fix up the packaging, add an infer command

.gitignore

@@ -1,3 +1,11 @@
 node_modules/
 build/
-.vscode/
+.vscode/
+.yarn/*
+!.yarn/cache
+!.yarn/patches
+!.yarn/plugins
+!.yarn/releases
+!.yarn/sdks
+!.yarn/versions
+*.tgz

.yarnrc.yml

@@ -0,0 +1 @@
+nodeLinker: node-modules

README.md

@@ -8,8 +8,8 @@ In the checkout directory:
 
 ```bash
 yarn install
-yarn run build
-yarn run ski
+yarn build
+yarn ski
 ```
 
 ## Books

bin/ski.ts

@@ -5,20 +5,40 @@ import tkexport from 'terminal-kit';
 const { create } = rsexport;
 const { terminal } = tkexport;
 
-import { stepOnceImmediate, stepOnceSKI } from '../lib/evaluator/skiEvaluator.js';
-import { generateExpr, SKIExpression, prettyPrint as prettyPrintSKI } from '../lib/ski/expression.js';
-import { parseSKI } from '../lib/parser/ski.js';
-import { prettyPrintUntypedLambda, UntypedLambda } from '../lib/terms/lambda.js';
-import { parseLambda } from '../lib/parser/untyped.js';
-import { prettyPrintSystemF, SystemFTerm } from '../lib/terms/systemF.js';
-import { parseSystemF } from '../lib/parser/systemFTerm.js';
-import { eraseTypedLambda, prettyPrintTypedLambda, TypedLambda } from '../lib/types/typedLambda.js';
-import { parseTypedLambda } from '../lib/parser/typed.js';
-import { eraseSystemF, prettyPrintSystemFType } from '../lib/types/systemF.js';
-import { convertLambda } from '../lib/conversion/converter.js';
-import { typecheck as typecheckTyped } from '../lib/types/typedLambda.js';
-import { typecheck as typecheckSystemF } from '../lib/types/systemF.js';
-import { prettyPrintTy } from '../lib/types/types.ts';
+import {
+  // SKI evaluator
+  stepOnceImmediate,
+  stepOnceSKI,
+  // SKI expressions
+  generateExpr,
+  prettyPrintSKI,
+  type SKIExpression,
+  // Parsers
+  parseSKI,
+  parseLambda,
+  parseSystemF,
+  parseTypedLambda,
+  // Lambda terms
+  prettyPrintUntypedLambda,
+  type UntypedLambda,
+  // System F
+  prettyPrintSystemF,
+  type SystemFTerm,
+  // Typed Lambda
+  eraseTypedLambda,
+  prettyPrintTypedLambda,
+  type TypedLambda,
+  typecheckTyped,
+  // System F types
+  eraseSystemF,
+  prettyPrintSystemFType,
+  typecheckSystemF,
+  // Conversion
+  convertLambda,
+  // Types
+  prettyPrintTy,
+  inferType
+} from '../lib/index.js';
 
 enum Mode {
   SKI = 'SKI',
@@ -282,6 +302,25 @@ function processCommand(input: string): void {
           }
           break;
       }
+    }
+    else if (cmd === 'infer' || cmd === 'i') {
+      // This command infers the type for the current untyped Lambda expression.
+      if (currentMode !== Mode.Lambda) {
+        printYellow('Type inference is only available in Lambda mode.');
+      } else if (currentLambda === null) {
+        printRed('No current Lambda term available for type inference.');
+      } else {
+        try {
+          const [typed, inferredType] = inferType(currentLambda);
+          currentTypedLambda = typed;
+          // Switch to TypedLambda mode since we now have a typed term.
+          currentMode = Mode.TypedLambda;
+          printGreen('Inferred Typed Lambda term: ' + prettyPrintTypedLambda(currentTypedLambda));
+          printGreen('Inferred type: ' + prettyPrintTy(inferredType));
+        } catch (e) {
+          printRed('Type inference error: ' + String(e));
+        }
+      }
     } else {
       printYellow('unknown command: ' + input);
     }
@@ -297,13 +336,12 @@ Available commands:
   :mode [ski|lambda|typed|systemf]  -- switch mode
   :help                             -- display this help message
   :quit                             -- exit the REPL
-Evaluation commands (in SKI mode):
-  :s or :step         -- step once (converts to SKI if necessary)
-  :m or :stepmany     -- step many (max 100 iterations, in SKI mode)
-  :g or :generate     -- generate a new SKI expression (SKI mode only)
-  :p or :print        -- print the current term
-Typechecking commands:
-  :tc or :typecheck   -- typecheck the current term (only available in TypedLambda and SystemF modes)
+  :s or :step                       -- step once (converts to SKI if necessary)
+  :m or :stepmany                   -- step many (max 100 iterations, in SKI mode)
+  :g or :generate                   -- generate a new SKI expression (SKI mode only)
+  :p or :print                      -- print the current term
+  :tc or :typecheck                 -- typecheck the current term (only available in TypedLambda and SystemF modes)
+  :infer or :i                      -- infer the type for the current untyped Lambda term and switch to TypedLambda mode
 
