MareArts Computer Vision Study.

7/25/2025

Understanding C++ Templates, (class, member function and this)

template<int INT> 
  void AAA() {
      std::cout << "INT = " << INT << std::endl;
  }

  How to Call It:

  Normal Context (Outside Class):

  AAA<2>();           // ✅ Just call directly
  AAA<5>();           // ✅ Works fine
  AAA<10>();          // ✅ No problem

  Inside Template Class Context:

  template<typename T>
  class MyClass {
      template<int INT> 
      void AAA() {
          std::cout << "INT = " << INT << std::endl;
      }

      void some_function() {
          // WRONG:
          template AAA<2>();        // ❌ ERROR! Invalid syntax

          // CORRECT:
          this->template AAA<2>();  // ✅ Works!
          AAA<2>();                 // ✅ Usually works too
      }
  };

  Key Point:

  - template AAA<2>(); is INVALID C++ syntax
  - this->template AAA<2>(); is VALID C++ syntax

  The Rule:

  - template keyword only goes after -> or . in template contexts
  - You cannot start a statement with just template

  Correct Examples:

  this->template AAA<2>();      // ✅ In class context
  obj.template AAA<2>();        // ✅ With object
  ptr->template AAA<2>();       // ✅ With pointer
  AAA<2>();                     // ✅ Direct call (no template keyword needed)

C++ tuple vs vector, Tutorial

// ============================================================================
// SIMPLE COMPARISON: TUPLE vs VECTOR
// When to use which one and why they're different
// ============================================================================

#include <tuple>
#include <vector>
#include <iostream>
#include <string>

// ============================================================================
// VECTOR: Dynamic Array of SAME TYPE
// ============================================================================

void vector_example() {
    std::cout << "=== VECTOR EXAMPLE ===" << std::endl;
    
    // Vector holds multiple values of THE SAME TYPE
    std::vector<int> numbers = {10, 20, 30, 40, 50};
    
    std::cout << "Vector contents: ";
    for (size_t i = 0; i < numbers.size(); i++) {
        std::cout << numbers[i] << " ";
    }
    std::cout << std::endl;
    
    // Add more elements
    numbers.push_back(60);
    numbers.push_back(70);
    
    std::cout << "After adding elements: ";
    for (int num : numbers) {
        std::cout << num << " ";
    }
    std::cout << std::endl;
    
    std::cout << "Vector size: " << numbers.size() << std::endl;
    std::cout << "Can grow/shrink at runtime: YES" << std::endl;
    std::cout << "All elements same type: YES (int)" << std::endl;
}

// ============================================================================
// TUPLE: Fixed Collection of DIFFERENT TYPES
// ============================================================================

void tuple_example() {
    std::cout << "\n=== TUPLE EXAMPLE ===" << std::endl;
    
    // Tuple holds DIFFERENT TYPES in fixed positions
    std::tuple<int, float, std::string, bool> data = {42, 3.14f, "hello", true};
    
    std::cout << "Tuple contents:" << std::endl;
    std::cout << "Position 0 (int): " << std::get<0>(data) << std::endl;
    std::cout << "Position 1 (float): " << std::get<1>(data) << std::endl;
    std::cout << "Position 2 (string): " << std::get<2>(data) << std::endl;
    std::cout << "Position 3 (bool): " << std::get<3>(data) << std::endl;
    
    // Cannot add elements - size is fixed at compile time
    // data.push_back(something);  // ERROR! No such method
    
    std::cout << "Tuple size: " << std::tuple_size_v<decltype(data)> << std::endl;
    std::cout << "Can grow/shrink at runtime: NO" << std::endl;
    std::cout << "All elements same type: NO (int, float, string, bool)" << std::endl;
}

// ============================================================================
// SIDE-BY-SIDE COMPARISON
// ============================================================================

void comparison() {
    std::cout << "\n=== SIDE-BY-SIDE COMPARISON (marearts.com)===" << std::endl;
    
    // VECTOR: All same type, dynamic size
    std::vector<double> grades = {85.5, 92.0, 78.5, 95.0};
    
    // TUPLE: Different types, fixed size
    std::tuple<std::string, int, double, char> student = {"Alice", 20, 89.5, 'A'};
    
    std::cout << "VECTOR (grades):" << std::endl;
    std::cout << "  Type: vector<double>" << std::endl;
    std::cout << "  Values: ";
    for (double grade : grades) {
        std::cout << grade << " ";
    }
    std::cout << std::endl;
    std::cout << "  Access: grades[0], grades[1], grades[2]..." << std::endl;
    std::cout << "  Can add more: YES (grades.push_back(88.0))" << std::endl;
    
    std::cout << "\nTUPLE (student info):" << std::endl;
    std::cout << "  Type: tuple<string, int, double, char>" << std::endl;
    std::cout << "  Values: " << std::get<0>(student) << ", " 
              << std::get<1>(student) << ", " 
              << std::get<2>(student) << ", " 
              << std::get<3>(student) << std::endl;
    std::cout << "  Access: std::get<0>(student), std::get<1>(student)..." << std::endl;
    std::cout << "  Can add more: NO (fixed at compile time)" << std::endl;
}

