Moving main to its own package (#11)

README.md

@@ -54,5 +54,11 @@ pr: present
 not: not of a logical expression
 ```
 
+## How to use it 
+Use your dependency manager to import `github.com/nikunjy/rules/parser`. This will let you parse a rule and keep the parsed representation around. 
+Alternatively, you can also use `github.com/nikunjy/rules` directly to call the root `Evaluate(string, map[string]interface{})` method. 
+
+I would recommend importing `github.com/nikunjy/rules/parser` 
+
 [ci-img]: https://api.travis-ci.org/nikunjy/rules.svg?branch=master
 [ci]: https://travis-ci.org/nikunjy/rules

evaluate.go

@@ -0,0 +1,11 @@
+package rules
+
+import "github.com/nikunjy/rules/parser"
+
+func Evaluate(rule string, items map[string]interface{}) (bool, error) {
+	ev, err := parser.NewEvaluator(rule)
+	if err != nil {
+		return false, err
+	}
+	return ev.Process(items)
+}

evaluate_test.go

@@ -0,0 +1,21 @@
+package rules
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/require"
+)
+
+func TestEvaluateBasic(t *testing.T) {
+	res, err := Evaluate(`x eq "abc"`, map[string]interface{}{
+		"x": "abc",
+	})
+	require.NoError(t, err)
+	require.True(t, res)
+
+	res, err = Evaluate(`x eq abc`, map[string]interface{}{
+		"x": "abc",
+	})
+	require.Error(t, err)
+	require.False(t, res)
+}