表达式

表达式的定义

type Expr interface {
    Node
    // contains filtered or unexported methods
}
type BadExpr struct{ ... }
type BinaryExpr struct{ ... }
type CallExpr struct{ ... }
type Expr interface{ ... }
type ExprStmt struct{ ... }
type IndexExpr struct{ ... }
type KeyValueExpr struct{ ... }
type ParenExpr struct{ ... }
type SelectorExpr struct{ ... }
type SliceExpr struct{ ... }
type StarExpr struct{ ... }
type TypeAssertExpr struct{ ... }
type UnaryExpr struct{ ... }

我们以ast.BinaryExpr表达的二元算术表达式开始，因为加减乘除四则运算是我们最熟悉的表达式结构：

func main() {
    expr, _ := parser.ParseExpr(`1+2*3`)
    ast.Print(nil, expr)
}
-------------------------------output-------------------------------
 0  *ast.BinaryExpr {
 1  .  X: *ast.BasicLit {
 2  .  .  ValuePos: 1
 3  .  .  Kind: INT
 4  .  .  Value: "1"
 5  .  }
 6  .  OpPos: 2
 7  .  Op: +
 8  .  Y: *ast.BinaryExpr {
 9  .  .  X: *ast.BasicLit {
10  .  .  .  ValuePos: 3
11  .  .  .  Kind: INT
12  .  .  .  Value: "2"
13  .  .  }
14  .  .  OpPos: 4
15  .  .  Op: *
16  .  .  Y: *ast.BasicLit {
17  .  .  .  ValuePos: 5
18  .  .  .  Kind: INT
19  .  .  .  Value: "3"
20  .  .  }
21  .  }
22  }