// ============================================================================
// WHEN TO USE WHICH?
// ============================================================================

void when_to_use() {
    std::cout << "\n=== WHEN TO USE WHICH? ===" << std::endl;
    
    std::cout << "USE VECTOR WHEN:" << std::endl;
    std::cout << "  ✓ All elements are the same type" << std::endl;
    std::cout << "  ✓ You don't know size at compile time" << std::endl;
    std::cout << "  ✓ Size can change during runtime" << std::endl;
    std::cout << "  ✓ You want to loop through elements" << std::endl;
    std::cout << "  ✓ Examples: list of numbers, array of names, dynamic data" << std::endl;
    
    std::cout << "\nUSE TUPLE WHEN:" << std::endl;
    std::cout << "  ✓ Elements have different types" << std::endl;
    std::cout << "  ✓ Size is fixed and known at compile time" << std::endl;
    std::cout << "  ✓ Each position has specific meaning" << std::endl;
    std::cout << "  ✓ You want type safety for each element" << std::endl;
    std::cout << "  ✓ Examples: coordinates (x,y), person data (name,age,score), config settings" << std::endl;
}

// ============================================================================
// PRACTICAL EXAMPLES
// ============================================================================

void practical_examples() {
    std::cout << "\n=== PRACTICAL EXAMPLES ===" << std::endl;
    
    // VECTOR EXAMPLES (same type, dynamic)
    std::cout << "VECTOR use cases:" << std::endl;
    
    std::vector<int> test_scores;           // Dynamic list of test scores
    test_scores.push_back(85);
    test_scores.push_back(92);
    test_scores.push_back(78);              // Can keep adding
    
    std::vector<std::string> names = {"Alice", "Bob", "Charlie"};  // List of names
    
    std::cout << "  Test scores: ";
    for (int score : test_scores) std::cout << score << " ";
    std::cout << std::endl;
    
    // TUPLE EXAMPLES (different types, fixed)
    std::cout << "\nTUPLE use cases:" << std::endl;
    
    std::tuple<int, int> coordinates = {10, 20};                    // 2D point (x, y)
    std::tuple<std::string, int, char> student = {"Bob", 19, 'B'};  // Name, age, grade
    std::tuple<float, float, float> rgb_color = {0.8f, 0.2f, 0.5f}; // Red, green, blue
    
    auto [x, y] = coordinates;  // C++17 structured binding
    std::cout << "  Coordinates: (" << x << ", " << y << ")" << std::endl;
    std::cout << "  Student: " << std::get<0>(student) << ", age " << std::get<1>(student) 
              << ", grade " << std::get<2>(student) << std::endl;
}

// ============================================================================
// MEMORY AND PERFORMANCE
// ============================================================================

void memory_and_performance() {
    std::cout << "\n=== MEMORY & PERFORMANCE ===" << std::endl;
    
    // Vector - dynamic allocation
    std::vector<int> vec = {1, 2, 3, 4, 5};
    
    // Tuple - compile-time known, usually stack allocated
    std::tuple<int, int, int, int, int> tup = {1, 2, 3, 4, 5};
    
    std::cout << "VECTOR:" << std::endl;
    std::cout << "  Memory: Heap allocated (dynamic)" << std::endl;
    std::cout << "  Access: Runtime indexing vec[i]" << std::endl;
    std::cout << "  Size overhead: Stores capacity + size info" << std::endl;
    std::cout << "  Performance: Slight overhead for bounds checking" << std::endl;
    
    std::cout << "\nTUPLE:" << std::endl;
    std::cout << "  Memory: Usually stack allocated (compile-time size)" << std::endl;
    std::cout << "  Access: Compile-time indexing std::get<N>()" << std::endl;
    std::cout << "  Size overhead: None (just the data)" << std::endl;
    std::cout << "  Performance: Maximum efficiency (compile-time optimized)" << std::endl;
}

// ============================================================================
// CANNOT MIX - ERROR EXAMPLES
// ============================================================================

void error_examples() {
    std::cout << "\n=== WHAT YOU CANNOT DO ===" << std::endl;
    
    std::cout << "VECTOR limitations:" << std::endl;
    std::cout << "  ✗ Cannot mix types: vector<int, string> // COMPILER ERROR" << std::endl;
    std::cout << "  ✗ All elements must be same type" << std::endl;
    
    std::cout << "\nTUPLE limitations:" << std::endl;
    std::cout << "  ✗ Cannot resize: tuple.push_back() // NO SUCH METHOD" << std::endl;
    std::cout << "  ✗ Cannot loop easily (no iterators)" << std::endl;
    std::cout << "  ✗ Must know position at compile time: tuple[i] // ERROR" << std::endl;
    
