A Declarative C++ Task Execution Library for Complex Workflows

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🔍 What is mr-contractor?
mr-contractor is a header-only C++ library that lets you declaratively define task execution graphs with seamless support for:

• Sequential & parallel stages
• Arbitrary nesting (parallel inside sequential, sequential inside parallel, etc.)
• Automatic dependency resolution
• Zero-boilerplate thread pooling

Built on latest C++ features, it’s perfect for scientific computing, game engines, or any domain requiring complex, repeatable workflows.

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🎯 Key Features

• Declarative API: Describe what your workflow does, not how to schedule it.
• Work Contracts: Underlying thread pool powered by work_contract for minimal overhead.
• Type Safety: Compile-time validation of task input/output types.

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🚀 Usage Examples

1. Simple Sequential Pipeline

auto task = Sequence{  
  [](int x) -> float { return x / 2.0f; },  
  [](float y) -> std::string { return std::to_string(y); }  
};  
auto result = apply(task, 42)->execute()->result();  
// result = "21.0"  

2. Parallel Processing

auto task = Parallel{  
  [](int a) { return a * a; },     // Task 1  
  [](int b) { return b + 10; }     // Task 2 (runs concurrently)  
};  
auto results = apply(task, std::tuple{2, 3})->execute()->result();  
// results = (4, 13)  

3. Nested Workflows

auto task = Sequence{  
  [](int x) { return std::tuple{x, x*2}; },  
  Parallel{  
    Sequence{  // Nested sequential steps  
      [](int a) { return a + 1; },  
      [](int b) { return std::to_string(b); }  
    },  
    [](int c) { return c * 0.5f; }  
  },  
  [](auto&& inputs) {  
    auto&& [str, flt] = inputs;  
    return str + " @ " + std::to_string(flt);  
  }  
};  
auto result = apply(task, 5)->execute()->result();  
// result = "6 @ 5.0"  

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Download the library

• via CPM.cmake in your CMake script (suggested):

  CPMAddPackage("gh:4J-company/mr-contractor#master")
  target_link_libraries(<your-project> PUBLIC mr-contractor-lib)

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We’d Love Your Feedback!

• Found a bug? Open an issue!
• Have a feature request? Let’s discuss!
• Built something cool with it? Share your story!