Functions, Domains, Ranges, and Graphs

/**
 * Fintech Math Bootcamp · Lesson 002 of 120
 * Functions, Domains, Ranges, and Graphs
 * Module 01: Mathematical Language and Quantitative Reasoning
 *
 * Scenario: A payment fee calculator with a valid input range
 * Rule:     fee(x) = 1 + 0.02x, x ≥ 0
 *
 * Try it:   Does a negative amount automatically mean a negative fee?
 *
 * Lesson article: https://thefintechbuilder.com/financial-mathematics-statistics-and-data-foundations/mathematical-language-and-quantitative-reasoning/functions-domains-ranges-and-graphs/
 * Free course:    https://courses.thefintechbuilder.com
 * Synthetic teaching example, not financial advice or a production library.
 */

export function lesson002() {
  const fee = (amount: number): number => {
    if (!Number.isFinite(amount) || amount < 0)
      throw new Error("Invalid amount");
    return 1 + 0.02 * amount;
  };
  const result = fee(100);
  return result;
}

export const checkedResult = 3;

// Run this file directly: npx tsx lessons/01-mathematical-language-and-quantitative-reasoning/002-functions-domains-ranges-and-graphs.ts
if (process.argv[1] && import.meta.url.endsWith(process.argv[1].replace(/\\/g, "/").split("/").pop()!)) {
  console.log(JSON.stringify(lesson002(), null, 2));
}

"""
Fintech Math Bootcamp · Lesson 002 of 120
Functions, Domains, Ranges, and Graphs
Module 01: Mathematical Language and Quantitative Reasoning

Scenario: A payment fee calculator with a valid input range
Rule:     fee(x) = 1 + 0.02x, x ≥ 0

Try it:   Does a negative amount automatically mean a negative fee?

Lesson article: https://thefintechbuilder.com/financial-mathematics-statistics-and-data-foundations/mathematical-language-and-quantitative-reasoning/functions-domains-ranges-and-graphs/
Free course:    https://courses.thefintechbuilder.com
Synthetic teaching example, not financial advice or a production library.

Run it: python main.py
"""

import json
import math


def lesson002() -> float:
    def fee(amount: float) -> float:
        if not math.isfinite(amount) or amount < 0:
            raise ValueError("Invalid amount")
        return 1 + 0.02 * amount

    result = fee(100)
    return result


if __name__ == "__main__":
    print(json.dumps(lesson002(), indent=2))

/**
 * Fintech Math Bootcamp · Lesson 002 of 120
 * Functions, Domains, Ranges, and Graphs
 * Module 01: Mathematical Language and Quantitative Reasoning
 *
 * Scenario: A payment fee calculator with a valid input range
 * Rule:     fee(x) = 1 + 0.02x, x ≥ 0
 *
 * Try it:   Does a negative amount automatically mean a negative fee?
 *
 * Lesson article: https://thefintechbuilder.com/financial-mathematics-statistics-and-data-foundations/mathematical-language-and-quantitative-reasoning/functions-domains-ranges-and-graphs/
 * Free course:    https://courses.thefintechbuilder.com
 * Synthetic teaching example, not financial advice or a production library.
 *
 * Run it: javac Main.java && java Main
 */

import java.util.function.DoubleUnaryOperator;

public class Main {
    static double lesson002() {
        DoubleUnaryOperator fee = amount -> {
            if (!Double.isFinite(amount) || amount < 0)
                throw new IllegalArgumentException("Invalid amount");
            return 1 + 0.02 * amount;
        };
        double result = fee.applyAsDouble(100);
        return result;
    }

    public static void main(String[] args) {
        System.out.println(num(lesson002()));
    }

    // Formats a double the way JSON.stringify does: whole numbers without ".0", null for NaN or infinity.
    static String num(double x) {
        if (Double.isNaN(x) || Double.isInfinite(x)) return "null";
        if (x == Math.rint(x) && Math.abs(x) < 1e15) return String.valueOf((long) x);
        return String.valueOf(x);
    }
}

// Fintech Math Bootcamp · Lesson 002 of 120
// Functions, Domains, Ranges, and Graphs
// Module 01: Mathematical Language and Quantitative Reasoning
//
// Scenario: A payment fee calculator with a valid input range
// Rule:     fee(x) = 1 + 0.02x, x ≥ 0
//
// Try it:   Does a negative amount automatically mean a negative fee?
//
// Lesson article: https://thefintechbuilder.com/financial-mathematics-statistics-and-data-foundations/mathematical-language-and-quantitative-reasoning/functions-domains-ranges-and-graphs/
// Free course:    https://courses.thefintechbuilder.com
// Synthetic teaching example, not financial advice or a production library.
//
// Run it: go run main.go

package main

import (
	"encoding/json"
	"errors"
	"fmt"
	"math"
	"os"
)

func lesson002() (float64, error) {
	fee := func(amount float64) (float64, error) {
		if math.IsNaN(amount) || math.IsInf(amount, 0) || amount < 0 {
			return 0, errors.New("Invalid amount")
		}
		return 1 + 0.02*amount, nil
	}
	result, err := fee(100)
	if err != nil {
		return 0, err
	}
	return result, nil
}

func main() {
	result, err := lesson002()
	if err != nil {
		fmt.Fprintln(os.Stderr, "Error:", err)
		os.Exit(1)
	}
	printJSON(result)
}

