got rid of some arcane module names

compiler/c2nim/c2nim.nim

@@ -8,7 +8,7 @@
 #
 
 import 
-  strutils, os, times, parseopt, llstream, ast, rnimsyn, options, msgs,
+  strutils, os, times, parseopt, llstream, ast, renderer, options, msgs,
   clex, cparse
 
 const

compiler/c2nim/cparse.nim

@@ -14,7 +14,7 @@
 # XXX cleanup of declaration handling.
 
 import 
-  os, llstream, rnimsyn, clex, idents, strutils, pegs, ast, astalgo, msgs,
+  os, llstream, renderer, clex, idents, strutils, pegs, ast, astalgo, msgs,
   options, strtabs
 
 type 

compiler/cgen.nim

@@ -14,7 +14,7 @@ import
   ast, astalgo, strutils, nhashes, trees, platform, magicsys, extccomp,
   options, 
   nversion, nimsets, msgs, crc, bitsets, idents, lists, types, ccgutils, os, 
-  times, ropes, math, passes, rodread, wordrecg, rnimsyn, treetab, cgmeth,
+  times, ropes, math, passes, rodread, wordrecg, treetab, cgmeth,
   rodutils
 
 when options.hasTinyCBackend:

compiler/cgmeth.nim

@@ -10,7 +10,7 @@
 ## This module implements code generation for multi methods.
 
 import 
-  options, ast, astalgo, msgs, idents, rnimsyn, types, magicsys
+  options, ast, astalgo, msgs, idents, renderer, types, magicsys
 
 proc genConv(n: PNode, d: PType, downcast: bool): PNode = 
   var 

compiler/docgen.nim

@@ -13,7 +13,7 @@
 
 import 
   ast, astalgo, strutils, nhashes, options, nversion, msgs, os, ropes, idents, 
-  wordrecg, math, syntaxes, rnimsyn, scanner, rst, times, highlite
+  wordrecg, math, syntaxes, renderer, lexer, rst, times, highlite
 
 proc CommandDoc*(filename: string)
 proc CommandRst2Html*(filename: string)

compiler/ecmasgen.nim

@@ -14,7 +14,7 @@
 import 
   ast, astalgo, strutils, nhashes, trees, platform, magicsys, extccomp,
   options, nversion, nimsets, msgs, crc, bitsets, idents, lists, types, os,
-  times, ropes, math, passes, ccgutils, wordrecg, rnimsyn, rodread, rodutils
+  times, ropes, math, passes, ccgutils, wordrecg, renderer, rodread, rodutils
 
 proc ecmasgenPass*(): TPass
 # implementation

compiler/evals.nim

@@ -15,7 +15,7 @@
 
 import 
   strutils, magicsys, lists, options, ast, astalgo, trees, treetab, nimsets, 
-  msgs, os, condsyms, idents, rnimsyn, types, passes, semfold
+  msgs, os, condsyms, idents, renderer, types, passes, semfold
 
 type 
   PStackFrame* = ref TStackFrame

compiler/filter_tmpl.nim

@@ -11,7 +11,7 @@
 
 import 
   llstream, os, wordrecg, idents, strutils, ast, astalgo, msgs, options, 
-  rnimsyn, filters
+  renderer, filters
 
 proc filterTmpl*(stdin: PLLStream, filename: string, call: PNode): PLLStream
   # #! template(subsChar='$', metaChar='#') | standard(version="0.7.2")

compiler/filters.nim

@@ -10,7 +10,8 @@
 # This module implements Nimrod's simple filters and helpers for filters.
 
 import
-  llstream, os, wordrecg, idents, strutils, ast, astalgo, msgs, options, rnimsyn
+  llstream, os, wordrecg, idents, strutils, ast, astalgo, msgs, options, 
+  renderer
 
 proc filterReplace*(stdin: PLLStream, filename: string, call: PNode): PLLStream
 proc filterStrip*(stdin: PLLStream, filename: string, call: PNode): PLLStream

compiler/highlite.nim

@@ -12,7 +12,7 @@
 # The interface supports one language nested in another.
 
