A general-purpose functional programming language featuring dependent types, designed to bring type-dependent programming to mainstream software development.

Idris

Idris is a pure functional programming language that implements dependent types as a core feature, making it possible to express precise specifications directly in the type system while remaining practical for general-purpose programming.

Core Features

First-Class Types

Unlike many programming languages, Idris treats types as first-class citizens:

Types can be computed and manipulated like any other value
Functions can return types
Types can depend on runtime values

Totality Checking

Idris implements strong totality checking which ensures that:

Functions terminate for all inputs
Pattern matching is exhaustive
Recursive functions are structurally decreasing

Effects System

The language provides a powerful effects system that:

Tracks computational effects in types
Enables safe handling of side effects
Supports effect-dependent programming

Programming Paradigms

Dependent Type Programming

vAdd : Vect n Int -> Vect n Int -> Vect n Int
vAdd [] [] = []
vAdd (x :: xs) (y :: ys) = x + y :: vAdd xs ys

Type-Driven Development

Idris promotes a development workflow where:

Types are written first as specifications
Implementation follows from types
The compiler assists in program construction

Applications

Software Verification

Idris excels in creating verified software:

Protocol implementations
State machine modeling
Resource usage verification
Concurrent programming safety

Domain-Specific Languages

The powerful type system enables:

Safe embedded DSLs
Verified domain models
Type-safe metaprogramming

Comparison with Other Languages

Relative to Agda

More focused on practical programming
Enhanced IDE support
Lighter weight theorem proving

Relative to Haskell

Dependent types vs type classes
Stricter evaluation semantics
More precise type-level guarantees

Tooling and Ecosystem

Development Environment

Interactive editing support
Hole-driven development
Type-directed search
Integrated documentation

Package Management

Built-in build system
Package repository
External dependency management

Challenges and Limitations

Learning curve for dependent type programming
Compilation performance
Smaller ecosystem compared to mainstream languages
Resource consumption of type checking

Future Directions

The language continues to evolve with focus on:

Improved compilation strategies
Enhanced IDE support
Better error messages
Integration with existing systems
Applications in formal verification

Impact on Programming

Idris demonstrates how:

Type Theory can be practical
Program Verification can be accessible
Software Design can be type-driven

The language serves as a bridge between theoretical computer science and practical software development, influencing both research and industry practices.