Checkpoint

src/prolog/builtins/arithmeticOperators.kt

@@ -0,0 +1,152 @@
+package prolog.builtins
+
+import prolog.ast.arithmetic.ArithmeticOperator
+import prolog.ast.arithmetic.Expression
+import prolog.ast.logic.LogicOperand
+import prolog.ast.logic.LogicOperator
+import prolog.ast.logic.Provable
+import prolog.ast.terms.*
+import prolog.logic.*
+
+// TODO >
+
+// TODO <
+
+// TODO =<
+
+// TODO >=
+
+/**
+ * True if expression Expr1 evaluates to a number non-equal to Expr2.
+ */
+class EvaluatesToDifferent(private val left: Expression, private val right: Expression) :
+    ArithmeticOperator(Atom("=\\="), left, right) {
+    override fun evaluate(subs: Substituted): Pair<Term, Substituted> {
+        val t1 = left.evaluate(subs)
+        val t2 = right.evaluate(subs)
+
+        // Should both be instantiated
+        if (!atomic(t1.first) || !atomic(t2.first)) {
+            throw IllegalArgumentException("Both operands must be instantiated")
+        }
+
+        return if (equivalent(t1.first, t2.first)) {
+            Pair(False, emptyMap())
+        } else {
+            Pair(True, t1.second + t2.second)
+        }
+    }
+
+}
+
+/**
+ * True if Expr1 evaluates to a number equal to Expr2.
+ */
+class EvaluatesTo(private val left: Expression, private val right: Expression) :
+    ArithmeticOperator(Atom("=:="), left, right) {
+    override fun evaluate(subs: Substituted): Pair<Term, Substituted> {
+        val t1 = left.evaluate(subs)
+        val t2 = right.evaluate(subs)
+
+        // Should both be instantiated
+        if (!atomic(t1.first) || !atomic(t2.first)) {
+            throw IllegalArgumentException("Both operands must be instantiated")
+        }
+
+        return if (equivalent(t1.first, t2.first)) {
+            Pair(True, t1.second + t2.second)
+        } else {
+            Pair(False, emptyMap())
+        }
+    }
+}
+
+/**
+ * True when Number is the value to which Expr evaluates.
+ */
+class Is(private val left: Expression, private val right: Expression) :
+    Operator(Atom("is"), left, right), Provable {
+    override fun prove(subs: Substituted): Sequence<Substituted> {
+        val t1 = left.evaluate(subs)
+        val t2 = right.evaluate(subs)
+
+        if (!atomic(t2.first)) {
+            throw IllegalArgumentException("Arguments are not sufficiently instantiated")
+        }
+
+        return unifyLazy(t1.first, t2.first, subs).map{ it + t1.second + t2.second }
+    }
+}
+
+/**
+ * Result = -Expr
+ */
+class Negate(operand: Expression) : Subtract(Integer(0), operand)
+
+/**
+ * Result = Expr
+ */
+class Positive(operand: Expression) : Add(Integer(0), operand)
+
+/**
+ * Result = Expr1 + Expr2
+ */
+open class Add(private val expr1: Expression, private val expr2: Expression) :
+    ArithmeticOperator(Atom("+"), expr1, expr2) {
+    override fun evaluate(subs: Substituted): Pair<Term, Substituted> {
+        val result = Variable("Result")
+        val map = plus(expr1, expr2, result, subs)
+        return result.evaluate(map.first())
+    }
+}
+
+/**
+ * Result = Expr1 - Expr2
+ */
+open class Subtract(private val expr1: Expression, private val expr2: Expression) :
+    ArithmeticOperator(Atom("-"), expr1, expr2) {
+    override fun evaluate(subs: Substituted): Pair<Term, Substituted> {
+        val result = Variable("Result")
+        val map = plus(expr2, result, expr1, subs)
+        return result.evaluate(map.first())
+    }
+}
+
+// TODO Expr * Expr
+/**
+ * Result = Expr1 * Expr2
+ */
+class Multiply(private val expr1: Expression, private val expr2: Expression) :
+    ArithmeticOperator(Atom("*"), expr1, expr2) {
+    override fun evaluate(subs: Substituted): Pair<Term, Substituted> {
+        val result = Variable("Result")
+        val map = mul(expr1, expr2, result, subs)
+        return result.evaluate(map.first())
+    }
+}
+
+// TODO Expr / Expr
+
+// TODO Expr mod Expr
+
+// TODO Expr rem Expr
+
+class Between(private val expr1: Expression, private val expr2: Expression, private val expr3: Expression) :
+    Operator(Atom("between"), expr1, expr2) {
+    override fun prove(subs: Substituted): Sequence<Substituted> {
+        val e1 = expr1.evaluate(subs)
+        val e2 = expr2.evaluate(subs)
+        val e3 = expr3.evaluate(subs)
+
+        require(e1.first is Integer && e2.first is Integer) { "Arguments must be integers" }
+
+        val v1 = e1.first as Integer
+        val v2 = e2.first as Integer
+
+        return if (variable(e3.first)) {
+            between(v1, v2, e3.first as Variable).map { it + e1.second + e2.second }
+        } else {
+            between(v1, v2, e3.first as Integer).map { it + e1.second + e2.second }
+        }
+    }
+}