Welcome to OStack Knowledge Sharing Community for programmer and developer-Open, Learning and Share
Welcome To Ask or Share your Answers For Others

Categories

0 votes
778 views
in Technique[技术] by (71.8m points)

haskell - Is there a language with constrainable types?

Is there a typed programming language where I can constrain types like the following two examples?

  1. A Probability is a floating point number with minimum value 0.0 and maximum value 1.0.

    type Probability subtype of float
    where
        max_value = 0.0
        min_value = 1.0
    
  2. A Discrete Probability Distribution is a map, where: the keys should all be the same type, the values are all Probabilities, and the sum of the values = 1.0.

    type DPD<K> subtype of map<K, Probability>
    where
        sum(values) = 1.0
    

As far as I understand, this is not possible with Haskell or Agda.

See Question&Answers more detail:os

与恶龙缠斗过久,自身亦成为恶龙;凝视深渊过久,深渊将回以凝视…
Welcome To Ask or Share your Answers For Others

1 Answer

0 votes
by (71.8m points)

What you want is called refinement types.

It's possible to define Probability in Agda: Prob.agda

The probability mass function type, with sum condition is defined at line 264.

There are languages with more direct refinement types than in Agda, for example ATS


与恶龙缠斗过久,自身亦成为恶龙;凝视深渊过久,深渊将回以凝视…
...