conlang: Rename literals; split, compose, and document Rules

- Renamed literal Types to reflect their literal nature
  - This allows for consistent naming across future non-literal Types
- Complicated lexer Rules have been split into composable sub-rules,
  and moved into the Rule struct.
  - This improves modularity, and allows sharing of sub-rules across rules.
- Documented each lexer rule with (at least) a one-line blurb
  describing its function

.gitignore

@@ -1,2 +1,3 @@
 **/Cargo.lock
 target
+*.pest

dummy.cl

@@ -2,3 +2,8 @@
 // This is an example Conlang file.
 
 /* Conlang supports block comments! */
+ident  // Identifier
+.1     // literal float
+0.1    // literal float
+0x1234 // literal integer
+"str"  // literal string

libconlang/examples/identify_tokens.rs

@@ -1,18 +1,16 @@
 //! This example grabs input from stdin, lexes it, and prints which lexer rules matched
 #![allow(unused_imports)]
 use conlang::lexer::Lexer;
-use std::{io::stdin, error::Error};
+use std::{error::Error, io::stdin};
 
 fn main() -> Result<(), Box<dyn Error>> {
     // get input from stdin
     for line in stdin().lines() {
         let line = line?;
-        // lex the line
-        for func in [Lexer::line_comment, Lexer::block_comment, Lexer::shebang_comment, Lexer::identifier, Lexer::integer, Lexer::float, Lexer::string] {
-            if let Some(token) = func(&mut Lexer::new(&line)) {
+        let mut lexer = Lexer::new(&line);
+        while let Some(token) = lexer.any() {
             println!("{:?}: {}", token, &line[token.range()])
         }
     }
-    }
     Ok(())
 }

