the function call procedure now check the number of actual parameters against the numer of formal parameters

operand-func.go

@@ -6,6 +6,7 @@ package expr
 
 import (
 	"errors"
+	"fmt"
 )
 
 // -------- function call term
@@ -21,6 +22,20 @@ func newFuncCallTerm(tk *Token, args []*term) *term {
 }
 
 // -------- eval func call
+func checkFunctionCall(ctx ExprContext, name string, params []any) (err error) {
+	if info, exists := ctx.GetFuncInfo(name); exists {
+		if info.MinArgs() > len(params) {
+			err = fmt.Errorf("too few params -- expected %d, got %d", info.MinArgs(), len(params))
+		}
+		if info.MaxArgs() >= 0 && info.MaxArgs() < len(params) {
+			err = fmt.Errorf("too much params -- expected %d, got %d", info.MaxArgs(), len(params))
+		}
+	} else {
+		err = fmt.Errorf("unknown function %s()", name)
+	}
+	return
+}
+
 func evalFuncCall(parentCtx ExprContext, self *term) (v any, err error) {
 	ctx := cloneContext(parentCtx)
 	name, _ := self.tk.Value.(string)
@@ -34,8 +49,10 @@ func evalFuncCall(parentCtx ExprContext, self *term) (v any, err error) {
 		params[i] = param
 	}
 	if err == nil {
-		if v, err = ctx.Call(name, params); err == nil {
-			exportObjects(parentCtx, ctx)
+		if err = checkFunctionCall(ctx, name, params); err == nil {
+			if v, err = ctx.Call(name, params); err == nil {
+				exportObjects(parentCtx, ctx)
+			}
 		}
 	}
 	return
@@ -44,9 +61,9 @@ func evalFuncCall(parentCtx ExprContext, self *term) (v any, err error) {
 // -------- function definition term
 func newFuncDefTerm(tk *Token, args []*term) *term {
 	return &term{
-		tk:       *tk,
+		tk:       *tk, // value is the expression body
 		parent:   nil,
-		children: args, // arg[0]=formal-param-list, arg[1]=*ast
+		children: args, // function params
 		position: posLeaf,
 		priority: priValue,
 		evalFunc: evalFuncDef,