// printJSON prints a value as JSON indented with two spaces, like JSON.stringify(value, null, 2).
func printJSON(value any) {
	out, err := json.MarshalIndent(value, "", "  ")
	if err != nil {
		panic(err)
	}
	fmt.Println(string(out))
}

/**
 * Fintech Math Bootcamp · Lesson 002 of 120
 * Functions, Domains, Ranges, and Graphs
 * Module 01: Mathematical Language and Quantitative Reasoning
 *
 * Scenario: A payment fee calculator with a valid input range
 * Rule:     fee(x) = 1 + 0.02x, x ≥ 0
 *
 * Try it:   Does a negative amount automatically mean a negative fee?
 *
 * Lesson article: https://thefintechbuilder.com/financial-mathematics-statistics-and-data-foundations/mathematical-language-and-quantitative-reasoning/functions-domains-ranges-and-graphs/
 * Free course:    https://courses.thefintechbuilder.com
 * Synthetic teaching example, not financial advice or a production library.
 *
 * Run it: g++ -std=c++17 -o main main.cpp && ./main
 */

#include <charconv>
#include <cmath>
#include <iostream>
#include <stdexcept>
#include <string>

// Formats a double the way JSON.stringify does: shortest round-trip form, null for NaN or infinity.
std::string num(double x) {
    if (!std::isfinite(x)) return "null";
    char buffer[32];
    auto [end, error] = std::to_chars(buffer, buffer + sizeof buffer, x);
    (void)error;
    return std::string(buffer, end);
}

double lesson002() {
    auto fee = [](double amount) -> double {
        if (!std::isfinite(amount) || amount < 0)
            throw std::invalid_argument("Invalid amount");
        return 1 + 0.02 * amount;
    };
    const double result = fee(100);
    return result;
}

int main() {
    std::cout << num(lesson002()) << "\n";
}

//! Fintech Math Bootcamp · Lesson 002 of 120
//! Functions, Domains, Ranges, and Graphs
//! Module 01: Mathematical Language and Quantitative Reasoning
//!
//! Scenario: A payment fee calculator with a valid input range
//! Rule:     fee(x) = 1 + 0.02x, x ≥ 0
//!
//! Try it:   Does a negative amount automatically mean a negative fee?
//!
//! Lesson article: https://thefintechbuilder.com/financial-mathematics-statistics-and-data-foundations/mathematical-language-and-quantitative-reasoning/functions-domains-ranges-and-graphs/
//! Free course:    https://courses.thefintechbuilder.com
//! Synthetic teaching example, not financial advice or a production library.
//!
//! Run it: rustc main.rs && ./main

fn lesson002() -> Result<f64, String> {
    let fee = |amount: f64| -> Result<f64, String> {
        if !amount.is_finite() || amount < 0.0 {
            return Err("Invalid amount".to_string());
        }
        Ok(1.0 + 0.02 * amount)
    };
    let result = fee(100.0)?;
    Ok(result)
}

fn main() {
    match lesson002() {
        Ok(result) => println!("{}", num(result)),
        Err(message) => {
            eprintln!("Error: {}", message);
            std::process::exit(1);
        }
    }
}

/// Formats a number the way JSON.stringify does: shortest round-trip form, null for NaN or infinity.
fn num(x: f64) -> String {
    if x.is_finite() {
        format!("{}", x)
    } else {
        "null".to_string()
    }
}

/**
 * Fintech Math Bootcamp · Lesson 002 of 120
 * Functions, Domains, Ranges, and Graphs
 * Module 01: Mathematical Language and Quantitative Reasoning
 *
 * Scenario: A payment fee calculator with a valid input range
 * Rule:     fee(x) = 1 + 0.02x, x ≥ 0
 *
 * Try it:   Does a negative amount automatically mean a negative fee?
 *
 * Lesson article: https://thefintechbuilder.com/financial-mathematics-statistics-and-data-foundations/mathematical-language-and-quantitative-reasoning/functions-domains-ranges-and-graphs/
 * Free course:    https://courses.thefintechbuilder.com
 * Synthetic teaching example, not financial advice or a production library.
 *
 * Run it: dotnet run  (inside a console project that holds this Program.cs)
 */

using System.Text.Json;

Console.WriteLine(JsonSerializer.Serialize(Lesson002()));

static double Lesson002()
{
    static double Fee(double amount)
    {
        if (!double.IsFinite(amount) || amount < 0)
            throw new ArgumentException("Invalid amount");
        return 1 + 0.02 * amount;
    }

    var result = Fee(100);
    return result;
}