[R] separate commands by semicolon

[Adrian Dușa]

Oh yes, completely forgot about partial parsing. One possible (quick)
solution:

txt <- "print(2); bar <- \"don't ; use semicolons\"; foo <- '3;4'; ls("
sf <- srcfile("txt")
tryit <- tryCatch(parse(text = txt, srcfile = sf), error = identity)
gpd <- getParseData(sf)
pos <- c(0, gpd$col1[gpd$token == "';'"], nchar(txt) + 1)
final <- c()
for (i in seq(length(pos) - 1)) {
    final <- c(final, substr(txt, pos[i] + 1, pos[i + 1] - 1))
}

Which outputs:
[1] "print(2)"                           " bar <- \"don't ; use
semicolons\""
[3] " foo <- '3;4'"                      " ls("

Excellent, thanks very much,
Adrian



On Mon, Sep 19, 2016 at 3:19 PM, Duncan Murdoch <murdoch.duncan at gmail.com>
wrote:

> On 19/09/2016 7:59 AM, Adrian Dușa wrote:
>
>> On Sun, Sep 18, 2016 at 12:34 AM, Peter Langfelder <
>> peter.langfelder at gmail.com> wrote:
>>
>> > On Sat, Sep 17, 2016 at 2:12 PM, David Winsemius <
>> dwinsemius at comcast.net>
>> > wrote:
>> > > Not entirely clear. If you were intending to just get character output
>> > then you could just use:
>> > >
>> > > strsplit(txt, ";")
>> >
>> > You would want to avoid splitting within character strings
>> > (print(";")) and in comments (print(2); ls() # This prints 2; then
>> > lists...) The comment char could also appear in a character string,
>> > where it does not mean the start of a comment...
>>
>>
>> Yes, that would be the problem.
>> Returning to my original post, modifying the example:
>>
>> x <- "print(2); bar <- \"don't ; use semicolons\"; foo <- '3;4'; ls("
>>
>> This should result in a character vector of length 4:
>> [1] "print(2)"                          "bar <- \"don't ; use
>> semicolons\""
>> [3] "foo <- '3;4'"                      "ls("
>>
>> even though the last command would cause an error using parse(text = x)
>>
>> Perhaps this is not that important (I am trying to simulate a normal R
>> console), and parse only if it syntactically correct.
>> I was merely curious if this could be done, likely using regular
>> expressions (surely strsplit doesn't solve it).
>>
>> Best,
>> Adrian
>>
>> See the section on "partial parsing" in the ?parse help page.
>
> Duncan Murdoch
>
>


-- 
Adrian Dusa
University of Bucharest
Romanian Social Data Archive
Soseaua Panduri nr.90
050663 Bucharest sector 5
Romania

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