libconlang/src/lib.rs

@@ -9,10 +9,12 @@ pub mod token {
     pub enum Type {
         Comment,
         Identifier,
-        Integer,
-        Float,
-        String,
+        // Literals
+        LitInteger,
+        LitFloat,
+        LitString,
     }
+
     #[derive(Clone, Copy, Debug, PartialEq, Eq)]
     pub struct Token {
         ty: Type,
@@ -59,104 +61,60 @@ pub mod lexer {
         pub fn new(text: &'t str) -> Self {
             Self { text, cursor: 0 }
         }
+        /// Skips whitespace in the text
         fn skip_whitespace(&mut self) {
             if let Some(len) = Rule::new(self.text()).and_any(Rule::whitespace).end() {
                 self.cursor += len
             }
         }
+        /// Advances the cursor and produces a token
         fn produce_token(&mut self, ty: Type, len: usize) -> Option<Token> {
             let start = self.cursor;
             self.cursor += len;
             Some(Token::new(ty, start, self.cursor))
         }
+        /// Gets a slice of text beginning at the cursor
         fn text(&self) -> &str {
             &self.text[self.cursor..]
         }
+        // classifies a single arbitrary token
+        pub fn any(&mut self) -> Option<Token> {
+            None.or_else(|| self.comment())
+                .or_else(|| self.identifier())
+                .or_else(|| self.literal())
+        }
+        pub fn literal(&mut self) -> Option<Token> {
+            None.or_else(|| self.lit_string())
+                .or_else(|| self.lit_float())
+                .or_else(|| self.lit_integer())
+        }
         // functions for lexing individual tokens
-        pub fn line_comment(&mut self) -> Option<Token> {
-            // line_comment := "//" ~ (^newline)*
+        // comments
+        pub fn comment(&mut self) -> Option<Token> {
             self.skip_whitespace();
-            self.produce_token(
-                Type::Comment,
-                Rule::new(self.text())
-                    .str("//")
-                    .and_any(|rule| rule.not_char('\n'))
-                    .end()?,
-            )
-        }
-        pub fn block_comment(&mut self) -> Option<Token> {
-            // block_comment := "/*" ~ (block_comment | all_but("*/"))* ~ "*/"
-            self.skip_whitespace();
-            self.produce_token(
-                Type::Comment,
-                Rule::new(self.text())
-                    .str("/*")
-                    .and_any(|rule| rule.not_str("*/"))
-                    .str("*/")
-                    .end()?,
-            )
-        }
-        pub fn shebang_comment(&mut self) -> Option<Token> {
-            // shebang_comment := "#!/" ~ (^newline)*
-            self.skip_whitespace();
-            self.produce_token(
-                Type::Comment,
-                Rule::new(self.text())
-                    .str("#!/")
-                    .and_any(|rule| rule.not_char('\n'))
-                    .end()?,
-            )
+            self.produce_token(Type::Comment, Rule::new(self.text()).comment().end()?)
         }
+        // identifiers
         pub fn identifier(&mut self) -> Option<Token> {
             self.skip_whitespace();
-            self.produce_token(
-                Type::Identifier,
-                Rule::new(self.text())
-                    .char('_')
-                    .or(Rule::xid_start)
-                    .and_any(Rule::xid_continue)
-                    .end()?,
-            )
+            self.produce_token(Type::Identifier, Rule::new(self.text()).identifier().end()?)
         }
-        pub fn integer(&mut self) -> Option<Token> {
+        // literals
+        pub fn lit_integer(&mut self) -> Option<Token> {
             self.skip_whitespace();
-            self.produce_token(
-                Type::Integer,
-                Rule::new(self.text())
-                    .and_one_of(&[
-                        &|rule| rule.str("0x").and_any(Rule::hex_digit),
-                        &|rule| rule.str("0d").and_any(Rule::dec_digit),
-                        &|rule| rule.str("0o").and_any(Rule::oct_digit),
-                        &|rule| rule.str("0b").and_any(Rule::bin_digit),
-                        &|rule| rule.and_many(Rule::dec_digit),
-                    ])
-                    .end()?,
-            )
+            self.produce_token(Type::LitInteger, Rule::new(self.text()).integer().end()?)
         }
-        pub fn float(&mut self) -> Option<Token> {
+        pub fn lit_float(&mut self) -> Option<Token> {
             self.skip_whitespace();
-            self.produce_token(
-                Type::Float,
-                Rule::new(self.text())
-                    .and_any(Rule::dec_digit)
-                    .char('.')
-                    .and_many(Rule::dec_digit)
-                    .end()?,
-            )
+            self.produce_token(Type::LitFloat, Rule::new(self.text()).float().end()?)
         }
-        pub fn string(&mut self) -> Option<Token> {
+        pub fn lit_string(&mut self) -> Option<Token> {
             self.skip_whitespace();
-            self.produce_token(
-                Type::String,
-                Rule::new(self.text())
-                    .char('"')
-                    .and_any(|rule| rule.and(Rule::string_escape).or(|rule| rule.not_char('"')))
-                    .char('"')
-                    .end()?,
-            )
+            self.produce_token(Type::LitString, Rule::new(self.text()).string().end()?)
         }
     }
 
+    /// A lexer [Rule] matches patterns in text in a declarative manner
     #[derive(Clone, Debug, PartialEq, Eq)]
     pub struct Rule<'t> {
         text: &'t str,
@@ -176,53 +134,135 @@ pub mod lexer {
     }
 
