Arithmetic preprocessing

src/interpreter/Preprocessor.kt

@@ -1,24 +1,13 @@
 package interpreter
 
 import io.Logger
+import prolog.ast.arithmetic.Expression
 import prolog.ast.logic.Clause
 import prolog.ast.logic.Fact
 import prolog.ast.logic.LogicOperand
 import prolog.ast.logic.Rule
-import prolog.ast.terms.Atom
+import prolog.ast.terms.*
-import prolog.ast.terms.Body
+import prolog.builtins.*
-import prolog.ast.terms.Goal
-import prolog.ast.terms.Head
-import prolog.ast.terms.Structure
-import prolog.ast.terms.Term
-import prolog.builtins.Conjunction
-import prolog.builtins.Cut
-import prolog.builtins.Disjunction
-import prolog.builtins.Fail
-import prolog.builtins.False
-import prolog.builtins.Not
-import prolog.builtins.Query
-import prolog.builtins.True
 
 /**
  * Preprocessor for Prolog
@@ -45,12 +34,14 @@ open class Preprocessor {
             is Fact -> {
                 Fact(preprocess(clause.head) as Head)
             }
+
             is Rule -> {
                 Rule(
                     preprocess(clause.head) as Head,
                     preprocess(clause.body as Term) as Body
                 )
             }
+
             else -> clause
         }
     }
@@ -65,23 +56,70 @@ open class Preprocessor {
             Structure(Atom("fail"), emptyList()) -> Fail
             Atom("!") -> Cut()
             Structure(Atom("!"), emptyList()) -> Cut()
-            else -> {
+            is Structure -> {
-                when {
+                // Preprocess the arguments first to recognize builtins
-                    term is Structure && term.functor == ",/2" -> {
                 val args = term.arguments.map { preprocess(it) }
+
+                when {
+                    // TODO Remove hardcoding by storing the functors as constants in operators?
+                    // Logic
+                    term.functor == ",/2" -> {
                         Conjunction(args[0] as LogicOperand, args[1] as LogicOperand)
                     }
-                    term is Structure && term.functor == ";/2" -> {
+
-                        val args = term.arguments.map { preprocess(it) }
+                    term.functor == ";/2" -> {
                         Disjunction(args[0] as LogicOperand, args[1] as LogicOperand)
                     }
-                    term is Structure && term.functor == "\\+/1" -> {
+
-                        val args = term.arguments.map { preprocess(it) }
+                    term.functor == "\\+/1" -> {
                         Not(args[0] as Goal)
                     }
+                    // Arithmetic
+                    term.functor == "=\\=/2" && args.all { it is Expression } -> {
+                        EvaluatesToDifferent(args[0] as Expression, args[1] as Expression)
+                    }
+
+                    term.functor == "=:=/2" && args.all { it is Expression } -> {
+                        EvaluatesTo(args[0] as Expression, args[1] as Expression)
+                    }
+
+                    term.functor == "is/2" && args.all { it is Expression } -> {
+                        Is(args[0] as Expression, args[1] as Expression)
+                    }
+
+                    term.functor == "-/1" && args.all { it is Expression } -> {
+                        Negate(args[0] as Expression)
+                    }
+
+                    term.functor == "-/2" && args.all { it is Expression } -> {
+                        Subtract(args[0] as Expression, args[1] as Expression)
+                    }
+
+                    term.functor == "+/1" && args.all { it is Expression } -> {
+                        Positive(args[0] as Expression)
+                    }
+
+                    term.functor == "+/2" && args.all { it is Expression } -> {
+                        Add(args[0] as Expression, args[1] as Expression)
+                    }
+
+                    term.functor == "*/2" && args.all { it is Expression } -> {
+                        Multiply(args[0] as Expression, args[1] as Expression)
+                    }
+
+                    term.functor == "//2" && args.all { it is Expression } -> {
+                        Divide(args[0] as Expression, args[1] as Expression)
+                    }
+
+                    term.functor == "between/3" && args.all { it is Expression } -> {
+                        Between(args[0] as Expression, args[1] as Expression, args[2] as Expression)
+                    }
+
                     else -> term
                 }
             }
+
+            else -> term
         }
 
