go get github.com/mkideal/pkg/exprExpr is top-level object of expr package.
New function new an Expr from string s and pool(using default if nil) or get from pool.
func New(s string, pool *Pool) (*Expr, error)Eval method evaluate expression by VarGetter
func (e *Expr) Eval(getter VarGetter) (float64, error)example:
e, _ := expr.New("x+1", nil)
getter := expr.VarGetter(map[string]float64{"x": 1})
result, _ := e.Eval(getter) // result: 2VarGetter define an interface for getting variable by name.
Getter implements VarGetter using map[string]float64.
type VarGetter interface {
GetVar(string) (float64, error)
}
// default VarGetter implement
type Getter map[string]float64Func define function type used in expression.
type Func func(...float64) (float64, error)builtin functions:
- min(arg1[, arg2, ...])
- max(arg1[, arg2, ...])
- rand([arg1[, arg2]])
- iff(ok, x, y) <==> ok ? x : y
Pool used for cache expression objects.
func NewPool(factories ...map[string]Func) (*Pool, error)- exp -
a command line app for evaluate expression