 Any other input is interpreted as a new term for the current mode.
 Press CTRL+C or type :quit to exit.`);

lib/consts/combinators.ts

@@ -1,6 +1,6 @@
-import { parseSKI } from '../parser/ski.ts';
-import { apply } from '../ski/expression.ts';
-import { K, I, S } from '../ski/terminal.ts';
+import { parseSKI } from '../parser/ski.js';
+import { apply } from '../ski/expression.js';
+import { S, K, I } from '../ski/terminal.js';
 
 /*
  * Zero. apply a function to its arguments zero times.

lib/consts/lambdas.ts

@@ -1,3 +1,3 @@
-import { parseLambda } from '../parser/untyped.ts';
+import { parseLambda } from '../parser/untyped.js';
 
 export const [, predLambda] = parseLambda('λn.λf.λx.n(λg.λh.h(gf))(λu.x)(λu.u)');

lib/conversion/converter.ts

@@ -1,9 +1,9 @@
-import { ConsCell, cons } from '../cons.ts';
-import { C, B } from '../consts/combinators.ts';
-import { LambdaVar, UntypedLambda } from '../terms/lambda.ts';
-import { SKIExpression } from '../ski/expression.ts';
-import { S, K, I, SKITerminal } from '../ski/terminal.ts';
-import { ConversionError } from './conversionError.ts';
+import { ConsCell, cons } from '../cons.js';
+import { C, B } from '../consts/combinators.js';
+import { LambdaVar, UntypedLambda } from '../terms/lambda.js';
+import { SKIExpression } from '../ski/expression.js';
+import { S, K, I, SKITerminal } from '../ski/terminal.js';
+import { ConversionError } from './conversionError.js';
 
 /**
  * Internal mixed-domain lambda abstraction.

lib/evaluator/skiEvaluator.ts

@@ -1,6 +1,6 @@
-import { cons, ConsCell } from '../cons.ts';
-import { prettyPrint, SKIExpression } from '../ski/expression.ts';
-import { SKITerminalSymbol } from '../ski/terminal.ts';
+import { cons, ConsCell } from '../cons.js';
+import { prettyPrint, SKIExpression } from '../ski/expression.js';
+import { SKITerminalSymbol } from '../ski/terminal.js';
 
 /**
   * the shape of an evaluation result.

lib/index.ts

@@ -0,0 +1,49 @@
+// Core evaluator exports
+export { stepOnceImmediate, stepOnceSKI } from './evaluator/skiEvaluator.js';
+
+// SKI expression exports
+export {
+  generateExpr,
+  prettyPrint as prettyPrintSKI,
+  type SKIExpression
+} from './ski/expression.js';
+
+// Parser exports
+export { parseSKI } from './parser/ski.js';
+export { parseLambda } from './parser/untyped.js';
+export { parseSystemF } from './parser/systemFTerm.js';
+export { parseTypedLambda } from './parser/typed.js';
+
+// Lambda terms exports
+export {
+  prettyPrintUntypedLambda,
+  type UntypedLambda
+} from './terms/lambda.js';
+
+// System F exports
+export {
+  prettyPrintSystemF,
+  type SystemFTerm
+} from './terms/systemF.js';
+
+// Typed Lambda exports
+export {
+  eraseTypedLambda,
+  prettyPrintTypedLambda,
+  type TypedLambda,
+  typecheck as typecheckTyped
+} from './types/typedLambda.js';
+
+// System F type exports
+export {
+  eraseSystemF,
+  prettyPrintSystemFType,
+  typecheck as typecheckSystemF
+} from './types/systemF.js';
+
+// Conversion exports
+export { convertLambda } from './conversion/converter.js';
+
+// Type system exports
+export { prettyPrintTy } from './types/types.js';
+export { inferType } from './types/inference.js';

