如何使用大包进行链式操作？

Question

For example, if I want to perform r = a * (b - c). I would do:

var r, a, b, c, t big.Int

t.Sub(&b, &c)
r.Mul(&a, &t)

In package documentation, it says that operations return result to allow chaining. But since the used variable isn't used as operator argument, but only to store result, how can I chain operations? In other words, how could I write my exemple using only one line of code, without temporary variable t?

Answer 1

For example, on Go 1,

package main

import (
    "fmt"
    "math/big"
)

func main() {
    var r, a, b, c big.Int
    a = *big.NewInt(7)
    b = *big.NewInt(42)
    c = *big.NewInt(24)

    // r = a * (b - c)
    r.Mul(&a, r.Sub(&b, &c))

    fmt.Println(r.String())
}

Output:

126