Marquee-aware string interpolation

If you want to create your markdown programmatically you'd probably want to use some sort of string interpolation such as glue(). However, the custom span syntax of marquee interferes with the standard interpolation syntax of glue. This function let's you use both together.

Usage

marquee_glue(
  ...,
  .sep = "",
  .envir = parent.frame(),
  .open = "{",
  .close = "}",
  .na = "NA",
  .null = character(),
  .comment = character(),
  .literal = FALSE,
  .transformer = NULL,
  .trim = TRUE
)

marquee_glue_data(
  .x,
  ...,
  .sep = "",
  .envir = parent.frame(),
  .open = "{",
  .close = "}",
  .na = "NA",
  .null = character(),
  .comment = character(),
  .literal = FALSE,
  .transformer = NULL,
  .trim = TRUE
)

Arguments

...

[expressions]
Unnamed arguments are taken to be expression string(s) to format. Multiple inputs are concatenated together before formatting. Named arguments are taken to be temporary variables available for substitution.

For `glue_data()`, elements in `...` override the values in `.x`.

.sep

[character(1): ‘""’]
Separator used to separate elements.

.envir

[environment: parent.frame()]
Environment to evaluate each expression in. Expressions are evaluated from left to right. If .x is an environment, the expressions are evaluated in that environment and .envir is ignored. If NULL is passed, it is equivalent to emptyenv().

.open

[character(1): ‘\{’]
The opening delimiter. Doubling the full delimiter escapes it.

.close

[character(1): ‘\}’]
The closing delimiter. Doubling the full delimiter escapes it.

.na

[character(1): ‘NA’]
Value to replace NA values with. If NULL missing values are propagated, that is an NA result will cause NA output. Otherwise the value is replaced by the value of .na.

.null

[character(1): ‘character()’]
Value to replace NULL values with. If character() whole output is character(). If NULL all NULL values are dropped (as in paste0()). Otherwise the value is replaced by the value of .null.

.comment

[character(1): ‘#’]
Value to use as the comment character.

.literal

[boolean(1): ‘FALSE’]
Whether to treat single or double quotes, backticks, and comments as regular characters (vs. as syntactic elements), when parsing the expression string. Setting .literal = TRUE probably only makes sense in combination with a custom .transformer, as is the case with glue_col(). Regard this argument (especially, its name) as experimental.

.transformer

[function]
A function taking two arguments, text and envir, where text is the unparsed string inside the glue block and envir is the execution environment. A .transformer lets you modify a glue block before, during, or after evaluation, allowing you to create your own custom glue()-like functions. See vignette("transformers") for examples.

.trim

[logical(1): ‘TRUE’]
Whether to trim the input template with trim() or not.

.x

[listish]
An environment, list, or data frame used to lookup values.

Value

A character vector

Details

If you choose a different set of delimiters than "{" and "}" for the interpolation the functions will call the equivalent glue functions directly. However, if you keep the defaults, the functions will use a custom transformer that will make sure to keep the marquee custom span notation. You can both interpolate the content of the span, as well as the span class (see examples)

Examples

# standard use
red_text <- "this text will be red"
marquee_glue("This will be black and {.red {red_text}}!")
#> This will be black and {.red this text will be red}!

# if the span is not valid it will be treated as standard glue interpolation
try(
  marquee_glue("This will be black and {.red}!")
)
#> Error : Failed to evaluate glue component {.red}
#> Caused by error:
#> ! object '.red' not found

# You can interpolate the tag name as well
col <- "green"
marquee_glue("This will be black and {.{col} this text will be {col}}!")
#> This will be black and {.green this text will be green}!

# Tag name interpolation must follow a `.` or a `#` as these identify the
# bracket pair as a custom span class
col <- ".yellow"
# This is not what you want probably
marquee_glue("This will be black and {{col} this text will be {col}}!")
#> This will be black and {col} this text will be .yellow}!

# Tag interpolation should also interpolate the full tag and be followed by
# a space in order to be valid
part <- "l"
marquee_glue("This will be black and {.ye{part}low this text will be {col}}!")
#> This will be black and {.ye{part}low this text will be .yellow}!
try(
  marquee_glue("This will be black and {.{part}avender this text will be {col}}!")
)
#> Error in .transformer(expr, env) : 
#>   Malformed marquee interpolation block. When interpolating a tag
#> name it must be followed by a space