 import 
-  nhashes, options, msgs, strutils, platform, idents, lexbase, wordrecg, scanner
+  nhashes, options, msgs, strutils, platform, idents, lexbase, wordrecg, lexer
 
 type 
   TTokenClass* = enum 
@@ -154,7 +154,7 @@ proc nimNextToken(g: var TGeneralTokenizer) =
       while not (g.buf[pos] in {'\0', '\x0A', '\x0D'}): inc(pos)
     of 'a'..'z', 'A'..'Z', '_', '\x80'..'\xFF': 
       var id = ""
-      while g.buf[pos] in scanner.SymChars + {'_'}: 
+      while g.buf[pos] in lexer.SymChars + {'_'}: 
         add(id, g.buf[pos])
         inc(pos)
       if (g.buf[pos] == '\"'): 
@@ -247,9 +247,9 @@ proc nimNextToken(g: var TGeneralTokenizer) =
     of '\0': 
       g.kind = gtEof
     else: 
-      if g.buf[pos] in scanner.OpChars: 
+      if g.buf[pos] in lexer.OpChars: 
         g.kind = gtOperator
-        while g.buf[pos] in scanner.OpChars: inc(pos)
+        while g.buf[pos] in lexer.OpChars: inc(pos)
       else: 
         inc(pos)
         g.kind = gtNone
@@ -462,9 +462,9 @@ proc clikeNextToken(g: var TGeneralTokenizer, keywords: openarray[string],
     of '\0': 
       g.kind = gtEof
     else: 
-      if g.buf[pos] in scanner.OpChars: 
+      if g.buf[pos] in lexer.OpChars: 
         g.kind = gtOperator
-        while g.buf[pos] in scanner.OpChars: inc(pos)
+        while g.buf[pos] in lexer.OpChars: inc(pos)
       else:
         inc(pos)
         g.kind = gtNone

compiler/lookups.nim

@@ -10,7 +10,7 @@
 # This module implements lookup helpers.
 
 import 
-  ast, astalgo, idents, semdata, types, msgs, options, rodread, rnimsyn
+  ast, astalgo, idents, semdata, types, msgs, options, rodread, renderer
 
 type 
   TOverloadIterMode* = enum 

compiler/main.nim

@@ -11,7 +11,7 @@
 # module handling
 
 import 
-  llstream, strutils, ast, astalgo, scanner, syntaxes, rnimsyn, options, msgs, 
+  llstream, strutils, ast, astalgo, lexer, syntaxes, renderer, options, msgs, 
   os, lists, condsyms, rodread, rodwrite, ropes, trees, 
   wordrecg, sem, semdata, idents, passes, docgen, extccomp,
   cgen, ecmasgen,

compiler/nimconf.nim

@@ -10,7 +10,7 @@
 # This module handles the reading of the config file.
 
 import 
-  llstream, nversion, commands, os, strutils, msgs, platform, condsyms, scanner, 
+  llstream, nversion, commands, os, strutils, msgs, platform, condsyms, lexer, 
   options, idents, wordrecg
 
 # ---------------- configuration file parser -----------------------------

compiler/nimrod.nim

@@ -11,7 +11,7 @@ when defined(gcc) and defined(windows):
   {.link: "icons/nimrod.res".}
 
 import 
-  times, commands, scanner, condsyms, options, msgs, nversion, nimconf, ropes, 
+  times, commands, lexer, condsyms, options, msgs, nversion, nimconf, ropes, 
   extccomp, strutils, os, platform, main, parseopt
 
 when hasTinyCBackend:

compiler/nimsets.nim

@@ -10,7 +10,7 @@
 # this unit handles Nimrod sets; it implements symbolic sets
 
 import 
-  ast, astalgo, trees, nversion, msgs, platform, bitsets, types, rnimsyn
+  ast, astalgo, trees, nversion, msgs, platform, bitsets, types, renderer
 
 proc toBitSet*(s: PNode, b: var TBitSet)
   # this function is used for case statement checking:

compiler/parser.nim

@@ -15,7 +15,7 @@
 # from the grammar and how comments belong to the AST.
 
