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|
## This is LuxC's parser.
## It takes the source code of a Lux file in raw text form and
## extracts the syntactic structure of the code from it.
## It only produces Lux Code nodes, and thus removes any white-space
## and comments while processing its inputs.
## Another important aspect of the parser is that it keeps track of
## its position within the input data.
## That is, the parser takes into account the line and column
## information in the input text (it doesn't really touch the
## file-name aspect of the cursor, leaving it intact in whatever
## base-line cursor it is given).
## This particular piece of functionality is not located in one
## function, but it is instead scattered throughout several parsers,
## since the logic for how to update the cursor varies, depending on
## what is being parsed, and the rules involved.
## You will notice that several parsers have a "where" parameter, that
## tells them the cursor position prior to the parser being run.
## They are supposed to produce some parsed output, alongside an
## updated cursor pointing to the end position, after the parser was run.
## Lux Code nodes/tokens are annotated with cursor meta-data
## (file-name, line, column) to keep track of their provenance and
## location, which is helpful for documentation and debugging.
(.module:
[lux (#- nat int rev)
[control
monad
["p" parser ("parser/" Monad<Parser>)]
["ex" exception (#+ exception:)]]
[data
["e" error]
[number]
[product]
[maybe]
["." text
["l" lexer]
format]
[collection
[row (#+ Row)]
["dict" dictionary (#+ Dictionary)]]]])
(type: #export Aliases (Dictionary Text Text))
(def: white-space Text "\t\v \r\f")
(def: new-line Text "\n")
## This is the parser for white-space.
## Whenever a new-line is encountered, the column gets reset to 0, and
## the line gets incremented.
## It operates recursively in order to produce the longest continuous
## chunk of white-space.
(def: (space^ where)
(-> Cursor (l.Lexer [Cursor Text]))
(p.either (do p.Monad<Parser>
[content (l.many (l.one-of white-space))]
(wrap [(update@ #.column (n/+ (text.size content)) where)
content]))
## New-lines must be handled as a separate case to ensure line
## information is handled properly.
(do p.Monad<Parser>
[content (l.many (l.one-of new-line))]
(wrap [(|> where
(update@ #.line (n/+ (text.size content)))
(set@ #.column +0))
content]))
))
## Single-line comments can start anywhere, but only go up to the
## next new-line.
(def: (single-line-comment^ where)
(-> Cursor (l.Lexer [Cursor Text]))
(do p.Monad<Parser>
[_ (l.this "##")
comment (l.some (l.none-of new-line))
_ (l.this new-line)]
(wrap [(|> where
(update@ #.line inc)
(set@ #.column +0))
comment])))
## This is just a helper parser to find text which doesn't run into
## any special character sequences for multi-line comments.
(def: comment-bound^
(l.Lexer Any)
($_ p.either
(l.this new-line)
(l.this ")#")
(l.this "#(")))
## Multi-line comments are bounded by #( these delimiters, #(and, they may
## also be nested)# )#.
## Multi-line comment syntax must be balanced.
## That is, any nested comment must have matched delimiters.
## Unbalanced comments ought to be rejected as invalid code.
(def: (multi-line-comment^ where)
(-> Cursor (l.Lexer [Cursor Text]))
(do p.Monad<Parser>
[_ (l.this "#(")]
(loop [comment ""
where (update@ #.column (n/+ +2) where)]
($_ p.either
## These are normal chunks of commented text.
(do @
[chunk (l.many (l.not comment-bound^))]
(recur (format comment chunk)
(|> where
(update@ #.column (n/+ (text.size chunk))))))
## This is a special rule to handle new-lines within
## comments properly.
(do @
[_ (l.this new-line)]
(recur (format comment new-line)
(|> where
(update@ #.line inc)
(set@ #.column +0))))
