feat: allow reset all global variable

Author: bdeneux

engine/vm.go

@@ -6,7 +6,6 @@ import (
 	"io"
 	"io/fs"
 	"strings"
-	"sync/atomic"
 )
 
 type bytecode []instruction
@@ -303,8 +302,17 @@ func (vm *VM) SetUserOutput(s *Stream) {
 	vm.output = s
 }
 
-func (vm *VM) ResetVariableCounter() {
-	atomic.StoreInt64(&varCounter, 1) // Set the varCounter to 1 instead of 0 because NewVariable() will first increment this counter and a global root variable has already been set to 1. (See engine/env.go L3)
+// ResetEnv is used to reset all global variable
+func (vm *VM) ResetEnv() {
+	varCounter = 0
+	varContext = NewVariable()
+	rootContext = NewAtom("root")
+	rootEnv = &Env{
+		binding: binding{
+			key:   newEnvKey(varContext),
+			value: rootContext,
+		},
+	}
 }
 
 // Predicate0 is a predicate of arity 0.

interpreter.go

@@ -23,14 +23,14 @@ type Interpreter struct {
 // NewEmpty creates a new Prolog interpreter without any predicates/operators defined.
 func NewEmpty() *Interpreter {
 	var i Interpreter
-	i.ResetVariableCounter()
+	i.ResetEnv()
 	return &i
 }
 
 // New creates a new Prolog interpreter with predefined predicates/operators.
 func New(in io.Reader, out io.Writer) *Interpreter {
 	var i Interpreter
-	i.ResetVariableCounter()
+	i.ResetEnv()
 	i.FS = defaultFS{}
 	i.SetUserInput(engine.NewInputTextStream(in))
 	i.SetUserOutput(engine.NewOutputTextStream(out))