Julia 宏可能会以不同的方式对待变量和文字吗？

Question

各位 Julia 用户，大家好，

为什么会这样

using HDF5, JLD
  s = "It would take me 48 hours to recompute this."
  filename_no_ext = "eric_demo_file"
  @save filename_no_ext
  readdir()
  @load "eric_demo_file"

评估与此不同？

using HDF5, JLD
  s = "It would take me 48 hours to recompute this."
  filename_no_ext = "eric_demo_file"
  @save filename_no_ext
  readdir()
  @load filename_no_ext

Answer 1

与函数相比，宏是非常不同的野兽。区别之一是他们不评估他们的论点:http://docs.julialang.org/en/latest/manual/metaprogramming/#macro-invocation

It is important to emphasize that macros receive their arguments as expressions, literals, or symbols.

要了解比较 2 个输出的含义(留作练习):

julia> macroexpand(:(@load filename_no_ext))

julia> macroexpand(:(@load "eric_demo_file"))