REPL checkpoint

src/Debug.kt

@@ -0,0 +1,3 @@
+data object Debug {
+    val on: Boolean = true
+}

src/Main.kt

@@ -1,9 +1,98 @@
-fun main() {
-    for (i in 1..10) {
-        println("Hello, Kotlin Command Line Utility!")
-    }
+import better_parser.PrologParser
+import better_parser.SimpleReplParser
+import interpreter.SourceFileReader
+import prolog.Answer
+import prolog.Program
+import prolog.ast.logic.Fact
+import prolog.ast.logic.Rule
+import prolog.ast.terms.Atom
+import prolog.ast.terms.CompoundTerm
+import prolog.ast.terms.Variable
+import prolog.builtins.Conjunction
+
+fun help(): String {
+    println("Unknown command. Type 'h' for help.")
+    println("Commands:")
+    println("  ;   - find next solution")
+    println("  a   - abort")
+    println("  .   - end query")
+    println("  h   - help")
+    println("  exit - exit Prolog REPL")
+    return ""
 }
 
-fun testMe(): String {
-    return "Hello, Kotlin Command Line Utility!"
+fun say(message: String) {
+    println(message)
+}
+
+fun prompt(message: String): String {
+    print("$message ")
+    var input: String = readlnOrNull() ?: help()
+    while (input.isBlank()) {
+        input = readlnOrNull() ?: help()
+    }
+    return input
+}
+
+fun prettyResult(result: Answer): String {
+    result.fold(
+        onSuccess = {
+            val subs = result.getOrNull()!!
+            if (subs.isEmpty()) {
+                return "true."
+            }
+            return subs.entries.joinToString(", ") { "${it.key} = ${it.value}" }
+        },
+        onFailure = {
+            return "Failure: ${result.exceptionOrNull()!!}"
+        }
+    )
+}
+
+val knownCommands = setOf(";", "a", ".")
+
+fun main() {
+    SourceFileReader().readFile("tests/better_parser/resources/parent.pl")
+
+    val parser = SimpleReplParser(debug = false)
+
+    say("Prolog REPL. Type 'exit' to quit.")
+
+    while (true) {
+        val queryString = prompt("?-")
+
+        try {
+            val query = parser.parse(queryString)
+            val answers = query.satisfy(emptyMap())
+
+            if (answers.none()) {
+                say("false.")
+            } else {
+                val iterator = answers.iterator()
+
+                var previous = iterator.next()
+
+                while (iterator.hasNext()) {
+                    var command = prompt(prettyResult(previous))
+
+                    while (command !in knownCommands) {
+                        say("Unknown action: $command (h for help)")
+                        command = prompt("Action?")
+                    }
+
+                    when (command) {
+                        ";" -> previous = iterator.next()
+                        "a" -> break
+                        "." -> break
+                    }
+                }
+
+                say(prettyResult(previous))
+            }
+
+        } catch (e: Exception) {
+            println("Error: ${e.message}")
+        }
+    }
+
 }

src/better_parser/PrologParser.kt

@@ -0,0 +1,17 @@
+package better_parser
+
+import com.github.h0tk3y.betterParse.grammar.Grammar
+import com.github.h0tk3y.betterParse.grammar.parseToEnd
+import prolog.Program
+import prolog.ast.logic.Clause
+import prolog.ast.terms.Atom
+
+class PrologParser {
+    private val parser: Grammar<List<Clause>> = SimpleSourceParser() as Grammar<List<Clause>>
+
+    public fun parse(input: String) {
+        val clauses: List<Clause> = parser.parseToEnd(input)
+
+        Program.load(clauses)
+    }
+}