    // Demonstrate what works
    std::vector<int> good_vector = {1, 2, 3};           // ✓ Same type
    // std::vector<int, string> bad_vector;             // ✗ COMPILER ERROR
    
    std::tuple<int, std::string> good_tuple = {42, "hello"};  // ✓ Different types
    // good_tuple.push_back(123);                       // ✗ NO SUCH METHOD
    
    std::cout << "\nWorking examples:" << std::endl;
    std::cout << "  Vector: " << good_vector[0] << ", " << good_vector[1] << std::endl;
    std::cout << "  Tuple: " << std::get<0>(good_tuple) << ", " << std::get<1>(good_tuple) << std::endl;
}

// ============================================================================
// MAIN FUNCTION
// ============================================================================

int main() {
    std::cout << "TUPLE vs VECTOR - Simple Comparison" << std::endl;
    std::cout << "====================================" << std::endl;
    
    vector_example();
    tuple_example();
    comparison();
    when_to_use();
    practical_examples();
    memory_and_performance();
    error_examples();
    
    std::cout << "\n=== QUICK SUMMARY ===" << std::endl;
    std::cout << "VECTOR = Same type + Dynamic size + Runtime flexibility" << std::endl;
    std::cout << "TUPLE  = Different types + Fixed size + Compile-time safety" << std::endl;
    std::cout << "\nThey solve different problems!" << std::endl;
    
    return 0;
}

// ============================================================================
// KEY DIFFERENCES SUMMARY:
// ============================================================================
//
// VECTOR<T>:
// - All elements type T (same type)
// - Dynamic size (can grow/shrink)
// - Runtime access: vec[i]
// - Memory: heap allocated
// - Use for: lists, arrays, collections
//
// TUPLE<T1, T2, T3>:
// - Each element different type
// - Fixed size (compile-time)
// - Compile-time access: std::get<N>()
// - Memory: usually stack
// - Use for: structured data, coordinates, configs
//
// CHOOSE BASED ON:
// - Same vs different types?
// - Dynamic vs fixed size?
// - Runtime vs compile-time access?

C++ Tuple Tutorial,

// ============================================================================
// COMPLETE C++ TUPLE TUTORIAL
// ============================================================================

#include <tuple>
#include <iostream>
#include <string>
#include <typeinfo>

// ============================================================================
// PART 1: BASIC TUPLE CONCEPTS
// ============================================================================

void basic_tuple_usage() {
    std::cout << "=== PART 1: Basic Tuple Usage ===" << std::endl;
    
    // Creating tuples with values
    std::tuple<int, float, std::string> data1 = {42, 3.14f, "hello"};
    std::tuple<int, float, std::string> data2(100, 2.5f, "world");
    auto data3 = std::make_tuple(200, 1.5f, "auto");
    
    // Accessing elements
    int first = std::get<0>(data1);        // Gets 42
    float second = std::get<1>(data1);     // Gets 3.14f
    std::string third = std::get<2>(data1); // Gets "hello"
    
    std::cout << "data1: " << first << ", " << second << ", " << third << std::endl;
    
    // Modifying elements
    std::get<0>(data1) = 999;
    std::cout << "Modified data1[0]: " << std::get<0>(data1) << std::endl;
    
    // Tuple size
    constexpr size_t size = std::tuple_size_v<decltype(data1)>;
    std::cout << "Tuple size: " << size << std::endl;
}

// ============================================================================
// PART 2: TUPLES WITH DIFFERENT SIZES
// ============================================================================

void different_tuple_sizes() {
    std::cout << "\n=== PART 2: Different Tuple Sizes ===" << std::endl;
    
    std::tuple<int> single = {10};                           // 1 element
    std::tuple<int, int> pair = {20, 30};                    // 2 elements
    std::tuple<int, int, int> triple = {40, 50, 60};         // 3 elements
    std::tuple<int, int, int, int, int> quintuple = {1, 2, 3, 4, 5}; // 5 elements
    
    std::cout << "Single: " << std::get<0>(single) << std::endl;
    std::cout << "Pair: " << std::get<0>(pair) << ", " << std::get<1>(pair) << std::endl;
    std::cout << "Triple: " << std::get<0>(triple) << ", " << std::get<1>(triple) << ", " << std::get<2>(triple) << std::endl;
    std::cout << "Quintuple[4]: " << std::get<4>(quintuple) << std::endl;
    