## This is the rule for handling nested sub-comments.
## Ultimately, the whole comment is just treated as text
## (the comment must respect the syntax structure, but the
## output produced is just a block of text).
## That is why the sub-comment is covered in delimiters
## and then appended to the rest of the comment text.
(do @
[[sub-where sub-comment] (multi-line-comment^ where)]
(recur (format comment "#(" sub-comment ")#")
sub-where))
## Finally, this is the rule for closing the comment.
(do @
[_ (l.this ")#")]
(wrap [(update@ #.column (n/+ +2) where)
comment]))
))))
## This is the only parser that should be used directly by other
## parsers, since all comments must be treated as either being
## single-line or multi-line.
## That is, there is no syntactic rule prohibiting one type of comment
## from being used in any situation (alternatively, forcing one type
## of comment to be the only usable one).
(def: (comment^ where)
(-> Cursor (l.Lexer [Cursor Text]))
(p.either (single-line-comment^ where)
(multi-line-comment^ where)))
## To simplify parsing, I remove any left-padding that an Code token
## may have prior to parsing the token itself.
## Left-padding is assumed to be either white-space or a comment.
## The cursor gets updated, but the padding gets ignored.
(def: (left-padding^ where)
(-> Cursor (l.Lexer Cursor))
($_ p.either
(do p.Monad<Parser>
[[where comment] (comment^ where)]
(left-padding^ where))
(do p.Monad<Parser>
[[where white-space] (space^ where)]
(left-padding^ where))
(:: p.Monad<Parser> wrap where)))
## Escaped character sequences follow the usual syntax of
## back-slash followed by a letter (e.g. \n).
## Unicode escapes are possible, with hexadecimal sequences between 1
## and 4 characters long (e.g. \u12aB).
## Escaped characters may show up in Char and Text literals.
(def: escaped-char^
(l.Lexer [Nat Text])
(p.after (l.this "\\")
(do p.Monad<Parser>
[code l.any]
(case code
## Handle special cases.
"t" (wrap [+2 "\t"])
"v" (wrap [+2 "\v"])
"b" (wrap [+2 "\b"])
"n" (wrap [+2 "\n"])
"r" (wrap [+2 "\r"])
"f" (wrap [+2 "\f"])
"\"" (wrap [+2 "\""])
"\\" (wrap [+2 "\\"])
## Handle unicode escapes.
"u"
(do p.Monad<Parser>
[code (l.between +1 +4 l.hexadecimal)]
(wrap (case (|> code (format "+") (:: number.Hex@Codec<Text,Nat> decode))
(#.Right value)
[(n/+ +2 (text.size code)) (text.from-code value)]
_
(undefined))))
_
(p.fail (format "Invalid escaping syntax: " (%t code)))))))
## These are very simple parsers that just cut chunks of text in
## specific shapes and then use decoders already present in the
## standard library to actually produce the values from the literals.
(def: rich-digit
(l.Lexer Text)
(p.either l.decimal
(p.after (l.this "_") (parser/wrap ""))))
(def: rich-digits^
(l.Lexer Text)
(l.seq l.decimal
(l.some rich-digit)))
(do-template [<name> <tag> <lexer> <codec>]
[(def: #export (<name> where)
(-> Cursor (l.Lexer [Cursor Code]))
(do p.Monad<Parser>
[chunk <lexer>]
(case (:: <codec> decode chunk)
(#.Left error)
(p.fail error)
(#.Right value)
(wrap [(update@ #.column (n/+ (text.size chunk)) where)
[where (<tag> value)]]))))]
[int #.Int
(l.seq (p.default "" (l.one-of "-"))
rich-digits^)
number.Codec<Text,Int>]
[rev #.Rev
(l.seq (l.one-of ".")
rich-digits^)
number.Codec<Text,Rev>]
)
(def: (nat-char where)
(-> Cursor (l.Lexer [Cursor Code]))
(do p.Monad<Parser>
[_ (l.this "#\"")
[where' char] (: (l.Lexer [Cursor Text])
($_ p.either
## Normal text characters.
(do @
[normal (l.none-of "\\\"\n")]
(wrap [(|> where
(update@ #.column inc))
normal]))
