hilight: Syntax highlight an R code fragment

Description

This function parses the R code, fetches the tokens in it (getParseData), and attach syntax highlighting commands onto them. With proper style definitions for these commands (such as colors or font styles), the R code will be syntax highlighted in the LaTeX/HTML output. The two functions hi_latex and hi_html are wrappers of hilight for LaTeX and HTML output, respectively.

Usage

hilight(code, format = c("latex", "html"), markup, prompt = FALSE, fallback = FALSE)
hi_latex(code, ...)
hi_html(code, ...)

Arguments

code

a character string (the R source code)

format

the output format

markup

a data frame of two columns containing the markup commands

prompt

whether to add prompts to the code

fallback

whether to use the fallback method, i.e. the regular expression based method; this method is not precise and only highlights a few types of symbols such as comments, strings and functions; fallback will be set to TRUE when the input code fails to be parsed

...

arguments to be passed to hilight()

Value

A character vector for the syntax highlighted code.

Details

For the markup data frame, the first column is put before the R tokens, and the second column is behind; the row names of the data frame must be the R token names; a special row is named STANDARD, which contains the markup for the standard tokens (i.e. those that do not need to be highlighted); if missing, the built-in data frames highr:::cmd_latex and highr:::cmd_html will be used.

This function only binds markups onto R tokens, and the real syntax highlighting must be done with style definitions, which is out of the scope of this package. It was designed to be used as the syntax highlighting infrastructure of other packages such as knitr, where the colors and font styles are properly defined in the LaTeX preamble and HTML header.

Examples

Run this code

# NOT RUN {
library(highr)
hilight("x=1 # assignment")

txt = c("a <- 1 # something", "c(y=\"world\", z=\"hello\")", "b=function(x=5) {", 
    "for(i in 1:10) {
  if (i < x) print(i) else break}}", "z@child # S4 slot", 
    "'special chars <>#$%&_{}'")
cat(hi_latex(txt), sep = "\n")
cat(hi_html(txt), sep = "\n")

# the markup data frames
highr:::cmd_latex
highr:::cmd_html
# }