Всем привет!
Я тут поразвлекался с четвёртой версией ChatGPT, выдав ей следующее задание:
> Please, write a short specification for a new functional programming
> language. The language should preserve the syntax and semantics of Refal
> language as much as possible, but every function declaration in it must be
> typed.
Результат получился довольно забавный, и мне захотелось им поделиться:
Title: TypedRefal - A Typed Functional Programming Language Based on Refal
1. Introduction
TypedRefal is a new functional programming language that aims to preserve
the syntax and semantics of the Refal language while introducing static
typing to function declarations. This document provides a brief
specification of the language, focusing on its syntax, semantics, and type
system.
2. Syntax
The syntax of TypedRefal is largely based on the Refal language, with some
modifications to accommodate the introduction of types. The basic elements
of the language are:
- Identifiers: Identifiers are used to represent variables, functions, and
types. They consist of alphanumeric characters and underscores, starting
with a letter or underscore.
- Constants: Constants are either integer or string literals.
- Expressions: Expressions are sequences of identifiers, constants, and
parentheses, representing function calls and data structures.
- Patterns: Patterns are used to define the input of functions and consist
of identifiers, constants, and parentheses.
- Results: Results are used to define the output of functions and consist
of expressions.
3. Function Declarations
Function declarations in TypedRefal have the following structure:
```
<Type> <FunctionName> {
<Pattern> ::= <Result>
...
}
```
- `<Type>`: The type of the function, which consists of input and output
types separated by an arrow (->). For example, `Int -> String` represents a
function that takes an integer as input and returns a string as output.
- `<FunctionName>`: The name of the function, which is an identifier.
- `<Pattern>`: The input pattern of the function, which is matched against
the input expression.
- `<Result>`: The result expression, which is returned when the input
pattern is matched.
4. Types
TypedRefal introduces a static type system to the Refal language. The basic
types in TypedRefal are:
- Int: Represents integer values.
- String: Represents string values.
- List<T>: Represents lists of elements of type T.
- Tuple<T1, T2, ...>: Represents tuples of elements of different types.
- Function<T1, T2>: Represents functions that take an input of type T1 and
return a value of type T2.
5. Type Inference
TypedRefal supports type inference, allowing the compiler to automatically
deduce the types of expressions and function arguments based on their
usage. This reduces the need for explicit type annotations in many cases.
6. Type Checking
TypedRefal performs static type checking at compile-time, ensuring that
functions are called with the correct argument types and that their return
values are used correctly. This helps catch potential errors early in the
development process and improves the safety and reliability of the code.
7. Conclusion
TypedRefal is a functional programming language that extends the Refal
language with a static type system, providing improved safety and
reliability while preserving the familiar syntax and semantics of Refal.
With its strong typing and type inference capabilities, TypedRefal is
well-suited for a wide range of functional programming tasks.
Мне показалось, что данная "спецификация" слишком уж кратка и поверхностна,
и я попросил ChatCPT прояснить некоторые моменты:
> Please specify the syntax and semantics for TypedRefal expressions,
> patterns and results. Also write some example programs in TypedRefal.
В итоге всё стало гораздо интереснее, хоть он и позабыл об анонсированной
стрелочке в типовых выражениях, а также сильно налажал в грамматике и
примерах :-)
8. Expressions
Expressions in TypedRefal are used to represent function calls, data
structures, and values. They consist of identifiers, constants, and
parentheses. The syntax for expressions is as follows:
```
<expression> ::= <identifier> | <constant> | <function_call> | <list>
|tuple>
function_call> ::= <identifier> <expression>*
list> ::= [<expression>*]
<tuple> ::=expression>, <expression>, ...)
```
9. Patterns
Patterns in TypedRefal are used to define the input of functions. They
consist of identifiers, constants, and parentheses. The syntax for patterns
is as follows:
```
<pattern> ::= <identifier> |constant> | <list_pattern> | <tuple_pattern>
<list_pattern> ::= [<pattern>*]
<tuple_pattern> ::= (<pattern>, <pattern>, ...)
```
10. Results
Results in TypedRefal are used to define the output of functions. They
consist of expressions. The syntax for results is as follows:
```
result> ::= <expression>
```
11. Example Programs
Here are some example programs written in TypedRefal:
1. Factorial function:
```TypedRefal
Int factorial(Int n) {
0 ::= 1
n ::= n * factorial(n - 1)
}
```
2. Fibonacci function:
```TypedRefal
Int fibonacci(Int n) {
0 ::= 0
1 ::= 1
n ::= fibonacci(n - 1) + fibonacci(n - 2)
}
```
3. Length of a list:
```TypedRefal
Int length(List<A> xs) {
[] ::= 0
[x : xs] ::= 1 + length(xs)
}
```
4. Map function:
```TypedRefal
List<B> map(Function<A, B> f, List<A> xs) {
[] ::= []
[x : xs] ::= [f(x) : map(f, xs)]
}
```
5. Concatenate two lists:
```TypedRefal
List<A> concat(List<A> xs, List<A> ys) {
[] ::= ys
[x : xs] ::= [x : concat(xs, ys)]
}
```
6. Zip two lists into a list of tuples:
```TypedRefal
List<Tuple<A, B>> zip(List<A> xs, List<B> ys) {
[] ::= []
[x : xs] [y : ys] ::= [(x, y) : zip(xs, ys)]
}
```
These examples demonstrate the syntax and semantics of TypedRefal
expressions, patterns, and results, as well as the use of the type system
to ensure correct function calls and data structures.
В общем, ждём GPT-5. Я почти уверен, что оно придумает нам такой Рефал, что
земля содрогнётся 😁
С уважением,
Сергей.