     impl<'t> Rule<'t> {
+        /// Matches a block, line, or shebang comment
+        pub fn comment(self) -> Self {
+            self.and_either(Self::line_comment, Self::block_comment)
+        }
+        /// Matches a line or shebang comment
+        fn line_comment(self) -> Self {
+            // line_comment := ("//" | "#!/") (!newline)*
+            self.str("//")
+                .or(|r| r.str("#!/"))
+                .and_any(|r| r.not_char('\n'))
+        }
+        /// Matches a block comment
+        fn block_comment(self) -> Self {
+            // block_comment := "/*" (block_comment | all_but("*/"))* "*/"
+            self.str("/*")
+                .and_any(|r| r.and_either(|f| f.block_comment(), |g| g.not_str("*/")))
+                .str("*/")
+        }
+        /// Matches a Rust-style identifier
+        pub fn identifier(self) -> Self {
+            // identifier := ('_' | XID_START) ~ XID_CONTINUE*
+            self.char('_')
+                .or(Rule::xid_start)
+                .and_any(Rule::xid_continue)
+        }
+        /// Matches a Rust-style base-prefixed int literal
+        fn int_literal_kind(self, prefix: &str, digit: impl Fn(Self) -> Self) -> Self {
+            // int_kind<Prefix, Digit> := Prefix '_'* Digit (Digit | '_')*
+            self.str(prefix)
+                .and_any(|r| r.char('_'))
+                .and(&digit)
+                .and_any(|r| r.and(&digit).or(|r| r.char('_')))
+        }
+        /// Matches a Rust-style integer literal
+        pub fn integer(self) -> Self {
+            // integer = (int_kind<0d, dec_digit> | int_kind<0x, hex_digit>
+            //           | int_kind<0o, oct_digit> | int_kind<0b, bin_digit> | dec_digit (dec_digit | '_')*)
+            self.and_one_of(&[
+                &|rule| rule.int_literal_kind("0d", Rule::dec_digit),
+                &|rule| rule.int_literal_kind("0x", Rule::hex_digit),
+                &|rule| rule.int_literal_kind("0o", Rule::oct_digit),
+                &|rule| rule.int_literal_kind("0b", Rule::bin_digit),
+                &|rule| {
+                    rule.dec_digit()
+                        .and_any(|r| r.dec_digit().or(|r| r.char('_')))
+                },
+            ])
+        }
+        /// Matches a float literal
+        // TODO: exponent form
+        pub fn float(self) -> Self {
+            self.and_any(Rule::dec_digit)
+                .char('.')
+                .and_many(Rule::dec_digit)
+        }
+        /// Matches one quote-delimited string literal
+        pub fn string(self) -> Self {
+            self.char('"').and_any(Rule::string_continue).char('"')
+        }
+        /// Matches one string escape sequence or non-`"` characcter
+        pub fn string_continue(self) -> Self {
+            self.and(Rule::string_escape).or(|rule| rule.not_char('"'))
+        }
+    }
+
+    impl<'t> Rule<'t> {
+        /// Matches a char lexicographically between start and end
         pub fn char_between(self, start: char, end: char) -> Self {
             self.char_fn(|c| start <= c && c <= end)
         }
+        /// Matches a single char
         pub fn char(self, c: char) -> Self {
             self.has(|rule| rule.text.starts_with(c), 1)
         }
+        /// Matches the entirety of a string slice
         pub fn str(self, s: &str) -> Self {
             self.has(|rule| rule.text.starts_with(s), s.len())
         }
+        /// Matches a char based on the output of a function
         pub fn char_fn(self, f: impl Fn(char) -> bool) -> Self {
             self.and(|rule| match rule.text.strip_prefix(&f) {
                 Some(text) => Self { text, taken: rule.taken + next_utf8(rule.text, 1), ..rule },
                 None => Self { is_alright: false, ..rule },
             })
         }
+        /// Matches a single char except c
         pub fn not_char(self, c: char) -> Self {
             self.has(|rule| !rule.text.starts_with(c), 1)
         }
+        /// Matches a single char unless the text starts with s
         pub fn not_str(self, s: &str) -> Self {
             self.has(|rule| !rule.text.starts_with(s), 1)
         }
+        // commonly used character classes
+        /// Matches one of any character
         pub fn any(self) -> Self {
             self.has(|_| true, 1)
         }
+        /// Matches one whitespace
         pub fn whitespace(self) -> Self {
             self.char_fn(|c| c.is_whitespace())
         }
+        /// Matches one XID_START
         pub fn xid_start(self) -> Self {
             use unicode_xid::UnicodeXID;
             self.char_fn(UnicodeXID::is_xid_start)
         }
+        /// Matches one XID_CONTINUE
         pub fn xid_continue(self) -> Self {
             use unicode_xid::UnicodeXID;
             self.char_fn(UnicodeXID::is_xid_continue)
         }
+        /// Matches one hexadecimal digit
         pub fn hex_digit(self) -> Self {
             self.char_fn(|c| c.is_ascii_hexdigit())
         }
+        /// Matches one decimal digit
         pub fn dec_digit(self) -> Self {
             self.char_fn(|c| c.is_ascii_digit())
         }
+        /// Matches one octal digit
         pub fn oct_digit(self) -> Self {
             self.char_between('0', '7')
         }
+        /// Matches one binary digit
         pub fn bin_digit(self) -> Self {
             self.char_between('0', '1')
         }
+        /// Matches any string escape "\."
         pub fn string_escape(self) -> Self {
             self.char('\\').and(Rule::any)
         }
@@ -281,6 +321,8 @@ mod tests {
         // TODO
     }
     mod lexer {
+        use std::ops::Range;
+
         use crate::{
             lexer::*,
             token::{Token, Type},
@@ -288,11 +330,13 @@ mod tests {
 
