Refactoring Kind's switch with ChatSH

(This is a readable version of my ChatSH session. For the full log, click here.)

Taelin: Hello. We're going to refactor an aspect of the implementation of the Kind language. Are you ready? Start by doing 'ls', then 'cat kind-lang.cabal' to get familiar with the repo.

ChatSH: Certainly! I'm ready to help you refactor an aspect of the Kind language implementation. Let's start by examining the repository structure and the contents of the Cabal file.

ls && echo "---" && cat kind-lang.cabal

Taelin: okay. now, please read the Kind.Type module

ChatSH: Certainly! Let's read the contents of the Kind.Type module.

cat src/Kind/Type.hs

Taelin: write a short 2-sentence summary about Kind lang.

ChatSH: Kind is a functional programming language with a powerful type system that includes features like dependent types, self types, and algebraic data types. It appears to be designed for advanced type-level programming and theorem proving, with a focus on expressive power and mathematical rigor.

Taelin: it has a focus on simplicity. now, read the Show module

ChatSH: I apologize for the mischaracterization. Thank you for the correction about Kind's focus on simplicity. Now, let's read the Show module as requested.

cat src/Kind/Show.hs

Taelin: based on that, can you show an example of how the Mat and Swi syntaxes work? how they differ?

ChatSH: Certainly! Based on the Show module, I can provide examples of how the Mat (Match) and Swi (Switch) syntaxes work and how they differ.

Mat (Match) syntax: Mat is used for pattern matching on constructors. It looks like this:

λ{ #Constructor1: expression1 #Constructor2: expression2 ... }

Example:

λ{ #Some: x #None: 0 }

This would match on an Option-like type, returning x if it's Some, or 0 if it's None.

Swi (Switch) syntax: Swi is used for numeric switching, particularly on U32 values. It has this structure:

switch name = value { 0: zero_case _: successor_case }: rest_of_expression

Example:

switch n = x { 0: 1 _: (+ n-1 1) }: (+ n 2)

This would check if x is 0, return 1 if it is, otherwise return n-1 + 1, and then add 2 to the result.

Key differences:

1. Mat is for pattern matching on constructors (like in algebraic data types), while Swi is specifically for numeric (U32) switching.
2. Mat can handle multiple arbitrary constructors, while Swi is binary (0 case and non-0 case).
3. Swi introduces new variables (like n-1 in the successor case), which Mat doesn't do.
4. Swi has a continuation expression after the cases (after the colon), while Mat doesn't.

These constructs serve different purposes in the language, with Mat being more general for algebraic data types and Swi being specialized for numeric conditions.

Taelin: almost correct, but note that match requires lambdas, so, your example would be λ{ #Some: λx x #None: 0} instead. other than that, you're right. sadly, the problem is that this isn't consistent: match is implemented as a splitting lambda (that needs to be applied to the scrutinee), and switch is implemented as a complete pattern-match expression, that includes the scrutinee inside it. our goal is to refactor the entire language so that the switch expression uses a splitting lambda too. it should be written as: 'λ{ 0: u32_zero_case _: λpred u32_succ_case }'. this will simplify the implementation, and make it more consistent with Mat. we will do it FILE by FILE. your goal is to FULLY OVERWRITE an existing file to apply the needed changes to perform this refactor, one by one. when doing so, always overwrite the existing file with the COMPLETE new file. NEVER leave placeholders. do you understand? is there any question you'd like to ask before we start?

ChatSH: Thank you for the correction and clarification. I understand the goal now. We're going to refactor the language to make the switch expression use a splitting lambda, similar to the match expression, for consistency and simplification. We'll do this file by file, completely overwriting each file with the necessary changes.

Before we start, I have a few questions to ensure I understand the task correctly:

1. Will we need to update the parser to handle the new switch syntax?
2. Should we update any error messages or comments related to the switch expression?
3. Are there any other constructs in the language that might be affected by this change?
4. Do we need to update any test files or documentation alongside the implementation files?
5. How should we handle backwards compatibility, if at all?

Once these questions are addressed, I'll be ready to start the refactoring process, overwriting each file completely with the updated code as we go through them.

