dparse: Create R-based Dparser tree walking function based on grammar

Description

Note R-based dparser tree walking works on Windows (with R tools) Mac, or Linux. Linking to arbitrary c grammars works on any platform.

Usage

dparse(
  grammar,
  start_state = 0,
  save_parse_tree = TRUE,
  partial_parses = FALSE,
  compare_stacks = TRUE,
  commit_actions_interval = 100,
  fixup = TRUE,
  fixup_ebnf = FALSE,
  nogreedy = FALSE,
  noheight = FALSE,
  use_file_name = TRUE,
  parse_size = 1024,
  verbose_level = 0,
  children_first = TRUE,
  ...
)

Value

A function that allows parsing of a file based on the grammar supplied. This function would be able to parse arbitrary grammars the way you may want with your own user supplied function.

Arguments

grammar: Dparser grammar filename (must be a file with a ".g" extension)
start_state: Start State (default 0)
save_parse_tree: Save Parse Tree (default TRUE)
partial_parses: Partial Parses (default FALSE)
compare_stacks: Compare Stacks (default TRUE)
commit_actions_interval: Commit Interval (default 100)
fixup: Fix-up Internal Productions (default FALSE)
fixup_ebnf: Fixup EBNF Productions (default FALSE)
nogreedy: No Greediness for Disambiguation (default FALSE)
noheight: No Height for Disambiguation (default FALSE)
use_file_name: Use File Name for syntax errors (default TRUE)
parse_size: Parser size (default 1024)
verbose_level: the level of verbosity when creating parser (default 0)
children_first: When TRUE, parse the children before the parent (default TRUE).
...: Parameters sent to mkdparse, with the exception of use_r_header which is forced to be TRUE.

Garbage collection

There are two user options that control if the dlls for the grammars created by dparser will be deleted upon garbage collection or R exit if they are not associated with any active objects. These are:

dpaser.rm.unnamed.parser.dll:: when TRUE, this remove parsers that are created from strings, or other memory-based items in R.
dpaser.rm.unnamed.parser.dll:: when TRUE, this removes parsers created from grammar files.

Examples

Run this code

# \donttest{
## This creates the R based parsing function.  It requires
## compilation and runs on most OSes, with the exception of solaris.
## Windows requires Rtools to be installed.
f <- dparse(system.file("tran.g", package = "dparser"),children_first=FALSE)

## Once created, you may then use this function to parse an
## arbitrary syntax file.  For example:
f("
b       = -1
d/dt(X) = a*X + Y*Z;
d/dt(Y) = b*(Y - Z);
d/dt(Z) = -X*Y + c*Y - Z
if (t < 0.02 | t > 99.98){
    print
}
", function(name, value, pos, depth){
    ## This prints the name, value, position and depth passed to the
    ##parsing function.
    cat(sprintf("name:%s;value:%s;pos:%s;depth:%s\n", name, value, pos,
                 depth));
})

## You could use a better R parsing function; You could also use
## this as a starting place for your own C-based parser
# }