Support tokenizing `.` wildcard operator.

* src/paca.mjs
  (isTransition): Add new function as an improved version of the raw
    usage of `stateTransitionOperators`, equivalent to `isAnchor()` and
    `isOperator()`.
  (operatorChars, isOperator): Add new static set `operatorChars` as
    backing data of `isOperator()`, instead of ad-hoc conditional in its
    implementation.  Also now add the `.` character as an operator by
    including it in the `operatorChars` set.
  (tokenizeRegexStep): Use the new `isTransition()` function instead of
    checking the set directly.  Also tweak ternary to fit in 80 columns.
  (PRECEDENCE): Add `.` operator with lowest precedence, as it is not
    really operating on anything, and is instead a target to be operated
    on.
* tests/paca.mjs
  (test_isTransition): Add obligatory test cases.
  (test_isOperator): Include test case for `.` wildcard operator.

2 files changed, 29 insertions, 5 deletions

diff --git a/src/paca.mjs b/src/paca.mjs
index 42c2f88..5d11b05 100644
--- a/src/paca.mjs
+++ b/src/paca.mjs
@@ -306,14 +306,16 @@ const ANCHOR_FNS = {
 };
 
 const anchors = new Set(Object.keys(ANCHOR_FNS));
-
 const isAnchor = char =>
 	anchors.has(char);
 
-const stateTransitionOperators = new Set(Object.keys(TRANSITION_FNS));
+const transitionChars = new Set(Object.keys(TRANSITION_FNS));
+const isTransition = char =>
+	transitionChars.has(char);
 
+const operatorChars = new Set([...nonConcatOperators, "(", "."]);
 const isOperator = char =>
-	nonConcatOperators.has(char) || char == "(";
+	operatorChars.has(char);
 
 const tokenizeRegexStep = chars => ({ out, state, context }, char, index) => {
 	const next = chars[index + 1];
@@ -327,7 +329,7 @@ const tokenizeRegexStep = chars => ({ out, state, context }, char, index) => {
 		);
 	}
 
-	if (stateTransitionOperators.has(char)) {
+	if (isTransition(char)) {
 		return TRANSITION_FNS[char](
 			{ out, state, context },
 			char,
@@ -349,7 +351,9 @@ const tokenizeRegexStep = chars => ({ out, state, context }, char, index) => {
 	return {
 		out: out.concat(
 			op,
-			shouldConcat(char, next) ? [{ operator: "concat" }] : [],
+			shouldConcat(char, next)
+				? [{ operator: "concat" }]
+				: [],
 		),
 		state,
 		context,
@@ -385,6 +389,7 @@ const PRECEDENCE = {
 	"concat": 2,
 	"|":      1,
 	"class":  1,
+	".":      1,
 };
 
 const shouldPush = (stack, token) =>
diff --git a/tests/paca.mjs b/tests/paca.mjs
index 134fb77..bc6e1d0 100644
--- a/tests/paca.mjs
+++ b/tests/paca.mjs
@@ -12,6 +12,7 @@ import {
 	TRANSITION_FNS,
 	ANCHOR_FNS,
 	isAnchor,
+	isTransition,
 	isOperator,
 	tokenizeRegexStep,
 	tokenizeRegexFn,
@@ -618,6 +619,22 @@ const test_isAnchor = t => {
 	});
 };
 
+const test_isTransition = t => {
+	t.start("isTransition()");
+
+	t.testing("transition chars are true", () => {
+		t.assertEq(isTransition("\\"), true);
+		t.assertEq(isTransition("["),  true);
+		t.assertEq(isTransition("{"),  true);
+	});
+
+	t.testing("false for everything else", () => {
+		t.assertEq(isTransition("."), false);
+		t.assertEq(isTransition("*"), false);
+		t.assertEq(isTransition("a"), false);
+	});
+};
+
 const test_isOperator = t => {
 	t.start("isOperator()");
 
@@ -628,6 +645,7 @@ const test_isOperator = t => {
 		t.assertEq(isOperator("?"), true);
 		t.assertEq(isOperator("("), true);
 		t.assertEq(isOperator(")"), true);
+		t.assertEq(isOperator("."), true);
 	});
 
 	t.testing("false for everyday non-meta chars", () => {
@@ -3030,6 +3048,7 @@ runTests([
 	test_TRANSITION_FNS,
 	test_ANCHOR_FNS,
 	test_isAnchor,
+	test_isTransition,
 	test_isOperator,
 	test_tokenizeRegexStep,
 	test_tokenizeRegexFn,