Convert "Regex" to typst

src/Warm-Ups/Regex/main.typ

@@ -0,0 +1,135 @@
+#import "@local/handout:0.1.0": *
+
+#show: handout.with(
+  title: [The Regex Warm-Up],
+  by: "Mark",
+)
+
+
+Last time, we discussed Deterministic Finite Automata. One interesting application of these mathematical objects is found in computer science: Regular Expressions. \
+This is often abbreviated "regex," which is pronounced like "gif."
+
+#v(2mm)
+
+Regex is a language used to specify patterns in a string. You can think of it as a concise way to define a DFA, using text instead of a huge graph. \
+
+Often enough, a clever regex pattern can do the work of a few hundred lines of code.
+
+#v(2mm)
+
+Like the DFAs we've studied, a regex pattern _accepts_ or _rejects_ a string. However, we don't usually use this terminology with regex, and instead say that a string _matches_ or _doesn't match_ a pattern.
+
+#v(5mm)
+
+Regex strings consist of characters, quantifiers, sets, and groups.
+
+#v(5mm)
+
+
+
+*Quantifiers* \
+Quantifiers specify how many of a character to match. \
+There are four of these: `+`, `*`, `?`, and `{ }`.
+
+#v(4mm)
+
+`+` means "match one or more of the preceding token" \
+`*` means "match zero or more of the preceding token"
+
+For example, the pattern `ca+t` will match the following strings:
+- `cat`
+- `caat`
+- `caaaaaaaat`
+`ca+t` will *not* match the string `ct`. \
+The pattern `ca*t` will match all the strings above, including `ct`.
+
+
+#v(4mm)
+
+
+`?` means "match one or none of the preceding token" \
+The pattern `linea?r` will match only `linear` and `liner`.
+
+#v(4mm)
+
+Brackets `{min, max}` are the most flexible quantifier. \
+They specify exactly how many tokens to match: \
+`ab{2}a` will match only `abba`. \
+`ab{1,3}a` will match only `aba`, `abba`, and `abbba`. \
+`ab{2,}a` will match any `ab...ba` with at least two `b`s. // spell:disable-line
+
+#problem()
+Write the patterns `a*` and `a+` using only `{ }`.
+#v(1fr)
+
+#problem()
+Draw a DFA equivalent to the regex pattern `01*0`.
+#v(1fr)
+
+#pagebreak()
+
+
+
+
+
+
+*Characters, Sets, and Groups* \
+In the previous section, we saw how we can specify characters literally: \
+`a+` means "one or more `a` characters" \
+There are, of course, other ways we can specify characters.
+
+#v(4mm)
+
+The first such way is the _set_, denoted `[ ]`. A set can pretend to be any character inside it. \
+For example, `m[aoy]th` will match `math`, `moth`, or `myth`. \
+`a[01]+b` will match `a0b`, `a111b`, `a1100110b`, and any other similar string. \
+
+#v(4mm)
+
+We can negate a set with a `^`. \
+`[^abc]` will match any single character except `a`, `b`, or `c`, including symbols and spaces.
+
+#v(4mm)
+
+If we want to keep characters together, we can use the _group_, denoted `( )`. \
+
+Groups work exactly as you'd expect, representing an atomic#footnote([In other words, "unbreakable"]) group of characters. \
+`a(01)+b` will match `a01b` and `a010101b`, but will *not* match `a0b`, `a1b`, or `a1100110b`.
+
+#problem()
+You are now familiar with most of the tools regex has to offer. \
+Write patterns that match the following strings:
+
+- An ISO-8601 date, like `2022-10-29`. \
+  #hint([Invalid dates like `2022-13-29` should also be matched.])
+
+- An email address. \
+  #hint([Don't forget about subdomains, like `math.ucla.edu`.])
+
+- A UCLA room number, like `MS 5118` or `Kinsey 1220B`.
+
+- Any ISBN-10 of the form `0-316-00395-7`. \
+  #hint([Remember that the check digit may be an `X`. Dashes are optional.])
+
+- A word of even length. \
+  #hint([
+    The set `[A-z]` contains every english letter, capitalized and lowercase. \
+    `[a-z]` will only match lowercase letters.
+  ])
+
+- A word with exactly 3 vowels. \
+  #hint([
+    The special token `\w` will match any word character. \
+    It is equivalent to `[A-z0-9_]`. `_` represents a literal underscore.
+  ])
+
+- A word that has even length and exactly 3 vowels.
+
+- A sentence that does not start with a capital letter.
+#v(1fr)
+
+#problem()
+If you'd like to know more, check out `https://regexr.com`.
+It offers an interactive regex prompt,
+as well as a cheatsheet that explains every other regex token there is. \
+You can find a nice set of challenges at `https://alf.nu/RegexGolf`.