src/better_parser/PrologSourceParser.kt

@@ -0,0 +1,70 @@
+package better_parser
+
+import com.github.h0tk3y.betterParse.combinators.*
+import com.github.h0tk3y.betterParse.grammar.Grammar
+import com.github.h0tk3y.betterParse.lexer.literalToken
+import com.github.h0tk3y.betterParse.lexer.regexToken
+import com.github.h0tk3y.betterParse.parser.Parser
+import prolog.ast.logic.Fact
+import prolog.ast.arithmetic.Integer
+import prolog.ast.arithmetic.Float
+import prolog.ast.logic.Clause
+import prolog.ast.logic.LogicOperand
+import prolog.ast.logic.Rule
+import prolog.ast.terms.*
+import prolog.builtins.Conjunction
+import prolog.builtins.Disjunction
+
+class PrologSourceParser : Grammar<List<Clause>>() {
+    // Define the tokens
+    private val atom by regexToken("[a-z][a-zA-Z0-9_]*")
+    private val variable by regexToken("[A-Z][a-zA-Z0-9_]*")
+    private val number by regexToken("-?[0-9]+(\\.[0-9]+)?")
+    private val whitespace by regexToken("\\s+", ignore = true)
+
+    private val comma by literalToken(",")
+    private val semicolon by literalToken(";")
+    private val neck by literalToken(":-")
+    private val lparen by literalToken("(")
+    private val rparen by literalToken(")")
+    private val dot by literalToken(".")
+
+    private val atomParser by atom use { Atom(text) }
+    private val variableParser by variable use { Variable(text) }
+    private val intParser by number use { Integer(text.toInt()) }
+    private val floatParser by number use { Float(text.toFloat()) }
+    private val numberParser by (intParser or floatParser)
+    private val compoundTermParser by (atomParser and skip(lparen) and separated(
+        atomParser or variableParser,
+        comma
+    ) and skip(rparen)) use {
+        CompoundTerm(t1, t2.terms)
+    }
+
+    private val termParser: Parser<Term> by (numberParser or variableParser or compoundTermParser or atomParser)
+
+    private val logicOperandParser: Parser<LogicOperand> by (termParser or compoundTermParser or atomParser) map {
+        it as LogicOperand
+    }
+
+    private val conjunctionParser: Parser<Conjunction> by (logicOperandParser and comma and logicOperandParser) use {
+        Conjunction(t1, t3)
+    }
+    private val disjunctionParser: Parser<Disjunction> by (logicOperandParser and semicolon and logicOperandParser) use {
+        Disjunction(t1, t3)
+    }
+
+    private val operatorParser: Parser<Operator> by (conjunctionParser or disjunctionParser)
+
+    private val headParser by (compoundTermParser or atomParser)
+    private val bodyParser by (operatorParser or compoundTermParser or atomParser)
+
+    private val factParser by (headParser and dot) use { Fact(t1 as Head) }
+    private val ruleParser by (headParser and neck and bodyParser and dot) use {
+        Rule(t1 as Head, t3 as Body)
+    }
+
+    private val clauseParser: Parser<Clause> by (factParser or ruleParser)
+
+    override val rootParser: Parser<List<Clause>> by zeroOrMore(clauseParser)
+}

src/better_parser/SimplePrologParser.kt

@@ -6,6 +6,7 @@ import com.github.h0tk3y.betterParse.grammar.parser
 import com.github.h0tk3y.betterParse.lexer.Token
 import com.github.h0tk3y.betterParse.lexer.literalToken
 import com.github.h0tk3y.betterParse.lexer.regexToken
+import com.github.h0tk3y.betterParse.lexer.token
 import com.github.h0tk3y.betterParse.parser.Parser
 import prolog.ast.arithmetic.Float
 import prolog.ast.arithmetic.Integer
@@ -16,28 +17,32 @@ import prolog.ast.terms.Variable
 
 open class SimplePrologParser : Grammar<Any>() {
     // Prolog tokens
-    private val nameToken: Token by regexToken("[a-z][a-zA-Z0-9_]*")
-    private val variableToken: Token by regexToken("[A-Z][a-zA-Z0-9_]*")
+    protected val nameToken: Token by regexToken("[a-z][a-zA-Z0-9_]*")
+    protected val variableToken: Token by regexToken("[A-Z][a-zA-Z0-9_]*")
 
     // Arithmetic tokens
     private val floatToken: Token by regexToken("-?[1-9][0-9]*\\.[0-9]+")
     private val integerToken: Token by regexToken("-?([1-9][0-9]*|0)")
 
     // Special tokens
-    private val comma: Token by literalToken(",")
-    private val leftParenthesis: Token by literalToken("(")
-    private val rightParenthesis: Token by literalToken(")")
+    protected val neck by literalToken(":-")
+    protected val comma: Token by literalToken(",")
+    protected val leftParenthesis: Token by literalToken("(")
+    protected val rightParenthesis: Token by literalToken(")")
+    protected val dot by literalToken(".")
 
