Nim: step1

1 files changed, 97 insertions, 0 deletions

diff --git a/nim/reader.nim b/nim/reader.nim
new file mode 100644
index 0000000..c8f9096
--- /dev/null
+++ b/nim/reader.nim
@@ -0,0 +1,97 @@
+import nre, optional_t, strutils, types
+
+var
+  tokenRE = re"""[\s,]*(~@|[\[\]{}()'`~^@]|"(?:\\.|[^\\"])*"|;.*|[^\s\[\]{}('"`,;)]*)"""
+  intRE   = re"-?[0-9]+$"
+
+type 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):
+    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
+  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)
+  r.read_form