fire / Earth / Metal / Water
`Sex`	Gender: Male / Female
`LiuQin`	Six Relations: Parents / Siblings / Wealth / Offspring / Official
`Dayan`	Dayan numerology: 1-81 auspiciousness details
`JieGuaResult`	Interpretation result (includes JieDu + WuXingInfo)
`GuaJieDu`	Pre-built interpretation (8 dimensions + do's/don'ts)
`WuXingInfo`	Five Elements lucky attributes
`Language`	Output language: LangZH / LangEN

Hexagram Type Constants

Constant	Value	Description
`Ben`	0	Primary hexagram
`Bian`	1	Transformed hexagram
`Hu`	2	Nuclear hexagram (lines 2-3-4 lower, 3-4-5 upper)
`Cuo`	3	Inverse hexagram (all yin/yang flipped)
`Zong`	4	Reverse hexagram (upside down)

Eight Trigrams Constants

Constant	Value	WuXing	Name
`Qian`	0	Metal	Qian ☰ (Heaven)
`Dui`	1	Metal	Dui ☱ (Lake)
`Li`	2	Fire	Li ☲ (Fire)
`Zhen`	3	Wood	Zhen ☳ (Thunder)
`Xun`	4	Wood	Xun ☴ (Wind)
`Kan`	5	Water	Kan ☵ (Water)
`Gen`	6	Earth	Gen ☶ (Mountain)
`Kun`	7	Earth	Kun ☷ (Earth)

Convention: This project marks Yang as 0, Yin as 1 (bit representation), which is opposite to intuition.

Data Generation

Data is stored in JSON files under data/:

data/gua.json — 64 hexagrams
data/tuan.json — Tuan (Judgment) texts
data/xiang.json — Xiang (Image) texts
data/wenyan.json — Wenyan (Commentary) texts
data/jiazi.json — Sexagenary Cycle (60 JiaZi)
data/jiegua.json — Hexagram interpretations (8-dimension fortune + do's/don'ts + core imagery)
data/guagong.json — Palace attribution

Regenerate core/data_gen.go:

go run ./cmd/generate/

The generator reads JSON files from data/ and outputs core/data_gen.go.

Documentation

Introduction to Numerology — The numerical chain from Yin-Yang to 81 numerology
Divination Methods — Four divination methods explained
Eight Trigrams & 64 Hexagrams — Hexagram system and transformations
Dayan Numerology — 81 numerology auspiciousness
Six Relations & Shi-Ying — Six Relations system and Shi-Ying calculation

License

MIT License

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yi - I Ching (Book of Changes) Library for Go

Project Architecture

Daily Hexagram Skill

Installation

Compatible AI Agents

Usage

Report Contents

Supported Methods

Skill Directory Structure

CLI Tool

Installation

Usage

All Flags

Go Library

Installation

Quick Start

Daily Hexagram Function

API Overview

Divination Functions

Interpretation

Interpretation Result Structure

Hexagram Lookup & Judgment

Five Elements & Six Relations

81 Numerology

Wenyan Commentary

Internationalization

Core Types

Hexagram Type Constants

Eight Trigrams Constants

Data Generation

Documentation

License

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Name		Name	Last commit message	Last commit date
.github/workflows		.github/workflows
cmd		cmd
core		core
data		data
docs		docs
internal		internal
scripts		scripts
skills/daily-hexagram		skills/daily-hexagram
.gitignore		.gitignore
.goreleaser.yml		.goreleaser.yml
LICENSE		LICENSE
README.md		README.md
README_zh.md		README_zh.md
doc.go		doc.go
go.mod		go.mod
skills.json		skills.json
yi.go		yi.go
yi_test.go		yi_test.go

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yi - I Ching (Book of Changes) Library for Go

Project Architecture

Daily Hexagram Skill

Installation

Compatible AI Agents

Usage

Report Contents

Supported Methods

Skill Directory Structure

CLI Tool

Installation

Usage

All Flags

Go Library

Installation

Quick Start

Daily Hexagram Function

API Overview

Divination Functions

Interpretation

Interpretation Result Structure

Hexagram Lookup & Judgment

Five Elements & Six Relations

81 Numerology

Wenyan Commentary

Internationalization

Core Types

Hexagram Type Constants

Eight Trigrams Constants

Data Generation

Documentation

License

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