Fix/306and307 Will fix #306 and #307 (#306)

* Better make file

* Added samples

* Taking the oportunity in this branch to fix some documentation issue

* Fixed issue 306 and 307, due to wrong logic when adding ArrayMapSelector ast into ExpressionAtom

* Removed unnecessary dummy file

ast/ExpressionAtom.go

@@ -234,7 +234,8 @@ func (e *ExpressionAtom) GetSnapshot() string {
 		buff.WriteString(e.ExpressionAtom.GetSnapshot())
 		buff.WriteString("->MV:")
 		buff.WriteString(e.VariableName)
-	} else if e.ArrayMapSelector != nil && e.ExpressionAtom != nil {
+	}
+	if e.ArrayMapSelector != nil && e.ExpressionAtom != nil {
 		buff.WriteString(e.ExpressionAtom.GetSnapshot())
 		buff.WriteString("-[]>")
 		buff.WriteString(e.ArrayMapSelector.GetSnapshot())

ast/WorkingMemory.go

@@ -144,7 +144,7 @@ func (e *WorkingMemory) Clone(cloneTable *pkg.CloneTable) *WorkingMemory {
 			if cloneTable.IsCloned(expr.AstID) {
 				clone.expressionSnapshotMap[k] = cloneTable.Records[expr.AstID].CloneInstance.(*Expression)
 			} else {
-				panic(fmt.Sprintf("expression  %s is not on the clone table", expr.GrlText))
+				panic(fmt.Sprintf("expression  %s is not on the clone table - %s", expr.GrlText, expr.GetSnapshot()))
 			}
 		}
 	}

examples/CloneTableIssue_test.go

@@ -0,0 +1,44 @@
+package examples
+
+import (
+	"github.com/hyperjumptech/grule-rule-engine/ast"
+	"github.com/hyperjumptech/grule-rule-engine/builder"
+	"github.com/hyperjumptech/grule-rule-engine/engine"
+	"github.com/hyperjumptech/grule-rule-engine/pkg"
+	"github.com/stretchr/testify/assert"
+	"testing"
+)
+
+type StructStringsData struct {
+	Strings []string
+}
+
+func (f *StructStringsData) GetStrings() []string {
+	return f.Strings
+}
+
+const panickingRule = ` rule test {
+when 
+	Fact.GetStrings()[0] == Fact.GetStrings()[1]
+then
+	Complete();
+}`
+
+func TestSliceFunctionPanicTest(t *testing.T) {
+	fact := &StructStringsData{
+		Strings: []string{"0", "0"},
+	}
+
+	dataContext := ast.NewDataContext()
+	err := dataContext.Add("Fact", fact)
+	assert.NoError(t, err)
+	knowledgeLibrary := ast.NewKnowledgeLibrary()
+	ruleBuilder := builder.NewRuleBuilder(knowledgeLibrary)
+	err = ruleBuilder.BuildRuleFromResource("test", "0.0.1", pkg.NewBytesResource([]byte(panickingRule)))
+	assert.NoError(t, err)
+	knowledgeBase := knowledgeLibrary.NewKnowledgeBaseInstance("test", "0.0.1")
+	engine := engine.NewGruleEngine()
+
+	err = engine.Execute(dataContext, knowledgeBase)
+	assert.NoError(t, err)
+}

examples/MemoizeSliceFunction_test.go

@@ -0,0 +1,49 @@
+package examples
+
+import (
+	"github.com/hyperjumptech/grule-rule-engine/ast"
+	"github.com/hyperjumptech/grule-rule-engine/builder"
+	"github.com/hyperjumptech/grule-rule-engine/engine"
+	"github.com/hyperjumptech/grule-rule-engine/pkg"
+	"github.com/stretchr/testify/assert"
+	"testing"
+)
+
+type TestData struct {
+	Index         int
+	Strings       []string
+	Concatenation string
+}
+
+func (f *TestData) GetStrings() []string {
+	return f.Strings
+}
+
+const rule = ` rule test {
+when 
+	Fact.Index < Fact.Strings.Len()
+then
+	Fact.Concatenation = Fact.Concatenation + Fact.GetStrings()[Fact.Index];
+	Fact.Index = Fact.Index + 1;
+}`
+
+func TestSliceFunctionTest(t *testing.T) {
+	fact := &TestData{
+		Index:   0,
+		Strings: []string{"1", "2", "3"},
+	}
+
+	dataContext := ast.NewDataContext()
+	err := dataContext.Add("Fact", fact)
+	assert.NoError(t, err)
+	knowledgeLibrary := ast.NewKnowledgeLibrary()
+	ruleBuilder := builder.NewRuleBuilder(knowledgeLibrary)
+	err = ruleBuilder.BuildRuleFromResource("test", "0.0.1", pkg.NewBytesResource([]byte(rule)))
+	assert.NoError(t, err)
+	knowledgeBase := knowledgeLibrary.NewKnowledgeBaseInstance("test", "0.0.1")
+	engine := engine.NewGruleEngine()
+
+	err = engine.Execute(dataContext, knowledgeBase)
+	assert.NoError(t, err)
+	assert.Equal(t, "123", fact.Concatenation)
+}