增加 自定义函数注册

Author: dengsgo

engine/util_test.go

@@ -106,6 +106,16 @@ func TestParseAndExecTrigonometric(t *testing.T) {
 	}
 }
 
+func TestRegFunction(t *testing.T) {
+	RegFunction("double", 1, func(expr ...ExprAST) float64 {
+		return ExprASTResult(expr[0]) * 2
+	})
+	r, err := ParseAndExec("double(6)")
+	if r != 12 {
+		t.Error(err, "RegFunction errors when register new funtion")
+	}
+}
+
 func TestParseAndExecError(t *testing.T) {
 	exprs := []string{
 		"(",

main.go

@@ -3,10 +3,11 @@ package main
 import (
 	"bufio"
 	"fmt"
-	"github.com/dengsgo/math-engine/engine"
 	"os"
 	"strings"
 	"time"
+
+	"github.com/dengsgo/math-engine/engine"
 )
 
 func main() {
@@ -15,6 +16,9 @@ func main() {
 
 // input loop
 func loop() {
+	engine.RegFunction("double", 1, func(expr ...engine.ExprAST) float64 {
+		return engine.ExprASTResult(expr[0]) * 2
+	})
 	for {
 		fmt.Print("input /> ")
 		f := bufio.NewReader(os.Stdin)