Taelin: 1. yes, we will update everything, the stringifier, the parser, the checker, to the new SWI format. 2. yes, update whatever is affected by this change, although I'm not sure if errors are affected directly. 3. no, only SWI is being currently updated. leave everything else the same, and pay extra caution not to break anything. 4. no, there are no tests or updates yet. 5. no, this is a fresh new language so there is nothing to be backwars compatible with. do you have any additional question?

ChatSH: Thank you for addressing those questions. Your answers provide a clear direction for the refactoring process. I don't have any additional questions at this moment. I understand that we need to:

1. Update the parser, stringifier, and checker for the new SWI format.
2. Modify any related error messages or comments as necessary.
3. Focus solely on updating SWI, leaving all other constructs unchanged.
4. Be cautious not to break any existing functionality.
5. Not worry about backwards compatibility or updating tests/documentation.

I'm ready to start the refactoring process. Please let me know which file you'd like to begin with, and I'll provide a complete, updated version of that file with the necessary changes for the new SWI format.

Taelin: thank you. let's start overwritting the Type.hs file now.

ChatSH: Certainly. I'll provide an updated version of the Type.hs file with the necessary changes for the new SWI format. Here's the complete, updated file:

<CODE>

The main change in this file is the update to the Swi constructor in the Term data type. Instead of containing multiple fields for the switch expression, it now only contains a single Term field. This change reflects the new format where the switch expression is implemented as a splitting lambda.

The rest of the file remains unchanged, as it doesn't directly interact with the internal structure of the Swi constructor. This change lays the groundwork for updating the parser, stringifier, and checker in subsequent files.

Taelin: that looks incorrect to me. why do you have only one Term on the Swi constructor? since there are 2 cases, you need two terms: one for the zero case, and one for the succ case. also, do now include the (updated to use splitting lambda) comment. please, overwrite it again.

ChatSH: I apologize for the confusion. You're absolutely right, and I thank you for the correction. Let me provide the correct updated version of the Type.hs file:

<CODE>

In this corrected version, the Swi constructor in the Term data type now has two Term fields, one for the zero case and one for the successor case, as you correctly pointed out. I've also removed the comment about the splitting lambda. The rest of the file remains unchanged.

Taelin: looks good, thank you. now, let's update the Show file.

ChatSH: Certainly. I'll update the Show.hs file to reflect the changes in the Swi constructor and its new representation. Here's the complete, updated Show.hs file:

<CODE>

The main changes in this file are:

1. Updated the Swi case in the termShower function to reflect the new structure:

Swi zero succ ->
  let zero' = termShower small zero dep
      succ' = termShower small succ dep
  in concat ["λ{ 0: ", zero', " _: ", succ', " }"]

This change shows the Swi constructor as a lambda expression with two cases, matching the new structure we defined in the Type.hs file.

The rest of the file remains unchanged, as it doesn't directly interact with the internal structure of the Swi constructor. This update ensures that the Show module correctly displays the new Swi structure when printing terms.

Taelin: that's right, thank you. now, let's read the parser module.

ChatSH: Certainly. I'll read the parser module for you. Please provide the contents of the parser file, which is likely named Parse.hs or Kind.Parse.hs.

cat src/Kind/Parse.hs

Taelin: update it now. note that, to avoid parser ambiguity, you want to parse Swi before Mat, and you should include a try to backtrack until the "0" character is parsed (when we see 'λ{ 0: ...', that means it is a Swi and not a Mat). does that make sense? update the parser now.

ChatSH: Certainly. I understand your requirements. I'll update the Parse.hs file to implement the new Swi syntax, parse Swi before Mat, and include a try to backtrack until the "0" character is parsed. Here's the updated Parse.hs file:

<CODE>

The main changes in this file are:

1. Moved parseSwi before parseMat in the parseTerm function.
2. Updated the parseSwi function to parse the new syntax:

parseSwi = withSrc $ P.try $ do
  P.string "λ{"
  parseTrivia
  P.string "0:"
  zero <- parseTerm
  parseTrivia
  P.string "_:"
  succ <- parseTerm
  parseTrivia
  P.char '}'
  return $ Swi zero succ

3. Added a P.try to the parseSwi function to allow backtracking if it's not a Swi expression.

These changes should allow the parser to correctly handle the new Swi syntax while avoiding ambiguity with Mat expressions. The parser will now recognize λ{ 0: ... _: ... } as a Swi expression, and other lambda expressions starting with λ{ will be parsed as Mat expressions.