 import
-  llstream, scanner, idents, strutils, ast, msgs
+  llstream, lexer, idents, strutils, ast, msgs
 
 type 
   TParser*{.final.} = object  # a TParser object represents a module that

compiler/pas2nim/pas2nim.nim

@@ -8,7 +8,7 @@
 #
 
 import 
-  strutils, os, parseopt, llstream, ast, rnimsyn, options, msgs,
+  strutils, os, parseopt, llstream, ast, renderer, options, msgs,
   paslex, pasparse
 
 const

compiler/passes.nim

@@ -12,8 +12,8 @@
 
 import 
   strutils, lists, options, ast, astalgo, llstream, msgs, platform, os, 
-  condsyms, idents, rnimsyn, types, extccomp, math, magicsys, nversion, nimsets, 
+  condsyms, idents, renderer, types, extccomp, math, magicsys, nversion, 
-  syntaxes, times, rodread
+  nimsets, syntaxes, times, rodread
 
 type 
   TPassContext* = object of TObject # the pass's context

compiler/pendx.nim

@@ -8,16 +8,11 @@
 #
 
 import 
-  llstream, scanner, idents, strutils, ast, msgs, pnimsyn
+  llstream, lexer, parser, idents, strutils, ast, msgs
 
-proc ParseAll*(p: var TParser): PNode
+proc ParseAll*(p: var TParser): PNode = 
-proc parseTopLevelStmt*(p: var TParser): PNode
-  # implements an iterator. Returns the next top-level statement or nil if end
-  # of stream.
-# implementation
-
-proc ParseAll(p: var TParser): PNode = 
   result = nil
 
-proc parseTopLevelStmt(p: var TParser): PNode = 
+proc parseTopLevelStmt*(p: var TParser): PNode = 
   result = nil
+  

compiler/pragmas.nim

@@ -10,7 +10,7 @@
 # This module implements semantic checking for pragmas
 
 import 
-  os, platform, condsyms, ast, astalgo, idents, semdata, msgs, rnimsyn, 
+  os, platform, condsyms, ast, astalgo, idents, semdata, msgs, renderer, 
   wordrecg, ropes, options, strutils, lists, extccomp, math, magicsys, trees,
   rodread
 

compiler/renderer.nim

@@ -10,7 +10,7 @@
 # This module implements the renderer of the standard Nimrod representation.
 
 import 
-  scanner, options, idents, strutils, ast, msgs, lists
+  lexer, options, idents, strutils, ast, msgs, lists
 
 type 
   TRenderFlag* = enum 
@@ -637,7 +637,7 @@ proc gasm(g: var TSrcGen, n: PNode) =
 proc gident(g: var TSrcGen, n: PNode) = 
   var t: TTokType
   var s = atom(n)
-  if (s[0] in scanner.SymChars): 
+  if (s[0] in lexer.SymChars): 
     if (n.kind == nkIdent): 
       if (n.ident.id < ord(tokKeywordLow) - ord(tkSymbol)) or
           (n.ident.id > ord(tokKeywordHigh) - ord(tkSymbol)): 

compiler/sem.nim

@@ -10,9 +10,9 @@
 # This module implements the semantic checking pass.
 