         fn assert_whole_input_is_token<'t, F>(input: &'t str, f: F, ty: Type)
         where F: FnOnce(&mut Lexer<'t>) -> Option<Token> {
-            assert_has_type_and_len(input, f, ty, input.len())
+            assert_has_type_and_range(input, f, ty, 0..input.len())
         }
-        fn assert_has_type_and_len<'t, F>(input: &'t str, f: F, ty: Type, len: usize)
+        fn assert_has_type_and_range<'t, F>(input: &'t str, f: F, ty: Type, range: Range<usize>)
         where F: FnOnce(&mut Lexer<'t>) -> Option<Token> {
-            assert_eq!(Some(Token::new(ty, 0, len)), f(&mut Lexer::new(input)),)
+            let tok = f(&mut Lexer::new(input)).unwrap();
+            assert_eq!(ty, tok.ty());
+            assert_eq!(range, tok.range());
         }
 
         mod comment {
@@ -300,42 +344,47 @@ mod tests {
 
             #[test]
             fn line_comment() {
+                assert_whole_input_is_token("// comment!", Lexer::comment, Type::Comment);
+            }
+            #[test]
+            #[should_panic]
+            fn not_line_comment() {
+                assert_whole_input_is_token("fn main() {}", Lexer::comment, Type::Comment);
+            }
+            #[test]
+            fn block_comment() {
+                assert_whole_input_is_token("/* comment! */", Lexer::comment, Type::Comment);
+            }
+            #[test]
+            fn nested_block_comment() {
                 assert_whole_input_is_token(
-                    "// this is a comment",
-                    Lexer::line_comment,
+                    "/* a /* nested */ comment */",
+                    Lexer::comment,
                     Type::Comment,
                 );
             }
             #[test]
             #[should_panic]
-            fn not_line_comment() {
-                assert_whole_input_is_token("fn main() {}", Lexer::line_comment, Type::Comment);
-            }
-            #[test]
-            fn block_comment() {
+            fn unclosed_nested_comment() {
                 assert_whole_input_is_token(
-                    "/* this is a comment */",
-                    Lexer::block_comment,
+                    "/* improperly /* nested */ comment",
+                    Lexer::comment,
                     Type::Comment,
                 );
             }
             #[test]
             #[should_panic]
             fn not_block_comment() {
-                assert_whole_input_is_token("fn main() {}", Lexer::block_comment, Type::Comment);
+                assert_whole_input_is_token("fn main() {}", Lexer::comment, Type::Comment);
             }
             #[test]
             fn shebang_comment() {
-                assert_whole_input_is_token(
-                    "#!/ this is a comment",
-                    Lexer::shebang_comment,
-                    Type::Comment,
-                );
+                assert_whole_input_is_token("#!/ comment!", Lexer::comment, Type::Comment);
             }
             #[test]
             #[should_panic]
             fn not_shebang_comment() {
-                assert_whole_input_is_token("fn main() {}", Lexer::shebang_comment, Type::Comment);
+                assert_whole_input_is_token("fn main() {}", Lexer::comment, Type::Comment);
             }
         }
         mod identifier {
@@ -366,65 +415,70 @@ mod tests {
             use super::*;
             #[test]
             fn bare() {
-                assert_whole_input_is_token("10010110", Lexer::integer, Type::Integer);
-                assert_whole_input_is_token("12345670", Lexer::integer, Type::Integer);
-                assert_whole_input_is_token("1234567890", Lexer::integer, Type::Integer);