    // Tuple sizes
    std::cout << "Sizes: " << std::tuple_size_v<decltype(single)> << ", "
              << std::tuple_size_v<decltype(pair)> << ", "
              << std::tuple_size_v<decltype(triple)> << ", "
              << std::tuple_size_v<decltype(quintuple)> << std::endl;
}

// ============================================================================
// PART 3: MIXED TYPE TUPLES
// ============================================================================

void mixed_type_tuples() {
    std::cout << "\n=== PART 3: Mixed Type Tuples ===" << std::endl;
    
    // Different types in same tuple
    std::tuple<int, float, double, char, bool, std::string> mixed = {
        42, 3.14f, 2.718, 'A', true, "mixed"
    };
    
    std::cout << "Mixed tuple contents:" << std::endl;
    std::cout << "int: " << std::get<0>(mixed) << std::endl;
    std::cout << "float: " << std::get<1>(mixed) << std::endl;
    std::cout << "double: " << std::get<2>(mixed) << std::endl;
    std::cout << "char: " << std::get<3>(mixed) << std::endl;
    std::cout << "bool: " << std::get<4>(mixed) << std::endl;
    std::cout << "string: " << std::get<5>(mixed) << std::endl;
}

// ============================================================================
// PART 4: TUPLE_ELEMENT_T - EXTRACTING TYPES (NOT VALUES)
// ============================================================================

void tuple_element_type_extraction() {
    std::cout << "\n=== PART 4: Type Extraction with std::tuple_element_t ===" << std::endl;
    
    // Define a tuple TYPE (no actual values stored)
    using MyTupleType = std::tuple<int, float, double, std::string>;
    
    // Extract individual types from the tuple
    using FirstType = std::tuple_element_t<0, MyTupleType>;   // int
    using SecondType = std::tuple_element_t<1, MyTupleType>;  // float
    using ThirdType = std::tuple_element_t<2, MyTupleType>;   // double
    using FourthType = std::tuple_element_t<3, MyTupleType>;  // std::string
    
    // Use the extracted types to create variables
    FirstType var1 = 100;           // int var1 = 100;
    SecondType var2 = 2.5f;         // float var2 = 2.5f;
    ThirdType var3 = 3.14159;       // double var3 = 3.14159;
    FourthType var4 = "extracted";  // std::string var4 = "extracted";
    
    std::cout << "Variables created from extracted types:" << std::endl;
    std::cout << "var1 (int): " << var1 << std::endl;
    std::cout << "var2 (float): " << var2 << std::endl;
    std::cout << "var3 (double): " << var3 << std::endl;
    std::cout << "var4 (string): " << var4 << std::endl;
    
    // Show type information
    std::cout << "Type information:" << std::endl;
    std::cout << "FirstType: " << typeid(FirstType).name() << std::endl;
    std::cout << "SecondType: " << typeid(SecondType).name() << std::endl;
    std::cout << "ThirdType: " << typeid(ThirdType).name() << std::endl;
    std::cout << "FourthType: " << typeid(FourthType).name() << std::endl;
}

// ============================================================================
// PART 5: TUPLES IN TEMPLATES
// ============================================================================

template <typename TupleType>
class TupleProcessor {
    public:
    // Extract types from the tuple
    using FirstType = std::tuple_element_t<0, TupleType>;
    using SecondType = std::tuple_element_t<1, TupleType>;
    
    static constexpr size_t tuple_size = std::tuple_size_v<TupleType>;
    
    void process() {
        std::cout << "Processing tuple with " << tuple_size << " elements" << std::endl;
        
        // Create variables using extracted types
        FirstType first_var{};   // Default initialize
        SecondType second_var{};
        
        std::cout << "FirstType size: " << sizeof(FirstType) << " bytes" << std::endl;
        std::cout << "SecondType size: " << sizeof(SecondType) << " bytes" << std::endl;
    }
};

void tuples_in_templates() {
    std::cout << "\n=== PART 5: Tuples in Templates ===" << std::endl;
    
    // Different tuple types
    using IntFloatTuple = std::tuple<int, float>;
    using DoubleCharTuple = std::tuple<double, char>;
    using StringBoolTuple = std::tuple<std::string, bool>;
    
    // Create template instances with different tuple types
    TupleProcessor<IntFloatTuple> processor1;
    TupleProcessor<DoubleCharTuple> processor2;
    TupleProcessor<StringBoolTuple> processor3;
    
    processor1.process();
    processor2.process();
    processor3.process();
}

// ============================================================================
// PART 6: ADVANCED TUPLE TECHNIQUES
// ============================================================================

// Template that can handle tuples of any size
template <typename TupleType>
class FlexibleTupleHandler {
    public:
    static constexpr size_t size = std::tuple_size_v<TupleType>;
    