## Must handle escaped
## chars separately.
(do @
[[chars-consumed char] escaped-char^]
(wrap [(|> where
(update@ #.column (n/+ chars-consumed)))
char]))))
_ (l.this "\"")
#let [char (maybe.assume (text.nth +0 char))]]
(wrap [(|> where'
(update@ #.column inc))
[where (#.Nat char)]])))
(def: (normal-nat where)
(-> Cursor (l.Lexer [Cursor Code]))
(do p.Monad<Parser>
[chunk (l.seq (l.one-of "+")
rich-digits^)]
(case (:: number.Codec<Text,Nat> decode chunk)
(#.Left error)
(p.fail error)
(#.Right value)
(wrap [(update@ #.column (n/+ (text.size chunk)) where)
[where (#.Nat value)]]))))
(def: #export (nat where)
(-> Cursor (l.Lexer [Cursor Code]))
(p.either (normal-nat where)
(nat-char where)))
(def: (normal-frac where)
(-> Cursor (l.Lexer [Cursor Code]))
(do p.Monad<Parser>
[chunk ($_ l.seq
(p.default "" (l.one-of "-"))
rich-digits^
(l.one-of ".")
rich-digits^
(p.default ""
($_ l.seq
(l.one-of "eE")
(p.default "" (l.one-of "+-"))
rich-digits^)))]
(case (:: number.Codec<Text,Frac> decode chunk)
(#.Left error)
(p.fail error)
(#.Right value)
(wrap [(update@ #.column (n/+ (text.size chunk)) where)
[where (#.Frac value)]]))))
(def: frac-ratio-fragment
(l.Lexer Frac)
(<| (p.codec number.Codec<Text,Frac>)
(:: p.Monad<Parser> map (function (_ digits)
(format digits ".0")))
rich-digits^))
(def: (ratio-frac where)
(-> Cursor (l.Lexer [Cursor Code]))
(do p.Monad<Parser>
[chunk ($_ l.seq
(p.default "" (l.one-of "-"))
rich-digits^
(l.one-of "/")
rich-digits^)
value (l.local chunk
(do @
[signed? (l.this? "-")
numerator frac-ratio-fragment
_ (l.this? "/")
denominator frac-ratio-fragment
_ (p.assert "Denominator cannot be 0."
(not (f/= 0.0 denominator)))]
(wrap (|> numerator
(f/* (if signed? -1.0 1.0))
(f// denominator)))))]
(wrap [(update@ #.column (n/+ (text.size chunk)) where)
[where (#.Frac value)]])))
(def: #export (frac where)
(-> Cursor (l.Lexer [Cursor Code]))
(p.either (normal-frac where)
(ratio-frac where)))
## This parser looks so complex because text in Lux can be multi-line
## and there are rules regarding how this is handled.
(def: #export (text where)
(-> Cursor (l.Lexer [Cursor Code]))
(do p.Monad<Parser>
[## Lux text "is delimited by double-quotes", as usual in most
## programming languages.
_ (l.this "\"")
## I must know what column the text body starts at (which is
## always 1 column after the left-delimiting quote).
## This is important because, when procesing subsequent lines,
## they must all start at the same column, being left-padded with
## as many spaces as necessary to be column-aligned.
## This helps ensure that the formatting on the text in the
## source-code matches the formatting of the Text value.
#let [offset-column (inc (get@ #.column where))]
[where' text-read] (: (l.Lexer [Cursor Text])
## I must keep track of how much of the
## text body has been read, how far the
## cursor has progressed, and whether I'm
## processing a subsequent line, or just
## processing normal text body.
(loop [text-read ""
where (|> where
(update@ #.column inc))
must-have-offset? #0]
(p.either (if must-have-offset?
