Add set[char] parser

src/test.nim

@@ -109,6 +109,38 @@ proc initParser(str: string): ParserResult =
     tokens: newSeq[Token](),
   ).ok()
 
+func ch(expectedChars: set[char]): (Parser -> ParserResult) {.inline.} =
+  return func(parser: Parser): ParserResult =
+    let state = parser.state
+    let newIndex = state.position + 1
+
+    if newIndex > (state.stream.len - 1):
+      return err(ParserError(
+        kind: endOfStringErr,
+        expected: &"{expectedChars.prettyExpectedSet()}",
+        index: newIndex,
+        parser: parser,
+      ))
+    else:
+      let foundChar = state.stream[newIndex]
+      if foundChar in expectedChars:
+        return Parser(
+          state: ParserState(
+            stream: state.stream,
+            position: newIndex,
+            lastPosition: parser.state.position,
+          ),
+          tokens: parser.tokens & Token(value: foundChar)
+        ).ok()
+      else:
+        return err(ParserError(
+          kind: charMismatchErr,
+          unexpected: &"{foundChar}",
+          expected: &"{expectedChars.prettyExpectedSet()}",
+          index: newIndex,
+          parser: parser,
+        ))
+
 func ch(expectedChar: char): (Parser -> ParserResult) {.inline.} =
   return func(parser: Parser): ParserResult =
     let state = parser.state