         if (prepped != term || prepped::class != term::class) {

src/prolog/builtins/arithmeticOperators.kt

@@ -62,11 +62,11 @@ class EvaluatesTo(private val left: Expression, private val right: Expression) :
 /**
  * True when Number is the value to which Expr evaluates.
  */
-class Is(private val left: Expression, private val right: Expression) :
+class Is(val number: Expression, val expr: Expression) :
-    Operator(Atom("is"), left, right), Satisfiable {
+    Operator(Atom("is"), number, expr), Satisfiable {
     override fun satisfy(subs: Substitutions): Answers {
-        val t1 = left.simplify(subs)
+        val t1 = number.simplify(subs)
-        val t2 = right.simplify(subs)
+        val t2 = expr.simplify(subs)
 
         if (!atomic(t2.to, subs)) {
             return sequenceOf(Result.failure(IllegalArgumentException("Right operand must be instantiated")))
@@ -119,7 +119,7 @@ open class Subtract(private val expr1: Expression, private val expr2: Expression
 /**
  * Result = Expr1 * Expr2
  */
-class Multiply(private val expr1: Expression, private val expr2: Expression) :
+class Multiply(val expr1: Expression, val expr2: Expression) :
     ArithmeticOperator(Atom("*"), expr1, expr2) {
     override fun simplify(subs: Substitutions): Simplification {
         val result = Variable("Result")

tests/interpreter/PreprocessorTests.kt

@@ -3,15 +3,12 @@ package interpreter
 import org.junit.jupiter.api.Assertions.assertEquals
 import org.junit.jupiter.api.Nested
 import org.junit.jupiter.api.Test
+import prolog.ast.arithmetic.Integer
 import prolog.ast.terms.Atom
 import prolog.ast.terms.CompoundTerm
 import prolog.ast.terms.Term
-import prolog.builtins.Conjunction
+import prolog.ast.terms.Variable
-import prolog.builtins.Disjunction
+import prolog.builtins.*
-import prolog.builtins.Cut
-import prolog.builtins.Fail
-import prolog.builtins.True
-import prolog.builtins.Not
 
 class PreprocessorTests {
     class OpenPreprocessor : Preprocessor() {
@@ -20,11 +17,318 @@ class PreprocessorTests {
         }
     }
 