+                assert_whole_input_is_token("10010110", Lexer::lit_integer, Type::LitInteger);
+                assert_whole_input_is_token("12345670", Lexer::lit_integer, Type::LitInteger);
+                assert_whole_input_is_token("1234567890", Lexer::lit_integer, Type::LitInteger);
             }
             #[test]
             fn base16() {
-                assert_has_type_and_len("0x1234", Lexer::integer, Type::Integer, 6);
-                assert_has_type_and_len("0x1234 \"hello\"", Lexer::integer, Type::Integer, 6);
+                assert_has_type_and_range("0x1234", Lexer::lit_integer, Type::LitInteger, 0..6);
+                assert_has_type_and_range(
+                    "0x1234 \"hello\"",
+                    Lexer::lit_integer,
+                    Type::LitInteger,
+                    0..6,
+                );
             }
             #[test]
             fn base10() {
-                assert_whole_input_is_token("0d1234", Lexer::integer, Type::Integer);
+                assert_whole_input_is_token("0d1234", Lexer::lit_integer, Type::LitInteger);
             }
             #[test]
             fn base8() {
-                assert_whole_input_is_token("0o1234", Lexer::integer, Type::Integer);
+                assert_whole_input_is_token("0o1234", Lexer::lit_integer, Type::LitInteger);
             }
             #[test]
             fn base2() {
-                assert_whole_input_is_token("0b1010", Lexer::integer, Type::Integer);
+                assert_whole_input_is_token("0b1010", Lexer::lit_integer, Type::LitInteger);
             }
         }
         mod float {
             use super::*;
             #[test]
             fn number_dot_number_is_float() {
-                assert_whole_input_is_token("1.0", Lexer::float, Type::Float);
+                assert_whole_input_is_token("1.0", Lexer::lit_float, Type::LitFloat);
             }
             #[test]
             fn nothing_dot_number_is_float() {
-                assert_whole_input_is_token(".0", Lexer::float, Type::Float);
+                assert_whole_input_is_token(".0", Lexer::lit_float, Type::LitFloat);
             }
             #[test]
             #[should_panic]
             fn number_dot_nothing_is_not_float() {
-                assert_whole_input_is_token("1.", Lexer::float, Type::Float);
+                assert_whole_input_is_token("1.", Lexer::lit_float, Type::LitFloat);
             }
             #[test]
             #[should_panic]
             fn nothing_dot_nothing_is_not_float() {
-                assert_whole_input_is_token(".", Lexer::float, Type::Float);
+                assert_whole_input_is_token(".", Lexer::lit_float, Type::LitFloat);
             }
         }
         mod string {
             use super::*;
             #[test]
             fn empty_string() {
-                assert_whole_input_is_token("\"\"", Lexer::string, Type::String);
+                assert_whole_input_is_token("\"\"", Lexer::lit_string, Type::LitString);
             }
             #[test]
             fn unicode_string() {
-                assert_whole_input_is_token("\"I 💙 🦈!\"", Lexer::string, Type::String);
+                assert_whole_input_is_token("\"I 💙 🦈!\"", Lexer::lit_string, Type::LitString);
             }
             #[test]
             fn escape_string() {
                 assert_whole_input_is_token(
                     r#"" \"This is a quote\" ""#,
-                    Lexer::string,
-                    Type::String,
+                    Lexer::lit_string,
+                    Type::LitString,
                 );
             }
         }