r - Unexpected symbol error in parse(text = str) with hyphen after a digit

Question

I am trying to parse a character string in R. R throws an "unexpected symbol" or "unexpected end of input" exception when there is a digit followed by a hyphen in the string (please see the code). Searching and trying different ways to solve this issue didn't help. Probably some lack of knowledge in my part. Any help or advise would be highly appreciated.

> str <- "abc12-3def"
> parse(text = str)
Error in parse(text = str) : <text>:1:8: unexpected symbol
1: abc12-3def
          ^

or

> str <- "abc123-"
> parse(text = str)
Error in parse(text = str) : <text>:2:0: unexpected end of input
1: abc123-
  ^

However, following examples all work normally

> str <- "abc123def"
> parse(text = str)
expression(abc123def)

or

> str <- "abc123-def"
> parse(text = str)
expression(abc123-def)

or

> str <- "abc12-3"
> parse(text = str)
expression(abc12-3)

Thank you very much in advance!

Answer 1

You can easily reproduce the parse behavior with :

str <- "3a"
parse(text = str)

parse try to parse your str as a variable name. Or, you should give an available variable name, either it should not begin with a digit or you should put it between ``. the following works :

str <- "`3a`"
parse(text = str)

and in your example , this works also :

str <- "abc12-`3def`"
parse(text = str)

Finally for your second example , it is logic that it will not work since you don't give an available expression to parse:

str <- "abc123-"  ## this will like myvar-

if your - is just a string separator, why not to transform it to _? for example:

 parse(text=gsub('-','_',str))