Grade Calculator

Build a grade calculation system with functions and lists

Exercise Overview

In this exercise, you’ll learn how to create a comprehensive grade management system that:

• Captures student grades from user input
• Calculates averages
• Identifies grades above the average
• Detects failing grades
• Manages multiple lists (movies, colors, etc.)

Exercise 1: Grade Analysis System

Problem Statement

Create a program that:

1. Capture 5 grades

   Ask the user to input 5 grades (decimal numbers)

2. Calculate average

   Compute the average of all grades

3. Find grades above average

   Display all grades that are greater than or equal to the average

4. Identify failing grades

   Display all grades below 6.0 (failing grades)

Solution Components

Function 1: Capture Grades

import 'dart:io';

List<double> capturarCalificaciones(List<double> calificaciones) {
  for (var i = 0; i < 5; i++) {
    print('Introducir un Valor doble:');
    calificaciones.add(double.parse(stdin.readLineSync()!));
  }
  return calificaciones;
}

This function uses double.parse() to convert string input to decimal numbers, allowing for grades like 8.5 or 9.75.

Function 2: Calculate Average

double calcularPromedio(List<double> calificaciones) {
  double suma = 0.0;
  for (var calificacion in calificaciones) {
    suma += calificacion;
  }
  return suma / calificaciones.length;
}

Understanding the average calculation

The function:

1. Initializes a sum variable to 0.0
2. Iterates through all grades, adding each to the sum
3. Divides the sum by the total number of grades
4. Returns the result as a double

Function 3: Display Grades Above Average

void imprimirMayoresPromedio(List<double> calificaciones, double promedio){
  for (var calificacion in calificaciones) {
    if (calificacion >= promedio) {
      print('La calificacion $calificacion es mayor o igual al Promedio');
    }
  }
}

Function 4: Display Failing Grades

void imprimirReprobatorias(List<double> calificaciones){
  for (var calificacion in calificaciones) {
    if (calificacion < 6.0) {
      print('La calificacion $calificacion es Reprobatoria');
    }
  }
}

In this system, any grade below 6.0 is considered failing. Make sure to adjust this threshold based on your grading system.

Complete Program

import 'dart:io';

List<double> capturarCalificaciones(List<double> calificaciones) {
  for (var i = 0; i < 5; i++) {
    print('Introducir un Valor doble:');
    calificaciones.add(double.parse(stdin.readLineSync()!));
  }
  return calificaciones;
}

double calcularPromedio(List<double> calificaciones) {
  double suma = 0.0;
  for (var calificacion in calificaciones) {
    suma += calificacion;
  }
  return suma / calificaciones.length;
}

void imprimirMayoresPromedio(List<double> calificaciones, double promedio){
  for (var calificacion in calificaciones) {
    if (calificacion >= promedio) {
      print('La calificacion $calificacion es mayor o igual al Promedio');
    }
  }
}

void imprimirReprobatorias(List<double> calificaciones){
  for (var calificacion in calificaciones) {
    if (calificacion < 6.0) {
      print('La calificacion $calificacion es Reprobatoria');
    }
  }
}

void main() {
  List<double> calificaciones = [];
  capturarCalificaciones(calificaciones);
  double promedio = calcularPromedio(calificaciones);
  imprimirMayoresPromedio(calificaciones, promedio);
  imprimirReprobatorias(calificaciones);
}

Exercise 2: Multiple List Management

Problem Statement

Create a program that manages two lists (movies and colors) and:

1. Load initial data

   Collect 5 items for each list from the user

2. Add more data

   Add one more item to each list

3. Display lists

   Print all items in a numbered format

4. Show list sizes

   Display the total count of items in each list

Solution Components

Reusable Function: Load List

import 'dart:io';

void cargarLista(List<String> lista, String mensaje){
  for (var i = 0; i < 5; i++) {
    print('Introducir tu $mensaje:');
    lista.add(stdin.readLineSync()!);
  }
}

By accepting a mensaje parameter, this function can be reused for any type of list, making the code more maintainable.

Reusable Function: Add Data

List<String> agregarDatos(List<String> lista, String mensaje) {
  print('\nAgregar $mensaje:');
  lista.add(stdin.readLineSync()!);
  return lista;
}

Reusable Function: Print Lists

void imprimirListas(List<String> lista, String mensaje) {
  print('\nListado de $mensaje:');
  for (var i = 0; i < lista.length; i++) {
    print('${i + 1} - ${lista[i]}');
  }
}

The list is printed with 1-based numbering (i + 1) to make it more user-friendly, even though list indices start at 0.

Reusable Function: Display Size

void tamanioListas(List<String> lista, String mensaje) {
  print('\nEl tamaño de la lista de $mensaje es: ${lista.length}');
}

Complete Program

import 'dart:io';

void cargarLista(List<String> lista, String mensaje){
  for (var i = 0; i < 5; i++) {
    print('Introducir tu $mensaje:');
    lista.add(stdin.readLineSync()!);
  }
}

List<String> agregarDatos(List<String> lista, String mensaje) {
  print('\nAgregar $mensaje:');
  lista.add(stdin.readLineSync()!);
  return lista;
}

void imprimirListas(List<String> lista, String mensaje) {
  print('\nListado de $mensaje:');
  for (var i = 0; i < lista.length; i++) {
    print('${i + 1} - ${lista[i]}');
  }
}

void tamanioListas(List<String> lista, String mensaje) {
  print('\nEl tamaño de la lista de $mensaje es: ${lista.length}');
}

void main() {
  List<String> peliculas = [];
  List<String> colores = [];

  //Cargamos 5 datos en cada Lista
  cargarLista(peliculas, 'Pelicula');
  print('');
  cargarLista(colores, 'Color');

  //Añadir 1 elemento más a cada lista
  agregarDatos(peliculas, 'una Pelicula');
  agregarDatos(colores, 'un Color');

  //Imprimimos los elementos de lista de manera enumerada
  imprimirListas(peliculas, 'Peliculas');
  imprimirListas(colores, 'Colores');

  //Imprimir el Tamaño de cada Lista
  tamanioListas(peliculas, 'Peliculas');
  tamanioListas(colores, 'Colores');
}

Key Concepts

List<double>

Used for storing decimal numbers like grades

List<String>

Used for storing text like movie names or colors

Reusable Functions

Functions with parameters can work with different data

Data Validation

Important to check for failing grades and other conditions

Practice Challenges

Challenge 1: Enhanced Statistics

Add functions to find:

• Highest grade
• Lowest grade
• Number of passing grades
• Percentage of students passing

Challenge 2: Grade Categories

Categorize grades into:

• Excellent (9.0-10.0)
• Good (8.0-8.9)
• Satisfactory (7.0-7.9)
• Passing (6.0-6.9)
• Failing (below 6.0)

Challenge 3: Combined Lists

Modify the movie/color program to:

• Allow the user to choose how many items to add initially
• Add a search function to find specific items
• Sort the lists alphabetically
• Remove items by index

Best Practices

Separation of Concerns

Each function should do one thing well

Meaningful Names

Use descriptive function and variable names

Input Validation

Always validate user input to prevent crashes

Code Reusability

Write functions that can be used in different contexts