## If I'm at the start of a
## new line, I must ensure the
## space-offset is at least
## as great as the column of
## the text's body's column,
## to ensure they are aligned.
(do @
[offset (l.many (l.one-of " "))
#let [offset-size (text.size offset)]]
(if (n/>= offset-column offset-size)
## Any extra offset
## becomes part of the
## text's body.
(recur (|> offset
(text.split offset-column)
(maybe.default (undefined))
product.right
(format text-read))
(|> where
(update@ #.column (n/+ offset-size)))
#0)
(p.fail (format "Each line of a multi-line text must have an appropriate offset!\n"
"Expected: " (%i (.int offset-column)) " columns.\n"
" Actual: " (%i (.int offset-size)) " columns.\n"))))
($_ p.either
## Normal text characters.
(do @
[normal (l.many (l.none-of "\\\"\n"))]
(recur (format text-read normal)
(|> where
(update@ #.column (n/+ (text.size normal))))
#0))
## Must handle escaped
## chars separately.
(do @
[[chars-consumed char] escaped-char^]
(recur (format text-read char)
(|> where
(update@ #.column (n/+ chars-consumed)))
#0))
## The text ends when it
## reaches the right-delimiter.
(do @
[_ (l.this "\"")]
(wrap [(update@ #.column inc where)
text-read]))))
## If a new-line is
## encountered, it gets
## appended to the value and
## the loop is alerted that the
## next line must have an offset.
(do @
[_ (l.this new-line)]
(recur (format text-read new-line)
(|> where
(update@ #.line inc)
(set@ #.column +0))
#1)))))]
(wrap [where'
[where (#.Text text-read)]])))
## Form and tuple syntax is mostly the same, differing only in the
## delimiters involved.
## They may have an arbitrary number of arbitrary Code nodes as elements.
(do-template [<name> <tag> <open> <close>]
[(def: (<name> where ast)
(-> Cursor
(-> Cursor (l.Lexer [Cursor Code]))
(l.Lexer [Cursor Code]))
(do p.Monad<Parser>
[_ (l.this <open>)
[where' elems] (loop [elems (: (Row Code)
row.empty)
where where]
(p.either (do @
[## Must update the cursor as I
## go along, to keep things accurate.
[where' elem] (ast where)]
(recur (row.add elem elems)
where'))
(do @
[## Must take into account any
## padding present before the
## end-delimiter.
where' (left-padding^ where)
_ (l.this <close>)]
(wrap [(update@ #.column inc where')
(row.to-list elems)]))))]
(wrap [where'
[where (<tag> elems)]])))]
[form #.Form "(" ")"]
[tuple #.Tuple "[" "]"]
)
## Records are almost (syntactically) the same as forms and tuples,
## with the exception that their elements must come in pairs (as in
## key-value pairs).
## Semantically, though, records and tuples are just 2 different
## representations for the same thing (a tuple).
## In normal Lux syntax, the key position in the pair will be a tag
## Code node, however, record Code nodes allow any Code node to occupy
## this position, since it may be useful when processing Code syntax in
## macros.
(def: (record where ast)
(-> Cursor
(-> Cursor (l.Lexer [Cursor Code]))
(l.Lexer [Cursor Code]))
(do p.Monad<Parser>
[_ (l.this "{")
[where' elems] (loop [elems (: (Row [Code Code])
row.empty)
where where]
(p.either (do @
[[where' key] (ast where)
[where' val] (ast where')]
(recur (row.add [key val] elems)
where'))
(do @
[where' (left-padding^ where)
_ (l.this "}")]
(wrap [(update@ #.column inc where')
(row.to-list elems)]))))]
(wrap [where'
[where (#.Record elems)]])))
## The parts of an identifier are separated by a single mark.
## E.g. module.name.
## Only one such mark may be used in an identifier, since there
## can only be 2 parts to an identifier (the module [before the
## mark], and the name [after the mark]).
## There are also some extra rules regarding identifier syntax,
## encoded on the parser.
(def: identifier-separator Text ".")
