Return the locations of the matching parentheses

Description

Return the locations of the matching parentheses

Usage

locbalpar2(expr, loc, debug = 0)

Arguments

Details

This is a expanded version of lazy.tools:locbalpar which can handle a string vector input.

When expr is a scalar string, use lazy.tools:locbalpar.

loc must be positive and less than sum(nchar(exp)).
substring(exp,loc,loc) must be opening or closing parens.
Otherwise, this function returns line=0, locbp=0.

The following characters are treated as parentheses:
"(", "{", "[", "<", ")", "}", "]", ">"

Value

A list of
line the line number.
locbp the locations of matching parens in the line.

Examples

# When counting characters, count the length 0 character, "", as 0.
# For example, consider the example below where
# expr1 has length 0 character, "", at lines 2 and 4 and
# expr2 has length 1 blank character, " ",  at lines 2 and 4.
# The locations of parens must be counted from exprc1 and exprc2.
# The two results below should be the same.
expr1 <- c( "1(", "", "4)(", "", "89)" )
expr2 <- c( "1(", " ", "4)(", " ", "89)" )
Printm( expr1, expr2 )
exprc1 <- unlist(strsplit(expr1,""))
exprc2 <- unlist(strsplit(expr2,""))
Printm( exprc1, exprc2 )
locbalpar2( expr1, c(2,5,4) )
locbalpar2( expr2, c(2,6,5) )


# Find the matching closing brace.
expr <- c(
"locbalpar2 <- function( expr, loc ){",
" # find the location of the balanced paren",
" # use standard version when expr is a string",
"",
" if( !is.vector(expr) ){",
"  return( locbalpar( expr, loc ) )",
" }",
"",
"} # locbalpar2"
)

locbalpar2( expr, regexpr("{", expr, fixed=1 )[1] )