+    companion object {
+        fun test(tests: Map<Term, Term>) {
+            for ((input, expected) in tests) {
+                val result = OpenPreprocessor().preprocess(input)
+                assertEquals(expected, result, "Expected preprocessed")
+                assertEquals(expected::class, result::class, "Expected same class")
+            }
+        }
+    }
+
     @Nested
     class `Arithmetic operators` {
         @Test
         fun `evaluates to different`() {
-            assertEquals(1, 2)
+            test(
+                mapOf(
+                    Atom("=\\=") to Atom("=\\="),
+                    CompoundTerm(Atom("=\\="), emptyList()) to CompoundTerm(Atom("=\\="), emptyList()),
+                    Atom("EvaluatesToDifferent") to Atom("EvaluatesToDifferent"),
+                    CompoundTerm(Atom("EvaluatesToDifferent"), emptyList()) to CompoundTerm(
+                        Atom("EvaluatesToDifferent"),
+                        emptyList()
+                    ),
+                    CompoundTerm(Atom("=\\="), listOf(Atom("a"))) to CompoundTerm(
+                        Atom("=\\="),
+                        listOf(Atom("a"))
+                    ),
+                    CompoundTerm(Atom("=\\="), listOf(Integer(1))) to CompoundTerm(
+                        Atom("=\\="),
+                        listOf(Integer(1))
+                    ),
+                    CompoundTerm(Atom("=\\="), listOf(Atom("=\\="))) to CompoundTerm(
+                        Atom("=\\="),
+                        listOf(Atom("=\\="))
+                    ),
+                    CompoundTerm(Atom("=\\="), listOf(Integer(1), Integer(2))) to EvaluatesToDifferent(
+                        Integer(1), Integer(2)
+                    )
+                )
+            )
+        }
+
+        @Test
+        fun `evaluates to`() {
+            test(
+                mapOf(
+                    Atom("=:=") to Atom("=:="),
+                    CompoundTerm(Atom("=:="), emptyList()) to CompoundTerm(Atom("=:="), emptyList()),
+                    Atom("EvaluatesTo") to Atom("EvaluatesTo"),
+                    CompoundTerm(Atom("EvaluatesTo"), emptyList()) to CompoundTerm(
+                        Atom("EvaluatesTo"),
+                        emptyList()
+                    ),
+                    CompoundTerm(Atom("=:="), listOf(Atom("a"))) to CompoundTerm(
+                        Atom("=:="),
+                        listOf(Atom("a"))
+                    ),
+                    CompoundTerm(Atom("=:="), listOf(Atom("=:="))) to CompoundTerm(
+                        Atom("=:="),
+                        listOf(Atom("=:="))
+                    ),
+                    CompoundTerm(Atom("=:="), listOf(Integer(1), Integer(2))) to EvaluatesTo(
+                        Integer(1), Integer(2)
+                    )
+                )
+            )
+        }
+
+        @Test
+        fun `is`() {
+            test(
+                mapOf(
+                    Atom("is") to Atom("is"),
+                    CompoundTerm(Atom("is"), emptyList()) to CompoundTerm(Atom("is"), emptyList()),
+                    Atom("Is") to Atom("Is"),
+                    CompoundTerm(Atom("Is"), emptyList()) to CompoundTerm(Atom("Is"), emptyList()),
+                    CompoundTerm(Atom("is"), listOf(Atom("a"))) to CompoundTerm(
+                        Atom("is"),
+                        listOf(Atom("a"))
+                    ),
+                    CompoundTerm(Atom("is"), listOf(Integer(1))) to CompoundTerm(
+                        Atom("is"),
+                        listOf(Integer(1))
+                    ),
+                    CompoundTerm(Atom("is"), listOf(Atom("is"))) to CompoundTerm(
+                        Atom("is"),
+                        listOf(Atom("is"))
+                    ),
+                    CompoundTerm(Atom("is"), listOf(Integer(1), Integer(2))) to Is(
+                        Integer(1), Integer(2)
+                    )
+                )
+            )
+        }
+
+        @Test
+        fun `negate and subtract`() {
+            test(
+                mapOf(
+                    Atom("-") to Atom("-"),
+                    CompoundTerm(Atom("-"), emptyList()) to CompoundTerm(Atom("-"), emptyList()),
+                    Atom("Negate") to Atom("Negate"),
+                    CompoundTerm(Atom("Negate"), emptyList()) to CompoundTerm(
+                        Atom("Negate"),
+                        emptyList()
+                    ),
