r - R 中干净、简单的函数工厂

Question

简短的例子。 我正在通过使用不同的“规范”对其进行测试来探索函数的行为，f(spec) .我手写了一个规范，spec1 ，并且正在创建新规范作为其变体。为此，我决定编写一个函数:

spec1 = list(fy = list(a = 1), fx = list(f1 = function(x) 10-x, f2 = function(x) 2-x))

make_spec = function(f = function(x) 10-x, xtheta = 2)
    list(fy = list(a = 1), fx = list(f1 = f, f2 = function(x) xtheta-x))

res1 = make_spec()

# first problem: they don't match

    all.equal(res1,spec1)
    # [1] "Component “fx”: Component “f2”: target, current do not match when deparsed"
    # ^ this happens, even though...
    res1$fx$f2(4) == spec1$fx$f2(4)
    # TRUE

# second problem: res1 is fugly

    res1
    # $fy
    # $fy$a
    # [1] 1
    # 
    # 
    # $fx
    # $fx$f1
    # function (x) 
    # 10 - x
    # <environment: 0x000000000f8f2e20>
    # 
    # $fx$f2
    # function (x) 
    # xtheta - x
    # <environment: 0x000000000f8f2e20>

    str(res1)
    # even worse

我的目标 make_spec是...

all.equal(spec1, res1)和/或 identical(spec1, res1)

为 str(res1)是人类可读的(没有 <environment: ptr> 标签或 srcfilecopy)

避免 substitute和 eval如果可能的话(不是高优先级)

避免写出 substitute 的第二个参数(参见下面的“完整”示例)

是否有一种惯用的方法来实现部分或所有这些目标？

完整的例子。 我不确定上面的例子是否完全涵盖了我的用例，所以这里是后者:

spec0 = list(
    v_dist = list(
        pdf  = function(x) 1,
        cdf  = function(x) x,
        q    = function(x) x,
        supp = c(0,1)
    )
    ,
    ucondv_dist = {
        ucondv_dist = list()
        ucondv_dist$condmean    = function(v) 10-v
        ucondv_dist$pdf         = function(u,v) dnorm(u, ucondv_dist$condmean(v), 50)
        ucondv_dist$cdf         = function(u,v) pnorm(u, ucondv_dist$condmean(v), 50)
        ucondv_dist
    }
)

make_spec = function(ycondx_condmean = function(x) 10-x, ycondx_sd = 50){

  s = substitute(list(
    x_dist = list(
      pdf  = function(x) 1,
      cdf  = function(x) x,
      q  = function(x) x,
      supp = c(0,1)
    )
    ,
    ycondx_dist = {
      ycondx_dist = list()
      ycondx_dist$condmean  = ycondx_condmean
      ycondx_dist$pdf     = function(u,v) dnorm(u, ycondx_dist$condmean(v), ycondx_sd)
      ycondx_dist$cdf     = function(u,v) pnorm(u, ycondx_dist$condmean(v), ycondx_sd)
      ycondx_dist
    }
  )
  , list(ycondx_condmean=ycondx_condmean, ycondx_sd = ycondx_sd))

  eval(s, .GlobalEnv)
}

res0 = make_spec()

旁注 .我不知道“函数工厂”在这里是否合适，因为我不是计算机科学家，但它似乎相关。我只找到了 a paragraph on the concept related to R .

Answer 1

函数的封闭环境不同导致输出的差异/解析的差异。因此，要获得所需的输出，需要做两件事:

使环境相同

将封闭环境中的变量替换到函数体中。

然而，这样做你会得到你不想要的双倍剂量的评估/替代品，所以也许会有另一种选择。

make_spec <- function(f = function(x) 10-x, xtheta = 2) {
  e <- parent.frame()
  fixClosure <- function(func)
    eval(eval(substitute(substitute(func)), parent.frame()), e)

  list(fy = list(a = 1), fx = list(
    f1 = fixClosure(f), 
    f2 = fixClosure(function(x) xtheta-x)
  ))
}

spec1 <- list(fy = list(a = 1), fx = list(f1 = function(x) 10-x, f2 = function(x) 2-x))
res1 <- make_spec()

all.equal(res1, spec1)
[1] TRUE