lib/parser/chain.ts

@@ -1,6 +1,6 @@
-import { cons } from '../cons.ts';
-import { ParseError } from './parseError.ts';
-import { RecursiveDescentBuffer } from './recursiveDescentBuffer.ts';
+import { cons } from '../cons.js';
+import { ParseError } from './parseError.js';
+import { RecursiveDescentBuffer } from './recursiveDescentBuffer.js';
 
 export function parseLambdaChain<T>(
   rdb: RecursiveDescentBuffer,

lib/parser/eof.ts

@@ -1,5 +1,5 @@
-import { RecursiveDescentBuffer } from './recursiveDescentBuffer.ts';
-import { ParseError } from './parseError.ts';
+import { RecursiveDescentBuffer } from './recursiveDescentBuffer.js';
+import { ParseError } from './parseError.js';
 
 /**
  * Wraps a parser function so that after parsing the input,

lib/parser/recursiveDescentBuffer.ts

@@ -1,4 +1,4 @@
-import { ParseError } from './parseError.ts';
+import { ParseError } from './parseError.js';
 
 export class RecursiveDescentBuffer {
   buf!: string;

lib/parser/ski.ts

@@ -1,9 +1,9 @@
-import { SKIExpression } from '../ski/expression.ts';
-import { RecursiveDescentBuffer } from './recursiveDescentBuffer.ts';
-import { ParseError } from './parseError.ts';
-import { parseWithEOF } from './eof.ts';
-import { cons } from '../cons.ts';
-import { SKITerminalSymbol, term } from '../ski/terminal.ts';
+import { SKIExpression } from '../ski/expression.js';
+import { RecursiveDescentBuffer } from './recursiveDescentBuffer.js';
+import { ParseError } from './parseError.js';
+import { parseWithEOF } from './eof.js';
+import { cons } from '../cons.js';
+import { SKITerminalSymbol, term } from '../ski/terminal.js';
 
 /**
  * Parses a chain of SKI atomic terms (term { term }).

lib/parser/systemFTerm.ts

@@ -1,9 +1,9 @@
-import { cons } from '../cons.ts';
-import { SystemFTerm, mkSystemFAbs, mkSystemFTAbs, mkSystemFVar, mkSystemFTypeApp } from '../terms/systemF.ts';
-import { parseWithEOF } from './eof.ts';
-import { ParseError } from './parseError.ts';
-import { RecursiveDescentBuffer } from './recursiveDescentBuffer.ts';
-import { parseSystemFType } from './systemFType.ts';
+import { cons } from '../cons.js';
+import { SystemFTerm, mkSystemFAbs, mkSystemFTAbs, mkSystemFVar, mkSystemFTypeApp } from '../terms/systemF.js';
+import { parseWithEOF } from './eof.js';
+import { ParseError } from './parseError.js';
+import { RecursiveDescentBuffer } from './recursiveDescentBuffer.js';
+import { parseSystemFType } from './systemFType.js';
 
 /**
  * Parses an atomic System F term.

lib/parser/systemFType.ts

@@ -1,7 +1,7 @@
-import { SystemFType, forall } from '../types/systemF.ts';
-import { arrow, mkTypeVariable } from '../types/types.ts';
-import { ParseError } from './parseError.ts';
-import { RecursiveDescentBuffer } from './recursiveDescentBuffer.ts';
+import { SystemFType, forall } from '../types/systemF.js';
+import { arrow, mkTypeVariable } from '../types/types.js';
+import { ParseError } from './parseError.js';
+import { RecursiveDescentBuffer } from './recursiveDescentBuffer.js';
 
 /**
  * Parses a System F type.

lib/parser/type.ts

@@ -1,7 +1,7 @@
-import { RecursiveDescentBuffer } from './recursiveDescentBuffer.ts';
-import { ParseError } from './parseError.ts';
-import { BaseType, arrow, mkTypeVariable } from '../types/types.ts';
-import { parseWithEOF } from './eof.ts';
+import { RecursiveDescentBuffer } from './recursiveDescentBuffer.js';
+import { ParseError } from './parseError.js';
+import { BaseType, arrow, mkTypeVariable } from '../types/types.js';
+import { parseWithEOF } from './eof.js';
 
