locbalpar2 {lazy.tools}

R Documentation

Return the locations of the matching parentheses

Description

Return the locations of the matching parentheses

Usage

locbalpar2(expr, loc)

Arguments

loc	The starting or ending locations of the parentheses in expr whose matching pairs will be found.
epr	Input string vector.

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 paren in the line.

Examples

# When counting characters, count the length 0 character as 1.
# For example, consider the example below where
# expr1 has length 0 characters at lines 2 and 4 and
# expr2 has length 1 blank characters at lines 2 and 4.
# The locations of parems must be counted from expr2, not expr1.
expr1 <- c( "1(", "", "4)(", "", "89)" )
expr2 <- c( "1(", " ", "4)(", " ", "89)" )
cat("    1234567890123456789012345678901234567890\n")
num <- paste(1:length(expr1),": ", sep="")
cat(" "); cat(paste(num, expr1, ": ", nchar(expr1), "\n", sep=""))
cat("    1234567890123456789012345678901234567890\n")
num <- paste(1:length(expr2),": ", sep="")
cat(" "); cat(paste(num, expr2, ": ", nchar(expr2), "\n", sep=""))
exprc1 <- unlist(strsplit(expr1,""))
exprc2 <- unlist(strsplit(expr2,""))
Print(1:length(exprc2),exprc1, exprc2)
locbalpar2( expr1, c(2,5,6,10) )
locbalpar2( expr2, c(2,5,6,10) )
exprc1 <- unlist(strsplit(expr1,""))
exprc2 <- unlist(strsplit(expr2,""))
Print(1:length(exprc2),exprc1, exprc2)
locbalpar2( expr1, c(2,5,6,10) )
locbalpar2( expr2, c(2,5,6,10) )


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"
)

cat("    1234567890123456789012345678901234567890\n")
cat(" "); cat(paste(paste(1:length(expr),": ", sep=""), expr,"\n", sep=""))

locbalpar2( expr, c(23,36, 184) )

#
# e1 <- unlist(strsplit(expr,""))
# expr2 <- sub("^$"," ",expr)
# e2 <- unlist(strsplit(expr2,""))
# Print(1:199, e1, e2)

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