    // Always safe - every tuple has at least element 0
    using FirstType = std::tuple_element_t<0, TupleType>;
    
    // Conditional type extraction (C++17 feature)
    using SecondType = std::conditional_t<
        (size >= 2),
        std::tuple_element_t<1, TupleType>,
        void  // If tuple has less than 2 elements, use void
    >;
    
    void analyze_tuple() {
        std::cout << "Tuple analysis:" << std::endl;
        std::cout << "  Size: " << size << std::endl;
        std::cout << "  FirstType size: " << sizeof(FirstType) << " bytes" << std::endl;
        
        if constexpr (size >= 2) {
            std::cout << "  SecondType size: " << sizeof(SecondType) << " bytes" << std::endl;
        } else {
            std::cout << "  No second element" << std::endl;
        }
    }
};

void advanced_tuple_techniques() {
    std::cout << "\n=== PART 6: Advanced Tuple Techniques ===" << std::endl;
    
    // Test with different sized tuples
    FlexibleTupleHandler<std::tuple<int>> handler1;                    // 1 element
    FlexibleTupleHandler<std::tuple<int, float>> handler2;             // 2 elements
    FlexibleTupleHandler<std::tuple<int, float, double>> handler3;     // 3 elements
    
    handler1.analyze_tuple();
    handler2.analyze_tuple();
    handler3.analyze_tuple();
}

// ============================================================================
// PART 7: PRACTICAL EXAMPLE - TYPE-BASED CONFIGURATION
// ============================================================================

// Define some configuration "types" (like layouts in GPU programming)
struct FastConfig { static constexpr const char* name = "Fast"; };
struct SmallConfig { static constexpr const char* name = "Small"; };
struct PreciseConfig { static constexpr const char* name = "Precise"; };

template <typename ConfigTuple>
class ConfigurableProcessor {
    public:
    using DataType = std::tuple_element_t<0, ConfigTuple>;    // First: data type
    using SpeedConfig = std::tuple_element_t<1, ConfigTuple>; // Second: speed config
    using MemoryConfig = std::tuple_element_t<2, ConfigTuple>; // Third: memory config
    
    void run() {
        std::cout << "Running processor with:" << std::endl;
        std::cout << "  DataType size: " << sizeof(DataType) << " bytes" << std::endl;
        std::cout << "  Speed: " << SpeedConfig::name << std::endl;
        std::cout << "  Memory: " << MemoryConfig::name << std::endl;
    }
};

void practical_example() {
    std::cout << "\n=== PART 7: Practical Example ===" << std::endl;
    
    // Different configurations using tuples
    using Config1 = std::tuple<float, FastConfig, SmallConfig>;
    using Config2 = std::tuple<double, PreciseConfig, FastConfig>;
    using Config3 = std::tuple<int, SmallConfig, PreciseConfig>;
    
    ConfigurableProcessor<Config1> processor1;
    ConfigurableProcessor<Config2> processor2;
    ConfigurableProcessor<Config3> processor3;
    
    std::cout << "Configuration 1:" << std::endl;
    processor1.run();
    
    std::cout << "Configuration 2:" << std::endl;
    processor2.run();
    
    std::cout << "Configuration 3:" << std::endl;
    processor3.run();
}

// ============================================================================
// PART 8: TUPLE UNPACKING AND STRUCTURED BINDINGS (C++17)
// ============================================================================

void tuple_unpacking() {
    std::cout << "\n=== PART 8: Tuple Unpacking ===" << std::endl;
    
    std::tuple<int, float, std::string> data = {42, 3.14f, "hello"};
    
    // C++17 structured binding - unpack tuple into separate variables
    auto [number, decimal, text] = data;
    
    std::cout << "Unpacked values:" << std::endl;
    std::cout << "number: " << number << std::endl;
    std::cout << "decimal: " << decimal << std::endl;
    std::cout << "text: " << text << std::endl;
    
    // Modify unpacked variables (they're copies)
    number = 999;
    std::cout << "Modified number: " << number << std::endl;
    std::cout << "Original tuple[0]: " << std::get<0>(data) << std::endl;
}

