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Isn't the rather big flexibility of R to not eagerly evaluate, or to rewrite function arguments entirely (and apparently scope manipulation, that's a new one fo

by nyir 12y ago

Isn't the rather big flexibility of R to not eagerly evaluate, or to rewrite function arguments entirely (and apparently scope manipulation, that's a new one for me) one of the major points of critic? It always seemed to me that having "proper" macros is a selling point rather than only an approximation/emulation.

johnmyleswhite 12y ago
I fully share that viewpoint, but there are many R users who believe that R's idiosyncratic evaluation rules are essential to writing "readable" code.
- stewbrew 12y ago
  They sometimes allow to write functions for which you would have to use macros in other languages.
jacobolus 12y ago
> Isn't the rather big flexibility of R to not eagerly evaluate, or to rewrite function arguments entirely (and apparently scope manipulation, that's a new one for me) one of the major points of critic [sic]? For anyone coming from a programming background, the way R deals with scope and function arguments is incredibly confusing and frustrating, and causes all kinds of nasty bugs. It seems pathological. For several of the academic statisticians I’ve talked to though, R seems to be their first programming language, and they learn (in a slightly fuzzy way, but enough to do their work) the behavior of its APIs without thinking too deeply about issues of scope or eager vs. lazy argument evaluation, etc. However it works is “just the way it is.” When their expectations about what it should do are violated, they futz with the code until it starts working again and call it a day. People are typically using R to solve narrow concrete problems instead of building systems out of it, so most end-users don’t really have practice with thinking about API design. (R is similar to Matlab in this way.) Personally I think many of R’s idioms are net negative for the language because they make the abstractions much less simple/clean, and make it more difficult to solve problems in general/adaptable ways. But for someone who already has substantial amounts of time invested in learning R’s API quirks, and doesn’t know any other way, it might not seem like a big deal.
- johnmyleswhite 12y ago
  A fun test to see if R users understand how R works is to ask them to predict the behavior of the following snippet of code: foo <- function(a, b) { if (a == 0) { return(1) } else { return(2) } } foo(0, stop("Error!")) foo(1, stop("Error!"))
  - Hansi 12y ago
    Why? Seems to simple. I normally go straight for drop=FALSE the most evil default issue of the language.
    - jghn 12y ago
      Agreed. There are many WTF things I can think of in R, this is absolutely not one of them.
      - johnmyleswhite 12y ago
        My experience asking people about that snippet is that very few people can correctly predict the results of that function without actually executing the code. What interests me about the question is that many people's mental model of how R programs are evaluated is often too vague to enable them to produce sharp predictions about program behavior prior to executing code.
        RA_Fisher 12y ago
        This is funny because I was heavily skeptical yet completely reversed my opinion within 10 minutes. I correctly predicted the results, but I program R professionally. Then I asked my partner who's a non-programmer to read the snippet and her prediction was that the program would stop. That led me to reflect back on your statement. I think the key word is "sharp". I correctly predicted the result, but that's only because I trust lazy-eval heavily. Even then, it's hard to really cement trust in lazy-eval (for me) as it's difficult to mentally map. That's not exactly sharp after all!

by nyir 12y ago

johnmyleswhite 12y ago

I fully share that viewpoint, but there are many R users who believe that R's idiosyncratic evaluation rules are essential to writing "readable" code.

stewbrew 12y ago
They sometimes allow to write functions for which you would have to use macros in other languages.

jacobolus 12y ago

> Isn't the rather big flexibility of R to not eagerly evaluate, or to rewrite function arguments entirely (and apparently scope manipulation, that's a new one for me) one of the major points of critic [sic]? For anyone coming from a programming background, the way R deals with scope and function arguments is incredibly confusing and frustrating, and causes all kinds of nasty bugs. It seems pathological. For several of the academic statisticians I’ve talked to though, R seems to be their first programming language, and they learn (in a slightly fuzzy way, but enough to do their work) the behavior of its APIs without thinking too deeply about issues of scope or eager vs. lazy argument evaluation, etc. However it works is “just the way it is.” When their expectations about what it should do are violated, they futz with the code until it starts working again and call it a day. People are typically using R to solve narrow concrete problems instead of building systems out of it, so most end-users don’t really have practice with thinking about API design. (R is similar to Matlab in this way.) Personally I think many of R’s idioms are net negative for the language because they make the abstractions much less simple/clean, and make it more difficult to solve problems in general/adaptable ways. But for someone who already has substantial amounts of time invested in learning R’s API quirks, and doesn’t know any other way, it might not seem like a big deal.

johnmyleswhite 12y ago
A fun test to see if R users understand how R works is to ask them to predict the behavior of the following snippet of code: foo <- function(a, b) { if (a == 0) { return(1) } else { return(2) } } foo(0, stop("Error!")) foo(1, stop("Error!"))
- Hansi 12y ago
  Why? Seems to simple. I normally go straight for drop=FALSE the most evil default issue of the language.
  - jghn 12y ago
    Agreed. There are many WTF things I can think of in R, this is absolutely not one of them.
    - johnmyleswhite 12y ago
      My experience asking people about that snippet is that very few people can correctly predict the results of that function without actually executing the code. What interests me about the question is that many people's mental model of how R programs are evaluated is often too vague to enable them to produce sharp predictions about program behavior prior to executing code.
      - RA_Fisher 12y ago
        This is funny because I was heavily skeptical yet completely reversed my opinion within 10 minutes. I correctly predicted the results, but I program R professionally. Then I asked my partner who's a non-programmer to read the snippet and her prediction was that the program would stop. That led me to reflect back on your statement. I think the key word is "sharp". I correctly predicted the result, but that's only because I trust lazy-eval heavily. Even then, it's hard to really cement trust in lazy-eval (for me) as it's difficult to mentally map. That's not exactly sharp after all!