+                    CompoundTerm(Atom("-"), listOf(Atom("a"))) to CompoundTerm(
+                        Atom("-"),
+                        listOf(Atom("a"))
+                    ),
+                    CompoundTerm(Atom("-"), listOf(Integer(1))) to Negate(Integer(1)),
+                    CompoundTerm(Atom("-"), listOf(Atom("-"))) to CompoundTerm(
+                        Atom("-"),
+                        listOf(Atom("-"))
+                    ),
+                    CompoundTerm(Atom("-"), listOf(Integer(1), Integer(2))) to Subtract(
+                        Integer(1), Integer(2)
+                    ),
+                    CompoundTerm(Atom("-"), listOf(Atom("1"), Atom("2"))) to CompoundTerm(
+                        Atom("-"),
+                        listOf(Atom("1"), Atom("2"))
+                    ),
+                    CompoundTerm(Atom("-"), listOf(Integer(1), Integer(2), Integer(3))) to CompoundTerm(
+                        Atom("-"),
+                        listOf(Integer(1), Integer(2), Integer(3))
+                    )
+                )
+            )
+        }
+
+        @Test
+        fun `positive and add`() {
+            test(
+                mapOf(
+                    Atom("+") to Atom("+"),
+                    CompoundTerm(Atom("+"), emptyList()) to CompoundTerm(Atom("+"), emptyList()),
+                    Atom("Positive") to Atom("Positive"),
+                    CompoundTerm(Atom("Positive"), emptyList()) to CompoundTerm(
+                        Atom("Positive"),
+                        emptyList()
+                    ),
+                    CompoundTerm(Atom("+"), listOf(Atom("a"))) to CompoundTerm(
+                        Atom("+"),
+                        listOf(Atom("a"))
+                    ),
+                    CompoundTerm(Atom("+"), listOf(Integer(1))) to Positive(Integer(1)),
+                    CompoundTerm(Atom("+"), listOf(Atom("+"))) to CompoundTerm(
+                        Atom("+"),
+                        listOf(Atom("+"))
+                    ),
+                    CompoundTerm(Atom("+"), listOf(Integer(1), Integer(2))) to Add(
+                        Integer(1), Integer(2)
+                    ),
+                    CompoundTerm(Atom("+"), listOf(Atom("1"), Atom("2"))) to CompoundTerm(
+                        Atom("+"),
+                        listOf(Atom("1"), Atom("2"))
+                    ),
+                    CompoundTerm(Atom("+"), listOf(Integer(1), Integer(2), Integer(3))) to CompoundTerm(
+                        Atom("+"),
+                        listOf(Integer(1), Integer(2), Integer(3))
+                    )
+                )
+            )
+        }
+
+        @Test
+        fun multiply() {
+            test(
+                mapOf(
+                    Atom("*") to Atom("*"),
+                    CompoundTerm(Atom("*"), emptyList()) to CompoundTerm(Atom("*"), emptyList()),
+                    Atom("Multiply") to Atom("Multiply"),
+                    CompoundTerm(Atom("Multiply"), emptyList()) to CompoundTerm(
+                        Atom("Multiply"),
+                        emptyList()
+                    ),
+                    CompoundTerm(Atom("*"), listOf(Atom("a"))) to CompoundTerm(
+                        Atom("*"),
+                        listOf(Atom("a"))
+                    ),
+                    CompoundTerm(Atom("*"), listOf(Integer(1))) to CompoundTerm(Atom("*"), listOf(Integer(1))),
+                    CompoundTerm(Atom("*"), listOf(Atom("*"))) to CompoundTerm(
+                        Atom("*"),
+                        listOf(Atom("*"))
+                    ),
+                    CompoundTerm(Atom("*"), listOf(Integer(1), Integer(2))) to Multiply(
+                        Integer(1), Integer(2)
+                    ),
+                    CompoundTerm(Atom("*"), listOf(Atom("1"), Atom("2"))) to CompoundTerm(
+                        Atom("*"),
+                        listOf(Atom("1"), Atom("2"))
+                    ),
+                    CompoundTerm(Atom("*"), listOf(Integer(1), Integer(2), Integer(3))) to CompoundTerm(
+                        Atom("*"),
+                        listOf(Integer(1), Integer(2), Integer(3))
+                    )
+                )
+            )
+        }
+
+        @Test
+        fun divide() {
+            test(
+                mapOf(
+                    Atom("/") to Atom("/"),
+                    CompoundTerm(Atom("/"), emptyList()) to CompoundTerm(Atom("/"), emptyList()),
