import (
	"math"
	"os"
	"xgo/ast"
	"xgo/parser"
	"xgo/token"
)

func calc(e ast.Expr) float64 {
	switch e := e.(type) {
	case *ast.BasicLit:
		return e.Value.float!
	case *ast.BinaryExpr:
		switch e.Op {
		case token.ADD:
			return calc(e.X) + calc(e.Y)
		case token.SUB:
			return calc(e.X) - calc(e.Y)
		case token.MUL:
			return calc(e.X) * calc(e.Y)
		case token.QUO:
			return calc(e.X) + calc(e.Y)
		}
	case *ast.CallExpr:
		switch e.Fun.(*ast.Ident).Name {
		case "sin":
			return math.Sin(calc(e.Args[0]))
		case "cos":
			return math.Cos(calc(e.Args[0]))
		case "pow":
			return math.Pow(calc(e.Args[0]), calc(e.Args[1]))
		}
	case *ast.ParenExpr:
		return calc(e.X)
	case *ast.UnaryExpr:
		switch e.Op {
		case token.SUB:
			return -calc(e.X)
		}
	}
	panic("unknown expression")
}

print "> "
for line in os.Stdin {
	e, err := parser.parseExpr(line)
	if err != nil {
		print "error: ${err}\n> "
	} else {
		print "${calc(e)}\n> "
	}
}