init commit

Author: arjunsk

README.md

@@ -6,4 +6,50 @@ and [Arrow DataFusion](https://github.com/apache/arrow-datafusion).
 ### Why Dataframe
 
 Dataframe removes the complexity of handling `SQL parsing`, `SQL rewriting`, `Binding`, `SQL Query Planner` etc. Once
-the dataframe is mature, we can easily integrate it with an SQL engine.
+the dataframe is mature, we can easily integrate it with an SQL engine.
+
+
+### Example
+
+```go
+package main
+
+import (
+	"fmt"
+	"tiny_dataframe/pkg/a_engine"
+	logicalplan "tiny_dataframe/pkg/c_logical_plan"
+)
+
+func main() {
+	ctx := engine.NewContext()
+	df, _ := ctx.Parquet("../../test/data/c1_c2_int64.parquet", nil)
+	
+	df = df.
+		Project(
+			logicalplan.Column{Name: "c1"},
+			logicalplan.Column{Name: "c2"},
+		).
+		Filter(logicalplan.Eq(
+			logicalplan.Column{Name: "c1"},
+			logicalplan.LiteralInt64{Val: 100},
+		))
+
+	logicalPlan, _ := df.LogicalPlan()
+	fmt.Println(logicalplan.PrettyPrint(logicalPlan, 0))
+	/*
+	Filter: #c1 = 100
+		Projection: #c1, #c2
+			Input: ../../test/data/c1_c2_int64.parquet; projExpr=None
+	*/
+
+	_ = df.Show()
+	/*
+	+-----+-----+
+	| C1  | C2  |
+	+-----+-----+
+	| 100 | 101 |
+	+-----+-----+
+	*/
+}
+
+```

pkg/a_engine/engine_test.go cmd/simple/engine_test.gopkg/a_engine/engine_test.go renamed to cmd/simple/engine_test.go

@@ -1,13 +1,14 @@
-package engine
+package simple
 
 import (
 	"fmt"
 	"testing"
+	"tiny_dataframe/pkg/a_engine"
 	logicalplan "tiny_dataframe/pkg/c_logical_plan"
 )
 
 func TestParquetFile(t *testing.T) {
-	ctx := NewContext()
+	ctx := engine.NewContext()
 	df, err := ctx.Parquet("../../test/data/c1_c2_int64.parquet", nil)
 	if err != nil {
 		t.Error(err)