Make a pattern optional

Specifies that the preceding pattern should occur zero or one time. Equivalent to the ? quantifier.

xp_op_optional(pattern)

Arguments

pattern

A regexpert object or character string from the pipe.

Value

A regexpert object.

Examples

# Match "color" or "colour"
xp_build_literal("colo") %>% 
  xp_build_literal("u") %>% 
  xp_op_optional() %>% 
  xp_build_literal("r")
#> <regexpert pattern>
#>   (?:colou)?r

# Optional area code
xp_build_literal("(") %>% xp_build_digits() %>% xp_op_repeat(3) %>% 
  xp_build_literal(") ") %>% 
  xp_op_optional() %>% 
  xp_build_digits() %>% xp_op_repeat(7)
#> <regexpert pattern>
#>   (?:(?:(?:(\d){3}) )?\d){7}