## A Lux identifier is a pair of chunks of text, where the first-part
## refers to the module that gives context to the identifier, and the
## second part corresponds to the name of the identifier itself.
## The module part may be absent (by being the empty text ""), but the
## name part must always be present.
## The rules for which characters you may use are specified in terms
## of which characters you must avoid (to keep things as open-ended as
## possible).
## In particular, no white-space can be used, and neither can other
## characters which are already used by Lux as delimiters for other
## Code nodes (thereby reducing ambiguity while parsing).
## Additionally, the first character in an identifier's part cannot be
## a digit, to avoid confusion with regards to numbers.
(def: ident-part^
(l.Lexer Text)
(do p.Monad<Parser>
[#let [digits "0123456789"
delimiters (format "()[]{}#\"" identifier-separator)
space (format white-space new-line)
head-lexer (l.none-of (format digits delimiters space))
tail-lexer (l.some (l.none-of (format delimiters space)))]
head head-lexer
tail tail-lexer]
(wrap (format head tail))))
(def: current-module-mark Text (format identifier-separator identifier-separator))
(def: (ident^ current-module aliases)
(-> Text Aliases (l.Lexer [Ident Nat]))
($_ p.either
## When an identifier starts with 2 marks, its module is
## taken to be the current-module being compiled at the moment.
## This can be useful when mentioning identifiers and tags
## inside quoted/templated code in macros.
(do p.Monad<Parser>
[_ (l.this current-module-mark)
def-name ident-part^]
(wrap [[current-module def-name]
(n/+ +2 (text.size def-name))]))
## If the identifier is prefixed by the mark, but no module
## part, the module is assumed to be "lux" (otherwise known as
## the 'prelude').
## This makes it easy to refer to definitions in that module,
## since it is the most fundamental module in the entire
## standard library.
(do p.Monad<Parser>
[_ (l.this identifier-separator)
def-name ident-part^]
(wrap [["lux" def-name]
(inc (text.size def-name))]))
## Not all identifiers must be specified with a module part.
## If that part is not provided, the identifier will be created
## with the empty "" text as the module.
## During program analysis, such identifiers tend to be treated
## as if their context is the current-module, but this only
## applies to identifiers for tags and module definitions.
## Function arguments and local-variables may not be referred-to
## using identifiers with module parts, so being able to specify
## identifiers with empty modules helps with those use-cases.
(do p.Monad<Parser>
[first-part ident-part^]
(p.either (do @
[_ (l.this identifier-separator)
second-part ident-part^]
(wrap [[(|> aliases (dict.get first-part) (maybe.default first-part))
second-part]
($_ n/+
(text.size first-part)
+1
(text.size second-part))]))
(wrap [["" first-part]
(text.size first-part)])))))
(def: #export (tag current-module aliases where)
(-> Text Aliases Cursor (l.Lexer [Cursor Code]))
(do p.Monad<Parser>
[[value length] (p.after (l.this "#")
(ident^ current-module aliases))]
(wrap [(update@ #.column (|>> ($_ n/+ +1 length)) where)
[where (#.Tag value)]])))
(def: #export (symbol current-module aliases where)
(-> Text Aliases Cursor (l.Lexer [Cursor Code]))
(do p.Monad<Parser>
[[value length] (ident^ current-module aliases)]
(wrap [(update@ #.column (|>> (n/+ length)) where)
[where (case value
(^template [<name> <value>]
["" <name>]
(#.Bit <value>))
(["#0" #0]
["#1" #1])
_
(#.Symbol value))]])))
(exception: #export (end-of-file {module Text})
module)
(exception: #export (unrecognized-input {[file line column] Cursor})
(ex.report ["File" file]
["Line" (%n line)]
["Column" (%n column)]))
(def: (ast current-module aliases)
(-> Text Aliases Cursor (l.Lexer [Cursor Code]))
(: (-> Cursor (l.Lexer [Cursor Code]))
(function (ast' where)
(do p.Monad<Parser>
[where (left-padding^ where)]
($_ p.either
(form where ast')
(tuple where ast')
(record where ast')
(nat where)
(frac where)
(int where)
(rev where)
(symbol current-module aliases where)
(tag current-module aliases where)
(text where)
(do @
[end? l.end?]
(if end?
(p.fail (ex.construct end-of-file current-module))
(p.fail (ex.construct unrecognized-input where))))
)))))
(def: #export (read current-module aliases [where offset source])
(-> Text Aliases Source (e.Error [Source Code]))
(case (p.run [offset source] (ast current-module aliases where))
(#e.Error error)
(#e.Error error)
(#e.Success [[offset' remaining] [where' output]])
(#e.Success [[where' offset' remaining] output])))
|