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Food !

by Cyrille Martraire, based on the Kebab kata from Romeu Moura

Let’s talk about food, from the perspective of diet compatibilities & nutrition facts.

You have ingredients: salad, cheese, tomato, bread, ham, fish… that you can combine in order to make a delicious Panini.

Each ingredient can be described by its diet compatibilities: vegan, vegetarian, or pescetarian, whether it's organic or not, and it has its own nutrition facts : calories, fat, salt and carbohydrates amounts (and many more). T

here are additional food items like drinks and deserts which can help create a meal together with a panini.

We want to derive the diet compatibilities & nutrition facts of any kind of Panini and for any meal built from these ingredients and food items.

Initial exploration

Here are sample data:

  • Salad is vegan, vegetarian, and pescetarian. It’s organic. Its nutrition facts are fat:0, salt:0, calories: 50.
  • Cheese is not vegan, but is vegetarian and pescetarian. It’s not organic. Its nutrition facts are fat:80, salt:0, calories: 20000.
  • Bread is vegan, vegetarian, and pescetarian. It’s organic. Its nutrition facts are fat:2, salt:0.2, calories: 100000.
  • Ham is not vegan, not vegetarian, and not pescetarian. It’s not organic. Its nutrition facts are fat:150, salt:0.1, calories: 30000.
  1. Explore how to code the calculation of a panini with just 2 ingredients. You may do it test-first.
  2. Propose a refactoring towards a well-known design pattern.

The Monoid way

Monoids are a ‘set’ and an ‘operation’ with specific properties: closure of the operation on the set, associativity, and neutral element.

In practice, monoids enable an arithmetic style, à la Object + Object = Object.

  1. Ask for a demo with glasses of beer to understand the abstract idea in a concrete way. Or watch the beginning of a video of one my related talks: https://www.youtube.com/watch?v=J9UwWo2qifg
  2. Discuss common examples of monoids that you know already.
  3. Turn the food example into a monoid fashion, into this style of assertions: “assert C = A + B”

Resources:

Extend!

Now we want to go further (depending on the time you have and your audacity):

  • Express the nutrition numbers in percent of the weight
  • Calculate the diet compatibilities proportions & average nutrition facts over millions of various meals served over a year
  • Check if a meal is locally produced (all ingredient producers are located within 100 kms)
  • Add units for nutrition facts, and/or an accuracy, eg: "10g +/-0.5"
  • Given that the facts results are already calculated for millions of meals, how to fix the results when you find out one particular meal was wrong without recalculating it all?

How easily can you extend the design to cope with these changes? Discuss and compare to other approaches.

Don't hesitate to ping me https://twitter.com/cyriux for feedback or questions