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Mention character class instead of escaping

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@jennybc
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Hadley Wickham
2022-11-09 14:37:55 -06:00
parent 899c1dce85
commit 4a761c77c6
1 changed files with 9 additions and 0 deletions
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regexps.qmd
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@@ -350,6 +350,14 @@ That lets you to avoid one layer of escaping:
str_view(x, r"{\\}") str_view(x, r"{\\}")
``` ```
If you're trying to match a literal `.`, `$`, `|`, `*`, `+`, `?`, `{`, `}`, `(`, `)`, there's an alternative to using a backslash escape: you can use a character class: `[.]`, `[$]`, `[|]`, \...
all match the literal values.
```{r}
str_view(c("abc", "a.c", "a*c", "a c"), "a[.]c")
str_view(c("abc", "a.c", "a*c", "a c"), ".[*]c")
```
The full set of metacharacters is `.^$\|*+?{}[]()`. The full set of metacharacters is `.^$\|*+?{}[]()`.
In general, look at punctuation characters with suspicion; if your regular expression isn't matching what you think it should, check if you've used any of these characters. In general, look at punctuation characters with suspicion; if your regular expression isn't matching what you think it should, check if you've used any of these characters.
@@ -885,3 +893,4 @@ You'll find stringi very easy to pick up because it follows many of the the same
In the next chapter, we'll talk about a data structure closely related to strings: factors. In the next chapter, we'll talk about a data structure closely related to strings: factors.
Factors are used to represent categorical data in R, data where there is a fixed and known set of possible values identified by a vector of strings. Factors are used to represent categorical data in R, data where there is a fixed and known set of possible values identified by a vector of strings.