LispInSmallPieces/chapter4/reader.coffee

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2015-08-15 16:43:48 +00:00
{car, cdr, cons, nil, nilp, pairp, vectorToList, list} = require 'cons-lists/lists'
{inspect} = require "util"
{Node, Comment, Symbol} = require "../chapter1/reader_types"
NEWLINES = ["\n", "\r", "\x0B", "\x0C"]
WHITESPACE = [" ", "\t"].concat(NEWLINES)
EOF = new (class Eof)()
EOO = new (class Eoo)()
class Source
constructor: (@inStream) ->
@index = 0
@max = @inStream.length - 1
@line = 0
@column = 0
peek: -> @inStream[@index]
position: -> [@line, @column]
next: ->
c = @peek()
return EOF if @done()
@index++
[@line, @column] = if @peek() in NEWLINES then [@line + 1, 0] else [@line, @column + 1]
c
done: -> @index > @max
# IO -> IO
skipWS = (inStream) ->
while inStream.peek() in WHITESPACE then inStream.next()
# msg -> (IO -> Node => Error)
handleError = (message) ->
(line, column) -> new Node('error', message, line, column)
# IO -> Node => Comment
readComment = (inStream) ->
[line, column] = inStream.position()
r = (while inStream.peek() != "\n" and not inStream.done()
inStream.next()).join("")
if not inStream.done()
inStream.next()
new Node 'comment', (new Comment r), line, column
# IO -> (Node => Literal => String) | Error
readString = (inStream) ->
[line, column] = inStream.position()
inStream.next()
string = until inStream.peek() == '"' or inStream.done()
if inStream.peek() == '\\'
inStream.next()
inStream.next()
if inStream.done()
return handleError("end of file seen before end of string.")(line, column)
inStream.next()
new Node 'string', (string.join ''), line, column
# (String) -> (Node => Literal => Number) | Nothing
readMaybeNumber = (symbol) ->
if symbol[0] == '+'
return readMaybeNumber symbol.substr(1)
if symbol[0] == '-'
ret = readMaybeNumber symbol.substr(1)
return if ret? then -1 * ret else undefined
if symbol.search(/^0x[0-9a-fA-F]+$/) > -1
return parseInt(symbol, 16)
if symbol.search(/^0[0-9a-fA-F]+$/) > -1
return parseInt(symbol, 8)
if symbol.search(/^[0-9]+$/) > -1
return parseInt(symbol, 10)
if symbol.search(/^nil$/) > -1
return nil
undefined
# (IO, macros) -> (IO, Node => Number | Symbol) | Error
readSymbol = (inStream, tableKeys) ->
[line, column] = inStream.position()
symbol = (until (inStream.done() or inStream.peek() in tableKeys or inStream.peek() in WHITESPACE)
inStream.next()).join ''
number = readMaybeNumber symbol
if number?
return new Node 'number', number, line, column
new Node 'symbol', (new Symbol symbol), line, column
# (Delim, TypeName) -> IO -> (IO, node) | Error
makeReadPair = (delim, type) ->
# IO -> (IO, Node) | Error
(inStream) ->
inStream.next()
skipWS inStream
[line, column] = inStream.position()
if inStream.peek() == delim
inStream.next()
return new Node type, nil, line, column
# IO -> (IO, Node) | Error
dotted = false
readEachPair = (inStream) ->
[line, column] = inStream.position()
obj = read inStream, true, null, true
if inStream.peek() == delim
if dotted then return obj
return cons obj, nil
if inStream.done() then return handleError("Unexpected end of input")(line, column)
if dotted then return handleError("More than one symbol after dot")
return obj if obj.type == 'error'
if obj.type == 'symbol' and obj.value == '.'
dotted = true
return readEachPair inStream
cons obj, readEachPair inStream
ret = new Node type, readEachPair(inStream), line, column
inStream.next()
ret
# Type -> (IO -> (IO, Node))
prefixReader = (type) ->
# IO -> (IO, Node)
(inStream) ->
[line, column] = inStream.position()
inStream.next()
[line1, column1] = inStream.position()
obj = read inStream, true, null, true
return obj if obj.type == 'error'
new Node "list", cons((new Node("symbol", type, line1, column1)), cons(obj)), line, column
# I really wanted to make anything more complex than a list (like an
# object or a vector) something handled by a read macro. Maybe in a
# future revision I can vertically de-integrate these.
readMacros =
'"': readString
'(': makeReadPair ')', 'list'
')': handleError "Closing paren encountered"
'[': makeReadPair ']', 'vector'
']': handleError "Closing bracket encountered"
'{': makeReadPair('}', 'record', (res) ->
res.length % 2 == 0 and true or mkerr "record key without value")
'}': handleError "Closing curly without corresponding opening."
"`": prefixReader 'back-quote'
"'": prefixReader 'quote'
",": prefixReader 'unquote'
";": readComment
# Given a stream, reads from the stream until a single complete lisp
# object has been found and returns the object
# IO -> Form
read = (inStream, eofErrorP = false, eofError = EOF, recursiveP = false, inReadMacros = null, keepComments = false) ->
inStream = if inStream instanceof Source then inStream else new Source inStream
inReadMacros = if InReadMacros? then inReadMacros else readMacros
inReadMacroKeys = (i for i of inReadMacros)
c = inStream.peek()
# (IO, Char) -> (IO, Node) | Error
matcher = (inStream, c) ->
if inStream.done()
return if recursiveP then handleError('EOF while processing nested object')(inStream) else nil
if c in WHITESPACE
inStream.next()
return nil
if c == ';'
return readComment(inStream)
ret = if c in inReadMacroKeys then inReadMacros[c](inStream) else readSymbol(inStream, inReadMacroKeys)
skipWS inStream
ret
while true
form = matcher inStream, c
skip = (not nilp form) and (form.type == 'comment') and not keepComments
break if (not skip and not nilp form) or inStream.done()
c = inStream.peek()
null
form
# readForms assumes that the string provided contains zero or more
# forms. As such, it always returns a list of zero or more forms.
# IO -> (Form* | Error)
readForms = (inStream) ->
inStream = if inStream instanceof Source then inStream else new Source inStream
return nil if inStream.done()
# IO -> (FORM*, IO) | Error
[line, column] = inStream.position()
readEach = (inStream) ->
obj = read inStream, true, null, false
return nil if (nilp obj)
return obj if obj.type == 'error'
cons obj, readEach inStream
obj = readEach inStream
if obj.type == 'error' then obj else new Node "list", obj, line, column
exports.read = read
exports.readForms = readForms
exports.Node = Node
exports.Symbol = Symbol