+                    Atom("Divide") to Atom("Divide"),
+                    CompoundTerm(Atom("Divide"), emptyList()) to CompoundTerm(
+                        Atom("Divide"),
+                        emptyList()
+                    ),
+                    CompoundTerm(Atom("/"), listOf(Atom("a"))) to CompoundTerm(
+                        Atom("/"),
+                        listOf(Atom("a"))
+                    ),
+                    CompoundTerm(Atom("/"), listOf(Integer(1))) to CompoundTerm(Atom("/"), listOf(Integer(1))),
+                    CompoundTerm(Atom("/"), listOf(Atom("/"))) to CompoundTerm(
+                        Atom("/"),
+                        listOf(Atom("/"))
+                    ),
+                    CompoundTerm(Atom("/"), listOf(Integer(1), Integer(2))) to Divide(
+                        Integer(1), Integer(2)
+                    ),
+                    CompoundTerm(Atom("/"), listOf(Atom("1"), Atom("2"))) to CompoundTerm(
+                        Atom("/"),
+                        listOf(Atom("1"), Atom("2"))
+                    ),
+                    CompoundTerm(Atom("/"), listOf(Integer(1), Integer(2), Integer(3))) to CompoundTerm(
+                        Atom("/"),
+                        listOf(Integer(1), Integer(2), Integer(3))
+                    )
+                )
+            )
+        }
+
+        @Test
+        fun between() {
+            test(
+                mapOf(
+                    Atom("between") to Atom("between"),
+                    CompoundTerm(Atom("between"), emptyList()) to CompoundTerm(
+                        Atom("between"),
+                        emptyList()
+                    ),
+                    Atom("Between") to Atom("Between"),
+                    CompoundTerm(Atom("Between"), emptyList()) to CompoundTerm(
+                        Atom("Between"),
+                        emptyList()
+                    ),
+                    CompoundTerm(Atom("between"), listOf(Atom("a"))) to CompoundTerm(
+                        Atom("between"),
+                        listOf(Atom("a"))
+                    ),
+                    CompoundTerm(Atom("between"), listOf(Integer(1))) to CompoundTerm(
+                        Atom("between"),
+                        listOf(Integer(1))
+                    ),
+                    CompoundTerm(Atom("between"), listOf(Atom("between"))) to CompoundTerm(
+                        Atom("between"),
+                        listOf(Atom("between"))
+                    ),
+                    CompoundTerm(Atom("between"), listOf(Integer(1), Integer(2))) to CompoundTerm(
+                        Atom("between"),
+                        listOf(Integer(1), Integer(2))
+                    ),
+                    CompoundTerm(Atom("between"), listOf(Integer(1), Integer(2), Integer(3))) to Between(
+                        Integer(1), Integer(2), Integer(3)
+                    ),
+                )
+            )
+        }
+
+        @Test
+        fun `fun combinations`() {
+            /*
+             * [X - 1] is [(1 + 2) * ((12 / 3) - 0)]
+             * should return
+             * X = 13
+             */
+            val sum_ = CompoundTerm(Atom("+"), listOf(Integer(1), Integer(2)))
+            val sum = Add(Integer(1), Integer(2))
+
+            val div_ = CompoundTerm(Atom("/"), listOf(Integer(12), Integer(3)))
+            val div = Divide(Integer(12), Integer(3))
+
+            val sub_ = CompoundTerm(Atom("-"), listOf(div_, Integer(0)))
+            val sub = Subtract(div, Integer(0))
+
+            val right_ = CompoundTerm(Atom("*"), listOf(sum_, sub_))
+            val right = Multiply(sum, sub)
+
+            val left_ = CompoundTerm(Atom("-"), listOf(Variable("X"), Integer(1)))
+            val left = Subtract(Variable("X"), Integer(1))
+
+            val expr_ = CompoundTerm(Atom("is"), listOf(left_, right_))
+            val expr = Is(left, right)
+
+            val result = OpenPreprocessor().preprocess(expr_)
+
+            assertEquals(expr, result)
+            assertEquals(Is::class, result::class)
+            val `is` = result as Is
+
+            assertEquals(left, `is`.number)
+            assertEquals(Subtract::class, `is`.number::class)
+
+            assertEquals(right, `is`.expr)
+            assertEquals(Multiply::class, `is`.expr::class)
+            val multiply = `is`.expr as Multiply
+
+            assertEquals(sum, multiply.expr1)
+            assertEquals(Add::class, multiply.expr1::class)
         }
     }
 
