Two Ways to Track Who Owns What (UTXO vs. Accounts)

// main.go
// Same transfer, two worldviews.

// Bitcoin (UTXO): consume whole coins, produce new ones
// inputs:  [utxo_A (0.3 BTC), utxo_B (0.25 BTC)]   // total 0.55
// outputs: [to_bob (0.2 BTC), change_to_me (0.349)]  // 0.001 fee
// After: utxo_A and utxo_B cease to exist. Two new UTXOs appear.

// Ethereum (account): mutate balance slots directly
// state[0xMe]  = state[0xMe]  - 0.2 ETH - gas
// state[0xBob] = state[0xBob] + 0.2 ETH
// Two key-value updates, no coins.

package main

import "fmt"

type UTXO struct {
	ID    string
	Owner string
	BTC   float64
}

func main() {
	// --- UTXO model ---
	inputs := []UTXO{
		{"utxo_A", "me", 0.3},
		{"utxo_B", "me", 0.25},
	}
	sendAmt := 0.2
	fee := 0.001
	total := 0.0
	for _, u := range inputs {
		total += u.BTC
	}
	change := total - sendAmt - fee
	outputs := []UTXO{
		{"utxo_new1", "bob", sendAmt},
		{"utxo_new2", "me", change},
	}

	fmt.Println("=== Bitcoin (UTXO) ===")
	fmt.Print("Consumed: ")
	for i, u := range inputs {
		if i > 0 {
			fmt.Print(", ")
		}
		fmt.Printf("%s(%.3f BTC)", u.ID, u.BTC)
	}
	fmt.Println()
	fmt.Print("Created:  ")
	for i, u := range outputs {
		if i > 0 {
			fmt.Print(", ")
		}
		fmt.Printf("%s->%s(%.3f BTC)", u.ID, u.Owner, u.BTC)
	}
	fmt.Println()
	fmt.Printf("Fee: %.3f BTC\n", fee)

	// --- Account model ---
	state := map[string]float64{"0xMe": 1.0, "0xBob": 0.5}
	gas := 0.0003
	fmt.Println("\n=== Ethereum (Account) ===")
	fmt.Printf("Before: 0xMe=%.4f  0xBob=%.4f\n", state["0xMe"], state["0xBob"])
	state["0xMe"] -= sendAmt + gas
	state["0xBob"] += sendAmt
	fmt.Printf("After:  0xMe=%.4f  0xBob=%.4f\n", state["0xMe"], state["0xBob"])
}