Customization of the highr package

Customization of the highr package

If you are not satisfied with the default syntax highlighting commands in the highr package, you can just use your own tags/commands. In this vignette, we show a brief example.

The default highlighting commands are stored in two internal data frames cmd_latex and cmd_html:

library(highr)
highr:::cmd_latex
##                          cmd1 cmd2
## COMMENT              \\hlcom{    }
## DEFAULT              \\hldef{    }
## FUNCTION             \\hlkwa{    }
## IF                   \\hlkwa{    }
## ELSE                 \\hlkwa{    }
## WHILE                \\hlkwa{    }
## FOR                  \\hlkwa{    }
## IN                   \\hlkwa{    }
## BREAK                \\hlkwa{    }
## REPEAT               \\hlkwa{    }
## NEXT                 \\hlkwa{    }
## NULL_CONST           \\hlkwa{    }
## LEFT_ASSIGN          \\hlkwb{    }
## EQ_ASSIGN            \\hlkwb{    }
## RIGHT_ASSIGN         \\hlkwb{    }
## SYMBOL_FORMALS       \\hlkwc{    }
## SYMBOL_SUB           \\hlkwc{    }
## SLOT                 \\hlkwc{    }
## SYMBOL_FUNCTION_CALL \\hlkwd{    }
## NUM_CONST            \\hlnum{    }
## '+'                  \\hlopt{    }
## '-'                  \\hlopt{    }
## '*'                  \\hlopt{    }
## '/'                  \\hlopt{    }
## '^'                  \\hlopt{    }
## '$'                  \\hlopt{    }
## '@'                  \\hlopt{    }
## ':'                  \\hlopt{    }
## '?'                  \\hlopt{    }
## '~'                  \\hlopt{    }
## '!'                  \\hlopt{    }
## SPECIAL              \\hlopt{    }
## GT                   \\hlopt{    }
## GE                   \\hlopt{    }
## LT                   \\hlopt{    }
## LE                   \\hlopt{    }
## EQ                   \\hlopt{    }
## NE                   \\hlopt{    }
## AND                  \\hlopt{    }
## AND2                 \\hlopt{    }
## OR                   \\hlopt{    }
## OR2                  \\hlopt{    }
## NS_GET               \\hlopt{    }
## NS_GET_INT           \\hlopt{    }
## STR_CONST            \\hlsng{    }

This data frame is passed to the markup argument in hilight(), so we are free to pass a modified version there. Suppose I want to use the command \my<*> instead of \hl<*>:

m = highr:::cmd_latex
m[, 1] = sub('\\hl', '\\my', m[, 1], fixed = TRUE)
head(m)
##              cmd1 cmd2
## COMMENT  \\mycom{    }
## DEFAULT  \\mydef{    }
## FUNCTION \\mykwa{    }
## IF       \\mykwa{    }
## ELSE     \\mykwa{    }
## WHILE    \\mykwa{    }

Then

hilight("x = 1+1  # a comment")  # default markup
## [1] "\\hldef{x} \\hlkwb{=} \\hlnum{1}\\hlopt{+}\\hlnum{1}  \\hlcom{# a comment}"
hilight("x = 1+1  # a comment", markup = m)  # custom markup
## [1] "\\mydef{x} \\mykwb{=} \\mynum{1}\\myopt{+}\\mynum{1}  \\mycom{# a comment}"

This allows one to use arbitrary commands around the text symbols in the R code. See https://github.com/yihui/highr/blob/master/R/highlight.R for how cmd_latex and cmd_html were generated in highr.

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