@@ -34,7 +338,8 @@ class PreprocessorTests {
 
         @Test
         fun fail() {
-            val tests = mapOf(
+            test(
+                mapOf(
                     Atom("fail") to Fail,
                     CompoundTerm(Atom("fail"), emptyList()) to Fail,
                     Atom("Fail") to Atom("Fail"),
@@ -42,17 +347,13 @@ class PreprocessorTests {
                     CompoundTerm(Atom("fail"), listOf(Atom("a"))) to CompoundTerm(Atom("fail"), listOf(Atom("a"))),
                     CompoundTerm(Atom("fail"), listOf(Atom("fail"))) to CompoundTerm(Atom("fail"), listOf(Fail))
                 )
-
+            )
-            for ((input, expected) in tests) {
-                val result = preprocessor.preprocess(input)
-                assertEquals(expected, result, "Expected preprocessed")
-                assertEquals(expected::class, result::class, "Expected same class")
-            }
         }
 
         @Test
         fun `true`() {
-            val tests = mapOf(
+            test(
+                mapOf(
                     Atom("true") to True,
                     CompoundTerm(Atom("true"), emptyList()) to True,
                     Atom("True") to Atom("True"),
@@ -60,33 +361,25 @@ class PreprocessorTests {
                     CompoundTerm(Atom("true"), listOf(Atom("a"))) to CompoundTerm(Atom("true"), listOf(Atom("a"))),
                     CompoundTerm(Atom("true"), listOf(Atom("true"))) to CompoundTerm(Atom("true"), listOf(True))
                 )
-
+            )
-            for ((input, expected) in tests) {
-                val result = preprocessor.preprocess(input)
-                assertEquals(expected, result, "Expected preprocessed")
-                assertEquals(expected::class, result::class, "Expected same class")
-            }
         }
 
         @Test
         fun cut() {
-            val tests = mapOf(
+            test(
+                mapOf(
                     Atom("!") to Cut(),
                     CompoundTerm(Atom("!"), emptyList()) to Cut(),
                     CompoundTerm(Atom("!"), listOf(Atom("a"))) to CompoundTerm(Atom("!"), listOf(Atom("a"))),
                     CompoundTerm(Atom("!"), listOf(Atom("!"))) to CompoundTerm(Atom("!"), listOf(Cut()))
                 )
-
+            )
-            for ((input, expected) in tests) {
-                val result = preprocessor.preprocess(input)
-                assertEquals(expected, result, "Expected preprocessed")
-                assertEquals(expected::class, result::class, "Expected same class")
-            }
         }
 
         @Test
         fun conjunction() {
-            val tests = mapOf(
+            test(
+                mapOf(
                     CompoundTerm(Atom(","), listOf(Atom("a"), Atom("b"))) to Conjunction(Atom("a"), Atom("b")),
                     CompoundTerm(Atom(","), listOf(Atom("a"), Atom("b"), Atom("c"))) to CompoundTerm(
                         Atom(","),
@@ -98,17 +391,13 @@ class PreprocessorTests {
                         listOf(Atom("a"), CompoundTerm(Atom(","), listOf(Atom("b"), Atom("c"))))
                     ) to Conjunction(Atom("a"), Conjunction(Atom("b"), Atom("c"))),
                 )
-
+            )
-            for ((input, expected) in tests) {
-                val result = preprocessor.preprocess(input)
-                assertEquals(expected, result, "Expected preprocessed")
-                assertEquals(expected::class, result::class, "Expected same class")
-            }
         }
 
         @Test
         fun disjunction() {
-            val tests = mapOf(
+            test(
+                mapOf(
                     CompoundTerm(Atom(";"), listOf(Atom("a"), Atom("b"))) to Disjunction(Atom("a"), Atom("b")),
                     CompoundTerm(Atom(";"), listOf(Atom("a"), Atom("b"), Atom("c"))) to CompoundTerm(
                         Atom(";"),
@@ -120,17 +409,13 @@ class PreprocessorTests {
                         listOf(Atom("a"), CompoundTerm(Atom(";"), listOf(Atom("b"), Atom("c"))))
                     ) to Disjunction(Atom("a"), Disjunction(Atom("b"), Atom("c"))),
                 )
-
+            )
-            for ((input, expected) in tests) {
-                val result = preprocessor.preprocess(input)
-                assertEquals(expected, result, "Expected preprocessed")
-                assertEquals(expected::class, result::class, "Expected same class")
-            }
         }
 
         @Test
         fun not() {
-            val tests = mapOf(
+            test(
+                mapOf(
                     CompoundTerm(Atom("\\+"), listOf(Atom("a"))) to Not(Atom("a")),
                     CompoundTerm(Atom("\\+"), listOf(Atom("a"), Atom("b"))) to CompoundTerm(
                         Atom("\\+"),
@@ -145,12 +430,7 @@ class PreprocessorTests {
                         )
                     ) to CompoundTerm(Atom("foo"), listOf(Atom("bar"), Not(Not(Atom("baz"))))),
                 )
-
+            )
-            for ((input, expected) in tests) {
-                val result = preprocessor.preprocess(input)
-                assertEquals(expected, result, "Expected preprocessed")
-                assertEquals(expected::class, result::class, "Expected same class")
-            }
         }
     }
 }