Cleanup 3

src/prolog/builtins/arithmeticOperators.kt

@@ -122,6 +122,11 @@ open class Add(private val expr1: Expression, private val expr2: Expression) :
     )
 }
 
+class Plus(private val expr1: Expression, private val expr2: Expression, private val expr3: Expression) :
+    CompoundTerm("plus", expr1, expr2, expr3) {
+    override fun satisfy(subs: Substitutions): Answers = plus(expr1, expr2, expr3, subs)
+}
+
 /**
  * Result = Expr1 - Expr2
  */

src/prolog/builtins/delimitedContinuationsOperators.kt

@@ -3,7 +3,6 @@ package prolog.builtins
 import prolog.Answers
 import prolog.Substitutions
 import prolog.ast.arithmetic.Integer
-import prolog.ast.terms.Atom
 import prolog.ast.terms.Goal
 import prolog.ast.terms.Structure
 import prolog.ast.terms.Term

src/prolog/builtins/loadingSourceOperators.kt

@@ -0,0 +1,39 @@
+package prolog.builtins
+
+import interpreter.FileLoader
+import prolog.Answers
+import prolog.Substitutions
+import prolog.ast.logic.LogicOperand
+import prolog.ast.logic.LogicOperator
+import prolog.ast.terms.Atom
+import prolog.ast.terms.Operator
+import prolog.ast.terms.Term
+import prolog.logic.applySubstitution
+
+class Consult(val file: Term) : Operator("consult", rightOperand = file) {
+    private val fileLoader = FileLoader()
+
+    override fun satisfy(subs: Substitutions): Answers {
+        val fileAtom = applySubstitution(file, subs)
+        require(fileAtom is Atom) { "File name must be an atom" }
+
+        var filePath = fileAtom.name
+        if (!filePath.endsWith(".pl")) {
+            filePath += ".pl"
+        }
+
+        try {
+            fileLoader.load(filePath)
+            return sequenceOf(Result.success(emptyMap()))
+        } catch (e: Exception) {
+            return sequenceOf(Result.failure(e))
+        }
+    }
+
+    override fun toString(): String = "consult($file)"
+}
+
+class Initialization(val goal: LogicOperand) : LogicOperator(":-", rightOperand = goal) {
+    override fun satisfy(subs: Substitutions): Answers = goal.satisfy(subs).take(1)
+    override fun toString(): String = goal.toString()
+}

src/prolog/builtins/metaOperators.kt

@@ -2,7 +2,6 @@ package prolog.builtins
 
 import prolog.Answers
 import prolog.Substitutions
-import prolog.ast.terms.Atom
 import prolog.ast.terms.Goal
 import prolog.ast.terms.Operator
 import prolog.ast.terms.Term
@@ -16,10 +15,18 @@ class Call(private val goal: Term) : Operator("call", rightOperand = goal) {
     }
 }
 
+/**
+ * Make a possibly nondeterministic [Goal] semideterministic, i.e. succeed at most once.
+ */
+class Once(private val goal: Term) : Operator("once", rightOperand = goal) {
+    private val conjunction = Conjunction(Call(goal), Cut())
+    override fun satisfy(subs: Substitutions): Answers = conjunction.satisfy(subs).take(1)
+}
+
 /**
  * Calls [Goal] once, but succeeds, regardless of whether Goal succeeded or not.
  */
-class Ignore(goal: Goal) : Operator("ignore", rightOperand = goal) {
+class Ignore(goal: Term) : Operator("ignore", rightOperand = goal) {
     private val disjunction = Disjunction(
         Conjunction(Call(goal), Cut()),
         True

src/prolog/builtins/other.kt

@@ -6,11 +6,6 @@ import prolog.ast.logic.LogicOperand
 import prolog.ast.logic.LogicOperator
 import prolog.ast.terms.Goal
 
-class Initialization(val goal: LogicOperand) : LogicOperator(":-", rightOperand = goal) {
-    override fun satisfy(subs: Substitutions): Answers = goal.satisfy(subs).take(1)
-    override fun toString(): String = goal.toString()
-}
-
 class Query(val query: LogicOperand) : LogicOperator("?-", rightOperand = query) {
     override fun satisfy(subs: Substitutions): Answers = query.satisfy(subs)
 }