Taelin: looks ok, but the P.try should only cover the first lines, until "0:" is parsed. after "0", it should be outside of the "try" block. also, do not add explanatory comments like "-- Moved before parseMat". this is valid from now on. overwrite the parser again.

ChatSH: Understood. I'll update the Parse.hs file according to your instructions. Here's the updated version without explanatory comments:

<CODE>

This version of the Parse.hs file includes the changes you requested. The P.try in the parseSwi function now only covers the initial part of the parsing up to "0:". The rest of the parsing is outside the try block. I've also removed all explanatory comments as requested.

Taelin: thanks. now, read the Reduce module.

ChatSH: Certainly. I'll read the Reduce module for you. Please provide the contents of the Reduce.hs file.

cat src/Kind/Reduce.hs

Taelin: refactor it to the new SWI format. on the reducer, you must treat Swi exactly like Mat, handling it inside the 'app' reducer. keep the same logic of the current swi function, just adjust it to the new format.

ChatSH: Certainly. I'll refactor the Reduce.hs file to accommodate the new SWI format. Here's the updated version of the file:

<CODE>

The main changes in this refactored version are:

1. Updated the Swi constructor to take only two arguments (zero and succ) instead of five.
2. Moved the Swi reduction logic into the app function, similar to how Mat is handled.
3. Updated the swi function to work with the new Swi format.
4. Modified the normal, bind, and subst functions to work with the new Swi structure.

The core logic for handling Swi remains the same, but it's now treated more like a function that's applied to its argument, consistent with the new format.

Taelin: thank you. there are a few issues though: 1. I just noticed you're not overwritting the files. you should use a 'sh' block to overwrite the modules, not a 'haskell' code block. 2. constructor fields should have 3 letters, so, you should call it 'zer' and 'suc', not 'zero' and 'succ'. this will improve the indentation and alignment of the code. 3. for consistency, swi should receive first the cases and then the scrutinee, not the other way around. overwrite the reduce module now, with these changes in mind.

ChatSH: I apologize for the oversights. You're absolutely right, and I appreciate your attention to detail. I'll make the necessary changes and use a shell block to overwrite the Reduce.hs file. Here's the corrected version:

<CODE>

This updated version of the Reduce.hs file incorporates the following changes:

1. Uses a shell block to overwrite the file.
2. Changes the constructor field names from 'zero' and 'succ' to 'zer' and 'suc'.
3. Adjusts the order of arguments in the swi function to receive the cases first and then the scrutinee.

These changes should improve consistency and alignment in the code. The core logic remains the same, but the structure has been adjusted to match your requirements.

Taelin: thanks. now, let's read the checker module.

ChatSH: Certainly. I'll read the checker module for you. Here's the command to display the contents of the Check.hs file:

cat src/Kind/Check.hs

Please provide the output of this command so I can analyze the checker module.

Taelin: update it to the new Swi format. to make the new Swi checker, take inspiration from the Mat checker. the new Swi checker should work just like a Mat with two cases. the structure and logic should be the same. this is hard, so, pay extra attention and reason about it carefully. update the checker now.

ChatSH: Certainly. I'll update the Check.hs file to accommodate the new Swi format, basing its structure on the Mat checker. This is indeed a complex task, so I'll approach it carefully. Here's the updated Check.hs file:

<CODE>

The main changes in this updated version are:

1. Updated the Swi case in the infer function to handle the new format.
2. Added a new Swi case in the check function, structured similarly to the Mat case but tailored for U32 switching.

In the new Swi checker:

• We check if the type is a function type (All) with U32 as input.
• We treat the Swi as having two cases: "0" for zer and "_" for suc.
• For the "0" case, we check zer against the body type applied to 0.
• For the "_" case, we check suc against a function type that takes a U32 and returns the body type applied to (1 + n).

This structure mirrors the Mat checker while adapting to the specific needs of U32 switching. The logic ensures that the Swi construct is used correctly with U32 values and maintains type safety.