// ============================================================================
// MAIN FUNCTION - RUN ALL EXAMPLES
// ============================================================================

int main() {
    std::cout << "C++ TUPLE COMPREHENSIVE TUTORIAL (MareArts)" << std::endl;
    std::cout << "=================================" << std::endl;
    
    basic_tuple_usage();
    different_tuple_sizes();
    mixed_type_tuples();
    tuple_element_type_extraction();
    tuples_in_templates();
    advanced_tuple_techniques();
    practical_example();
    tuple_unpacking();
    
    std::cout << "\n=== SUMMARY ===" << std::endl;
    std::cout << "1. Tuples can hold any number of elements (1, 2, 3, 5, 10...)" << std::endl;
    std::cout << "2. Tuples can store VALUES or define TYPES" << std::endl;
    std::cout << "3. std::get<N>(tuple) accesses values" << std::endl;
    std::cout << "4. std::tuple_element_t<N, TupleType> extracts types" << std::endl;
    std::cout << "5. Templates + tuples = powerful type-based programming" << std::endl;
    std::cout << "6. Perfect for configuration systems and generic programming" << std::endl;
    
    return 0;
}

// ============================================================================
// KEY TAKEAWAYS:
// ============================================================================
//
// 1. TUPLE BASICS:
//    - std::tuple<T1, T2, T3> can hold any types
//    - Access with std::get<0>(tuple), std::get<1>(tuple), etc.
//    - Size with std::tuple_size_v<TupleType>
//
// 2. TYPE EXTRACTION:
//    - std::tuple_element_t<N, TupleType> gets the Nth type
//    - Used at compile-time, not runtime
//    - Perfect for template programming
//
// 3. TEMPLATE USAGE:
//    - Tuples as template parameters enable type-based configuration
//    - One template + multiple tuple types = multiple specialized classes
//    - Compiler generates different code for each tuple type
//
// 4. FLEXIBILITY:
//    - Any tuple size works
//    - Mix any types in same tuple
//    - Conditional type extraction for varying sizes
//
// 5. PRACTICAL APPLICATIONS:
//    - Configuration systems (data type + algorithm choice)
//    - Generic programming (same code, different types)
//    - Type-safe parameter passing
//    - Template specialization without code duplication

7/09/2025

Claude Code install shell script

install Claude Code using this shell script

#!/bin/bash

# install-claude.sh
# Installs Node.js 18+, npm, and Claude Code CLI, handling common conflicts.

set -e

echo "=== [1/5] Removing conflicting Node.js and libnode-dev packages ==="
apt-get remove -y nodejs nodejs-doc libnode-dev || true

echo "=== [2/5] Cleaning up package manager ==="
apt-get autoremove -y
apt-get clean

echo "=== [3/5] Installing Node.js 18.x and npm ==="
curl -fsSL https://deb.nodesource.com/setup_18.x | bash -
apt-get install -y nodejs

# Ensure npm is installed (should be bundled with Node.js 18.x)
if ! command -v npm &>/dev/null; then
    echo "npm not found, installing..."
    apt-get install -y npm
fi

echo "=== [4/5] Verifying Node.js and npm installation ==="
node --version
npm --version

echo "=== [5/5] Installing Claude Code CLI ==="
npm install -g @anthropic-ai/claude-code

echo "=== Claude Code CLI installed successfully! ==="
echo "Run 'claude' to get started."

Thank you!

6/19/2025

Open Source License Commercial Use Guide

Understanding Commercial Rights in Open Source Licenses

📋 Legend

✅ Free: Commercial use is completely free without restrictions

⚠️ Conditional: Commercial use allowed with specific requirements

❌ Not Free: Commercial use prohibited or requires separate licensing

❓ Varies: Check specific license terms

💻 Traditional Software Licenses

Permissive Licenses (Business-Friendly)

License	Commercial Use	Key Requirements	Notes
Apache-2.0	✅ Free	Attribution, state changes, include license	Very permissive, patent grant included
MIT	✅ Free	Include copyright notice and license	One of the most permissive licenses
BSD-2-clause	✅ Free	Include copyright notice	Very permissive
BSD-3-clause	✅ Free	Include copyright notice, no endorsement	Slightly more restrictive than 2-clause
BSD-3-clause-clear	✅ Free	Same as BSD-3 but clarifies no patent rights	Patent rights explicitly not granted
ISC	✅ Free	Include copyright notice	Similar to MIT, very permissive
Unlicense	✅ Free	None - public domain dedication	No restrictions whatsoever
CC0-1.0	✅ Free	None - public domain dedication	Creative Commons "No Rights Reserved"
WTFPL	✅ Free	None	"Do What The F*** You Want" - no restrictions
Zlib	✅ Free	Don't misrepresent origin	Very permissive
PostgreSQL	✅ Free	Include copyright notice	Similar to MIT
BSL-1.0	✅ Free	Include license text if source distributed	Boost Software License - very permissive
PDDL	✅ Free	None - public domain	Public Domain Dedication License
NCSA	✅ Free	Include copyright and license	Similar to BSD/MIT

Copyleft Licenses (Conditional)