     // Ignored tokens
-    private val whitespace: Token by regexToken("\\s+", ignore = true)
-    private val singleLineComment: Token by regexToken("%[^\\n]*", ignore = true)
-    private val multiLineComment: Token by regexToken("/\\*.*?\\*/", ignore = true)
+    protected val whitespace: Token by regexToken("\\s+", ignore = true)
+    protected val singleLineComment: Token by regexToken("%[^\\n]*", ignore = true)
+    protected val multiLineComment: Token by regexToken("/\\*.*?\\*/", ignore = true)
+
+    protected val dummy by token { _, _ -> -1 } use { throw IllegalStateException("This parser should not be used") }
 
     // Prolog parsers
-    private val atomParser: Parser<Atom> by nameToken use { Atom(text) }
-    private val variableParser: Parser<Variable> by variableToken use { Variable(text) }
-    private val structureParser: Parser<Structure> by (atomParser and skip(leftParenthesis) and separated(
-        parser(this::termParser),
+    protected val variable: Parser<Variable> by variableToken use { Variable(text) }
+    protected val atom: Parser<Atom> by nameToken use { Atom(text) }
+    protected val compound: Parser<Structure> by (atom and skip(leftParenthesis) and separated(
+        parser(::term),
         comma,
         acceptZero = true
     ) and skip(rightParenthesis)) use {
@@ -45,17 +50,18 @@ open class SimplePrologParser : Grammar<Any>() {
     }
 
     // Arithmetic parsers
-    private val integerParser: Parser<Integer> by integerToken use { Integer(text.toInt()) }
-    private val floatParser: Parser<Float> by floatToken use {
+    private val int: Parser<Integer> by integerToken use { Integer(text.toInt()) }
+    private val float: Parser<Float> by floatToken use {
         Float(text.toFloat())
     }
 
-    private val termParser: Parser<Term> by (floatParser
-            or integerParser
-            or variableParser
-            or structureParser
-            or atomParser
+    protected val term: Parser<Term> by (dummy
+            or float
+            or int
+            or variable
+            or compound
+            or atom
     ) map { it }
 
-    override val rootParser: Parser<Any> = termParser
+    override val rootParser: Parser<Any> = term
 }

src/better_parser/SimpleReplParser.kt

@@ -0,0 +1,27 @@
+package better_parser
+
+import com.github.h0tk3y.betterParse.combinators.times
+import com.github.h0tk3y.betterParse.combinators.unaryMinus
+import com.github.h0tk3y.betterParse.combinators.use
+import com.github.h0tk3y.betterParse.grammar.parseToEnd
+import com.github.h0tk3y.betterParse.parser.Parser
+import prolog.ast.logic.LogicOperand
+import prolog.builtins.Query
+
+class SimpleReplParser(val debug: Boolean = false) : SimpleSourceParser() {
+    override val rootParser: Parser<Query> by (body * -dot) use { Query(this as LogicOperand) }
+
+    fun parse(input: String): Query {
+        if (debug) {
+            println("Parsing input: $input")
+        }
+
+        val query = parseToEnd(input) as Query
+
+        if (debug) {
+            println("Parsed query: $query")
+        }
+
+        return query
+    }
+}