Taelin: this makes sense, but I think the Swi case is too contrived. there is no reason to create a list and use forM. instead, you can just check both cases directly in the do block, making it more concise. rewrite the file with that in mind.

ChatSH: You're absolutely right. I apologize for the unnecessary complexity. Let's simplify the Swi case in the check function. I'll rewrite the Check.hs file with a more concise and direct approach for the Swi case:

<CODE>

In this updated version, the Swi case in the check function has been simplified:

1. We directly check the zero case (zer) against the type body applied to 0.
2. We then check the successor case (suc) against a function type that takes a U32 and returns the type body applied to (1 + n).

This approach is more concise and easier to read, while still maintaining the necessary type checks for the Swi construct. The logic ensures that the Swi is used correctly with U32 values and maintains type safety, but without the unnecessary complexity of creating a list and using forM.

Taelin: ok, let's now read Equal

ChatSH: Certainly. I'll read the Equal.hs file for you. Here's the command to display its contents:

cat src/Kind/Equal.hs

Please provide the output of this command so I can analyze the Equal module.

Taelin: update it to the new Swi format

ChatSH: Certainly. I'll update the Equal.hs file to accommodate the new Swi format. Here's the updated version:

<CODE>

The main changes in this updated version are:

1. In the identical function, the Swi case has been updated to match the new format:

go (Swi aZer aSuc) (Swi bZer bSuc) dep = do
  iZer <- identical aZer bZer dep
  iSuc <- identical aSuc bSuc dep
  return (iZer && iSuc)

2. Similarly, in the similar function, the Swi case has been updated:

go (Swi aZer aSuc) (Swi bZer bSuc) dep = do
  eZer <- equal aZer bZer dep
  eSuc <- equal aSuc bSuc dep
  return (eZer && eSuc)

3. In the occur function, the Swi case has been simplified to match the new format:

go (Swi zer suc) dep =
  let o_zer = go zer dep
      o_suc = go suc dep
  in o_zer || o_suc

These changes ensure that the Equal module correctly handles the new Swi format, maintaining consistency with the updates made in other modules.

Taelin: thank you. now, let's do Compile.hs

ChatSH: Certainly. I'll read the Compile.hs file for you and then we can update it to accommodate the new Swi format. First, let's view the current contents of the file:

cat src/Kind/Compile.hs

Please provide the output of this command so I can analyze the Compile module and suggest the necessary changes.

Taelin: update it!

ChatSH: Certainly! I'll update the Compile.hs file to accommodate the new Swi format. Here's the updated version:

<CODE>

The main change in this updated version is in the termToJS function, specifically the Swi case:

Swi zer suc ->
  let zer' = termToJS zer dep
      suc' = termToJS suc dep
  in concat ["((x => x === 0 ? ", zer', " : ", suc', "(x - 1)))"]

This new implementation:

1. Takes the two cases zer and suc as arguments.
2. Compiles both cases to JavaScript.
3. Creates a lambda function that checks if the input is 0.
4. If the input is 0, it returns the result of the zer case.
5. If the input is not 0, it applies the suc case to x - 1.

This change reflects the new Swi format while maintaining the same functionality as before. The rest of the file remains unchanged, as it doesn't directly interact with the Swi constructor.

Taelin: looks perfect, thank you. let's now do API

ChatSH: Certainly! Let's update the API.hs file to accommodate the new Swi format. First, I'll show you the current contents of the file:

cat src/Kind/API.hs

Please provide the output of this command so I can analyze the API module and suggest the necessary changes.

Taelin: update it

ChatSH: The API.hs file doesn't require many changes for the new Swi format, as most of the logic is handled in other modules. However, we need to update the getDeps function to match the new Swi structure. Here's the updated API.hs file:

<CODE>

The main change in this file is in the getDeps function:

getDeps :: Term -> [String]
getDeps term = case term of
  ...
  Swi zer suc   -> getDeps zer ++ getDeps suc
  ...

This change reflects the new Swi structure, which now has only two cases (zero and successor) instead of the previous five fields. The rest of the file remains unchanged as it doesn't directly interact with the Swi constructor.