License	Commercial Use	Key Requirements	Notes
GPL-2.0/3.0	⚠️ Conditional	Must open source entire work	Strong copyleft - viral license
AGPL-3.0	⚠️ Conditional	Like GPL + network use = distribution	Strictest copyleft
LGPL-2.1/3.0	⚠️ Conditional	Share LGPL library mods, allow relinking	Lesser GPL - library-friendly
MPL-2.0	⚠️ Conditional	Share modifications of MPL code only	File-level copyleft
EPL-1.0/2.0	⚠️ Conditional	Share modifications, patent grant	Eclipse Public License
AFL-3.0	⚠️ Conditional	Attribution, share source if distributed	Academic Free License
OSL-3.0	⚠️ Conditional	Share source if distributed, attribution	Open Software License
ECL-2.0	⚠️ Conditional	Attribution, state changes	Educational Community License
MS-PL	⚠️ Conditional	Include license, share source if distributed	Microsoft Public License
EUPL-1.1/1.2	⚠️ Conditional	Share modifications	European Union Public License
Artistic-2.0	⚠️ Conditional	Attribution, share modifications	Perl's license
OFL-1.1	⚠️ Conditional	Keep font name, share modifications	Open Font License
GFDL	⚠️ Conditional	Include license, preserve sections	GNU Free Documentation License
LPPL-1.3c	⚠️ Conditional	Rename if modified	LaTeX Project Public License

🎨 Creative Commons Licenses

License	Commercial Use	Key Requirements	Notes
CC-BY-2.0/2.5/3.0/4.0	⚠️ Conditional	Attribution required	Creative Commons with attribution
CC-BY-SA-3.0/4.0	⚠️ Conditional	Attribution + share-alike	Must use same license for derivatives
CC-BY-ND-4.0	⚠️ Conditional	Attribution, no derivatives	Can't modify the work
CC-BY-NC-2.0/3.0/4.0	❌ Not Free	Non-commercial only	Commercial use prohibited
CC-BY-NC-SA-2.0/3.0/4.0	❌ Not Free	Non-commercial + share-alike	Commercial use prohibited
CC-BY-NC-ND-3.0/4.0	❌ Not Free	Non-commercial + no derivatives	Most restrictive CC license

🤖 AI Model Licenses

License	Commercial Use	Key Requirements	Notes
Llama2	⚠️ Conditional	Free up to 700M users, attribution	Meta's Llama 2 license
Llama3/3.1/3.2/3.3	⚠️ Conditional	Free up to 700M users, attribution	Updated Meta license
Llama4	⚠️ Conditional	Assumed similar to Llama3	Not yet released
Gemma	⚠️ Conditional	Prohibited uses list, attribution	Google's Gemma license
OpenRAIL	⚠️ Conditional	Use restrictions, attribution	Responsible AI License
OpenRAIL++	⚠️ Conditional	More restrictions than OpenRAIL	Enhanced responsible use
CreativeML-OpenRAIL-M	⚠️ Conditional	Use restrictions, attribution	For ML models
BigScience-OpenRAIL-M	⚠️ Conditional	Use restrictions, share license	BLOOM model license
BigScience-BLOOM-RAIL-1.0	⚠️ Conditional	Specific BLOOM restrictions	Original BLOOM license
BigCode-OpenRAIL-M	⚠️ Conditional	Code generation restrictions	For code models
DeepFloyd-IF-License	❌ Not Free	Research only by default	Commercial license needed
Apple-AMLA	⚠️ Conditional	Apple's specific terms	Apple Machine Learning
Apple-ASCL	⚠️ Conditional	Apple sample code terms	Limited to Apple platforms
Intel-Research	❌ Not Free	Research purposes only	Intel's research license

📊 Data Licenses

License	Commercial Use	Key Requirements	Notes
CDLA-Permissive-1.0/2.0	✅ Free	Attribution for data	Community Data License
CDLA-Sharing-1.0	⚠️ Conditional	Share data improvements	Copyleft for data
ODC-By	⚠️ Conditional	Attribution for databases	Open Data Commons
ODbL	⚠️ Conditional	Share-alike for databases	Open Database License
C-UDA	⚠️ Conditional	Computational use only	Computational Use of Data
Etalab-2.0	✅ Free	Attribution	French government open license

🔍 Generic/Other Licenses

License	Commercial Use	Key Requirements	Notes
Other	❓ Varies	Check specific license	Not a standard license
CC	❓ Varies	Depends on CC variant	Generic Creative Commons
BSD	✅ Free	Usually permissive	Generic BSD reference
GPL	⚠️ Conditional	Strong copyleft	Generic GPL reference
LGPL	⚠️ Conditional	Weak copyleft	Generic LGPL reference
LGPL-LR	⚠️ Conditional	LGPL with special exceptions	Language resources variant

