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import nre, optional_t, strutils, types
let
tokenRE = re"""[\s,]*(~@|[\[\]{}()'`~^@]|"(?:\\.|[^\\"])*"|;.*|[^\s\[\]{}('"`,;)]*)"""
intRE = re"-?[0-9]+$"
type
Blank* = object of Exception
Reader = object
tokens: seq[string]
position: int
proc next(r: var Reader): string =
if r.position >= r.tokens.len:
result = nil
else:
result = r.tokens[r.position]
inc r.position
proc peek(r: Reader): string =
if r.position >= r.tokens.len: nil
else: r.tokens[r.position]
proc tokenize(str: string): seq[string] =
result = @[]
for match in str.findIter(tokenRE):
if match.captures[0][0] != ';':
result.add match.captures[0]
proc read_form(r: var Reader): MalType
proc read_seq(r: var Reader, fr, to: string): seq[MalType] =
result = @[]
var t = r.next
if t != fr: raise newException(ValueError, "expected '" & fr & "'")
t = r.peek
while t != to:
if t == nil: raise newException(ValueError, "expected '" & to & "', got EOF")
result.add r.read_form
t = r.peek
discard r.next
proc read_list(r: var Reader): MalType =
result = list r.read_seq("(", ")")
proc read_vector(r: var Reader): MalType =
result = vector r.read_seq("[", "]")
proc read_hash_map(r: var Reader): MalType =
result = hash_map r.read_seq("{", "}")
proc read_atom(r: var Reader): MalType =
let t = r.next
if t.match(intRE): number t.parseInt
elif t[0] == '"': str t[1 .. <t.high].replace("\\\"", "\"")
elif t[0] == ':': keyword t[1 .. t.high]
elif t == "nil": nilObj
elif t == "true": trueObj
elif t == "false": falseObj
else: symbol t
proc read_form(r: var Reader): MalType =
if r.peek[0] == ';':
discard r.next
return nilObj
case r.peek
of "'":
discard r.next
result = list(symbol "quote", r.read_form)
of "`":
discard r.next
result = list(symbol "quasiquote", r.read_form)
of "~":
discard r.next
result = list(symbol "unquote", r.read_form)
of "~@":
discard r.next
result = list(symbol "splice-unquote", r.read_form)
of "^":
discard r.next
let meta = r.read_form
result = list(symbol "with-meta", r.read_form, meta)
of "@":
discard r.next
result = list(symbol "deref", r.read_form)
# list
of "(": result = r.read_list
of ")": raise newException(ValueError, "unexpected ')'")
# vector
of "[": result = r.read_vector
of "]": raise newException(ValueError, "unexpected ']'")
# hash-map
of "{": result = r.read_hash_map
of "}": raise newException(ValueError, "unexpected '}'")
# atom
else: result = r.read_atom
proc read_str*(str: string): MalType =
var r = Reader(tokens: str.tokenize)
if r.tokens.len == 0:
raise newException(Blank, "Blank line")
r.read_form
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