 /**
  * Parses a "simple" type.

lib/parser/typed.ts

@@ -1,9 +1,9 @@
-import { mkVar } from '../terms/lambda.ts';
-import { TypedLambda, mkTypedAbs } from '../types/typedLambda.ts';
-import { RecursiveDescentBuffer } from './recursiveDescentBuffer.ts';
-import { parseLambdaChain } from './chain.ts';
-import { parseArrowType } from './type.ts';
-import { parseWithEOF } from './eof.ts';
+import { mkVar } from '../terms/lambda.js';
+import { TypedLambda, mkTypedAbs } from '../types/typedLambda.js';
+import { RecursiveDescentBuffer } from './recursiveDescentBuffer.js';
+import { parseLambdaChain } from './chain.js';
+import { parseArrowType } from './type.js';
+import { parseWithEOF } from './eof.js';
 
 function parseAtomicTypedLambda(
   rdb: RecursiveDescentBuffer

lib/parser/untyped.ts

@@ -1,7 +1,7 @@
-import { UntypedLambda, mkUntypedAbs, mkVar } from '../terms/lambda.ts';
-import { RecursiveDescentBuffer } from './recursiveDescentBuffer.ts';
-import { parseLambdaChain } from './chain.ts';
-import { parseWithEOF } from './eof.ts';
+import { UntypedLambda, mkUntypedAbs, mkVar } from '../terms/lambda.js';
+import { RecursiveDescentBuffer } from './recursiveDescentBuffer.js';
+import { parseLambdaChain } from './chain.js';
+import { parseWithEOF } from './eof.js';
 
 function parseUntypedLambdaInternal(
   rdb: RecursiveDescentBuffer

lib/ski/church.ts

@@ -1,7 +1,7 @@
-import { Zero, One, Succ, True, False } from '../consts/combinators.ts';
-import { apply, SKIExpression } from './expression.ts';
-import { SKITerminalSymbol } from './terminal.ts';
-import { reduceSKI } from '../evaluator/skiEvaluator.ts';
+import { Zero, One, Succ, True, False } from '../consts/combinators.js';
+import { apply, SKIExpression } from './expression.js';
+import { SKITerminalSymbol } from './terminal.js';
+import { reduceSKI } from '../evaluator/skiEvaluator.js';
 
 /**
  * @see https://en.wikipedia.org/wiki/Church_encoding

lib/ski/expression.ts

@@ -1,7 +1,8 @@
 import { RandomSeed } from 'random-seed';
-import { ConsCell, cons } from '../cons.ts';
-import { stepOnceSKI } from '../evaluator/skiEvaluator.ts';
-import { SKITerminal, generate } from './terminal.ts';
+
+import { ConsCell, cons } from '../cons.js';
+import { stepOnceSKI } from '../evaluator/skiEvaluator.js';
+import { SKITerminal, generate } from './terminal.js';
 
 /*
  * EBNF grammar:
@@ -153,4 +154,4 @@ SKIExpression => {
   }
 };
 
-export { reduceSKI } from '../evaluator/skiEvaluator.ts';
+export { reduceSKI } from '../evaluator/skiEvaluator.js';

lib/ski/packer.ts

@@ -1,6 +1,6 @@
-import { cons } from '../cons.ts';
-import { SKIExpression } from './expression.ts';
-import { SKITerminalSymbol, term } from './terminal.ts';
+import { cons } from '../cons.js';
+import { SKIExpression } from './expression.js';
+import { SKITerminalSymbol, term } from './terminal.js';
 
 export type SymbolHeap = (SKITerminalSymbol | undefined)[];
 

lib/terms/lambda.ts

@@ -1,4 +1,4 @@
-import { ConsCell, cons } from '../cons.ts';
+import { ConsCell, cons } from '../cons.js';
 
 /**
  * This is a single term variable with a name.

lib/terms/systemF.ts

@@ -1,5 +1,5 @@
-import { ConsCell } from '../cons.ts';
-import { SystemFType } from '../types/systemF.ts';
+import { ConsCell } from '../cons.js';
+import { SystemFType } from '../types/systemF.js';
 
 /**
  * A term variable.