⚠️ Important Notes

Always read the full license text - This guide provides general guidance but specific versions may have additional terms
"Conditional" means you CAN use commercially BUT must follow requirements - These aren't necessarily restrictive
Attribution is usually simple - Just credit the original authors/source
Copyleft/Share-alike - You must license derivatives under the same terms
Patent grants - Some licenses (Apache, EPL) explicitly grant patent rights
Compatibility - Not all licenses can be combined in one project
AI/ML licenses often have use-case restrictions - Even if commercial use is allowed, certain uses may be prohibited

🏆 Quick Reference Guide

Most Business-Friendly Licenses

MIT - Minimal requirements, maximum freedom
Apache-2.0 - Patent protection included
BSD variants - Simple and permissive
ISC - MIT-style simplicity
Unlicense - Public domain dedication
CC0-1.0 - No rights reserved

Decision Tree for Choosing a License

Want maximum freedom? → MIT or Apache-2.0
Building a library? → LGPL or MPL-2.0
Want improvements shared back? → GPL
Running a SaaS? → AGPL (if you want to enforce sharing)
Publishing content? → CC-BY (attribution only)
Using AI models? → Check user count limits carefully

Most Restrictive for Commercial Use

AGPL-3.0 - Requires source disclosure even for SaaS
CC-BY-NC-ND - No commercial use, no modifications
Research-only licenses - Intel-Research, DeepFloyd-IF
Any "NC" (non-commercial) license

💡 Pro Tips

For startups: Stick to MIT or Apache-2.0 for maximum flexibility
For open source projects: Consider your goals - permissive for adoption, copyleft for contributions
For using AI models: Always check the user/revenue thresholds
For content creators: CC-BY allows commercial use with attribution
For enterprises: Create an approved license list to streamline decisions

Last updated: June 2025

Disclaimer: This guide is for informational purposes only and does not constitute legal advice. Always consult with a legal professional for specific licensing questions.

6/18/2025

C++ Template Parameter Packs with sequence

C++ Template Parameter Packs with sequence

Simple Explanation

sequence<x,x,x> is a template that holds a compile-time list of integer values. It's like a

tuple but for numbers only, and the values are fixed at compile time. It's commonly used in

template metaprogramming to pass multiple integer parameters to other templates.

Simple Usage Example

#include <iostream>

  // A simple sequence template that holds compile-time integers

  template<int... Values>

  struct sequence {

      static constexpr int size = sizeof...(Values);

      // Function to print all values

      static void print() {

          ((std::cout << Values << " "), ...);  // C++17 fold expression

          std::cout << std::endl;

}

};

  // Template that uses sequence to create arrays

  template<typename T, int... Dims>

  class MultiArray {

  private:

      static constexpr int total_size = (Dims * ...);  // multiply all dimensions

      T data[total_size];

  public:

      MultiArray() {

          std::cout << "Created array with dimensions: ";

          ((std::cout << Dims << "x"), ...);

          std::cout << " = " << total_size << " elements" << std::endl;

}

      static constexpr int get_total_size() { return total_size; }

};

  int main() {

      // Create sequences with different values

      sequence<1, 8> block_warps;           // 1 block, 8 warps

      sequence<16, 16, 8> tensor_dims;      // 16x16x8 tensor

      sequence<2, 4, 8, 16> powers_of_2;    // sequence of powers

      std::cout << "Block warps: ";

      block_warps.print();  // Output: 1 8

      std::cout << "Tensor dims: ";

      tensor_dims.print();  // Output: 16 16 8

      std::cout << "Powers of 2: ";

      powers_of_2.print();  // Output: 2 4 8 16

      // Use sequence values as template parameters

      MultiArray<float, 10, 20> matrix2d;     // 10x20 = 200 elements

      MultiArray<int, 4, 4, 4> tensor3d;      // 4x4x4 = 64 elements

      return 0;

}

Output:

Block warps: 1 8

Tensor dims: 16 16 8

Powers of 2: 2 4 8 16

Created array with dimensions: 10x20x = 200 elements

Created array with dimensions: 4x4x4x = 64 elements

Thank you. 🙏

Pages

7/25/2025

Understanding C++ Templates, (class, member function and this)

C++ tuple vs vector, Tutorial

C++ Tuple Tutorial,

7/09/2025

Claude Code install shell script

6/19/2025

Open Source License Commercial Use Guide

Open Source License Commercial Use Guide

📋 Legend

💻 Traditional Software Licenses

Permissive Licenses (Business-Friendly)

Copyleft Licenses (Conditional)

🎨 Creative Commons Licenses

🤖 AI Model Licenses

📊 Data Licenses

🔍 Generic/Other Licenses

⚠️ Important Notes

🏆 Quick Reference Guide

Most Business-Friendly Licenses

Decision Tree for Choosing a License

Most Restrictive for Commercial Use

💡 Pro Tips

6/18/2025

C++ Template Parameter Packs with sequence