src/better_parser/SimpleSourceParser.kt

@@ -0,0 +1,48 @@
+package better_parser
+
+import com.github.h0tk3y.betterParse.combinators.*
+import com.github.h0tk3y.betterParse.grammar.parser
+import com.github.h0tk3y.betterParse.lexer.literalToken
+import com.github.h0tk3y.betterParse.parser.Parser
+import prolog.ast.arithmetic.ArithmeticOperator
+import prolog.ast.logic.*
+import prolog.ast.terms.*
+import prolog.builtins.Conjunction
+import prolog.builtins.Disjunction
+
+open class SimpleSourceParser : SimplePrologParser() {
+    protected val simpleLogicOperand: Parser<LogicOperand> by (dummy
+            or compound
+            or atom
+            )
+    protected val logicOperand: Parser<LogicOperand> by (dummy
+        or parser(::operator)
+        or simpleLogicOperand
+    )
+
+    protected val arithmeticOperator: Parser<ArithmeticOperator> by dummy
+    protected val logicOperator: Parser<LogicOperator> by (simpleLogicOperand * comma * logicOperand) use {
+        Conjunction(t1, t3)
+    }
+
+    protected val operator: Parser<Operator> by (arithmeticOperator or logicOperator) use { this as Operator }
+
+    protected val head: Parser<Head> by (dummy
+            or compound
+            or atom
+            )
+    protected val body: Parser<Body> by (dummy
+            or operator
+            or head
+            ) use { this as Body }
+
+    // ----
+
+    private val rule: Parser<Rule> by (head * -neck * body) use { Rule(t1, t2) }
+    private val fact: Parser<Fact> by head use { Fact(this) }
+
+    private val clause: Parser<Clause> by ((rule or fact) * -dot)
+    private val clauses: Parser<List<Clause>> by zeroOrMore(clause)
+
+    override val rootParser: Parser<Any> by clauses
+}

src/interpreter/SourceFileReader.kt

@@ -0,0 +1,23 @@
+package interpreter
+
+import better_parser.PrologParser
+
+class SourceFileReader {
+    private val parser = PrologParser()
+
+    fun readFile(filePath: String) {
+        return try {
+            val file = java.io.File(filePath)
+            if (!file.exists()) {
+                throw IllegalArgumentException("File not found: $filePath")
+            }
+
+            val content = file.readText()
+
+            // Parse the content using SimpleSourceParser
+            parser.parse(content)
+        } catch (e: Exception) {
+            throw RuntimeException("Error reading file: $filePath", e)
+        }
+    }
+}

src/prolog/Program.kt

@@ -1,5 +1,6 @@
 package prolog
 
+import Debug
 import prolog.ast.logic.Clause
 import prolog.ast.logic.Predicate
 import prolog.ast.logic.Resolvent
@@ -12,13 +13,16 @@ typealias Database = Program
  * Prolog Program or database.
  */
 object Program: Resolvent {
-    private var predicates: Map<Functor, Predicate> = emptyMap()
+    var predicates: Map<Functor, Predicate> = emptyMap()
 
     init {
         setup()
     }
 
     private fun setup() {
+        if (Debug.on) {
+            println("Setting up Prolog program...")
+        }
         // Initialize the program with built-in predicates
         load(listOf(
         ))

src/prolog/ast/logic/Clause.kt

@@ -18,7 +18,7 @@ import prolog.logic.unifyLazy
  * @see [prolog.ast.terms.Variable]
  * @see [Predicate]
  */
-abstract class Clause(private val head: Head, private val body: Body) : Resolvent {
+abstract class Clause(val head: Head, val body: Body) : Resolvent {
     val functor: Functor = head.functor
 
     override fun solve (goal: Goal, subs: Substitutions): Answers = sequence {

src/prolog/ast/logic/Predicate.kt

@@ -39,6 +39,11 @@ class Predicate : Resolvent {
      */
     fun add(clause: Clause) {
         require(clause.functor == functor) { "Clause functor does not match predicate functor" }
+
+        if (Debug.on) {
+            println("Adding clause $clause to predicate $functor")
+        }
+
         clauses.add(clause)
     }
 

src/prolog/ast/terms/Operator.kt

@@ -1,7 +1,5 @@
 package prolog.ast.terms
 
-import prolog.ast.arithmetic.Expression
-
 typealias Operand = Term
 
 abstract class Operator(

src/prolog/builtins/controlOperators.kt

@@ -39,7 +39,7 @@ class Cut() : Atom("!") {
 /**
  * Conjunction (and). True if both Goal1 and Goal2 are true.
  */
-class Conjunction(private val left: LogicOperand, private val right: LogicOperand) :
+class Conjunction(val left: LogicOperand, private val right: LogicOperand) :
     LogicOperator(Atom(","), left, right) {
     override fun satisfy(subs: Substitutions): Answers = sequence {
         // Satisfy the left part first, which either succeeds or fails

src/repl/Repl.kt

@@ -0,0 +1,4 @@
+package repl
+
+class Repl {
+}