 import
-  strutils, nhashes, lists, options, scanner, ast, astalgo, trees, treetab, 
+  strutils, nhashes, lists, options, lexer, ast, astalgo, trees, treetab, 
-  wordrecg, ropes, msgs, os, condsyms, idents, rnimsyn, types, platform, math, 
+  wordrecg, ropes, msgs, os, condsyms, idents, renderer, types, platform, math, 
-  magicsys, pnimsyn, nversion, nimsets, semdata, evals, semfold, importer, 
+  magicsys, parser, nversion, nimsets, semdata, evals, semfold, importer, 
   procfind, lookups, rodread, pragmas, passes, semtypinst, sigmatch, suggest
 
 proc semPass*(): TPass

compiler/semdata.nim

@@ -10,9 +10,9 @@
 # This module contains the data structures for the semantic checking phase.
 
 import 
-  strutils, lists, options, scanner, ast, astalgo, trees, treetab, wordrecg, 
+  strutils, lists, options, lexer, ast, astalgo, trees, treetab, wordrecg, 
-  ropes, msgs, platform, os, condsyms, idents, rnimsyn, types, extccomp, math, 
+  ropes, msgs, platform, os, condsyms, idents, renderer, types, extccomp, math, 
-  magicsys, nversion, nimsets, pnimsyn, times, passes, rodread
+  magicsys, nversion, nimsets, parser, times, passes, rodread
 
 type 
   TOptionEntry* = object of lists.TListEntry # entries to put on a

compiler/semfold.nim

@@ -12,7 +12,7 @@
 
 import 
   strutils, lists, options, ast, astalgo, trees, treetab, nimsets, times, 
-  nversion, platform, math, msgs, os, condsyms, idents, rnimsyn, types,
+  nversion, platform, math, msgs, os, condsyms, idents, renderer, types,
   commands
 
 proc getConstExpr*(m: PSym, n: PNode): PNode

compiler/sigmatch.nim

@@ -11,7 +11,7 @@
 # the call to overloaded procs, generic procs and operators.
 
 import 
-  ast, astalgo, semdata, types, msgs, rnimsyn, lookups, semtypinst, 
+  ast, astalgo, semdata, types, msgs, renderer, lookups, semtypinst, 
   magicsys
 
 type 

compiler/suggest.nim

@@ -9,7 +9,8 @@
 
 ## This file implements features required for IDE support.
 
-import scanner, idents, ast, astalgo, semdata, msgs, types, sigmatch, options
+import 
+  lexer, idents, ast, astalgo, semdata, msgs, types, sigmatch, options
 
 const
   sep = '\t'
@@ -38,7 +39,7 @@ proc SymToStr(s: PSym, isLocal: bool, section: string): string =
   result.add($ToColumn(s.info))
 
 proc filterSym(s: PSym): bool {.inline.} = 
-  result = s.name.s[0] in scanner.SymChars
+  result = s.name.s[0] in lexer.SymChars
 
 proc suggestField(s: PSym) = 
   if filterSym(s):

compiler/syntaxes.nim

@@ -10,8 +10,8 @@
 ## Implements the dispatcher for the different parsers.
 
 import 
-  strutils, llstream, ast, astalgo, idents, scanner, options, msgs, pnimsyn, 
+  strutils, llstream, ast, astalgo, idents, lexer, options, msgs, parser, 
-  pbraces, ptmplsyn, filters, rnimsyn
+  pbraces, filters, filter_tmpl, renderer
 
 type 
   TFilterKind* = enum 
@@ -54,7 +54,7 @@ proc ParseFile(filename: string): PNode =
 proc parseAll(p: var TParsers): PNode = 
   case p.skin
   of skinStandard: 
-    result = pnimsyn.parseAll(p.parser)
+    result = parser.parseAll(p.parser)
   of skinBraces: 
     result = pbraces.parseAll(p.parser)
   of skinEndX: 
@@ -65,7 +65,7 @@ proc parseAll(p: var TParsers): PNode =
 proc parseTopLevelStmt(p: var TParsers): PNode = 
   case p.skin
   of skinStandard: 
-    result = pnimsyn.parseTopLevelStmt(p.parser)
+    result = parser.parseTopLevelStmt(p.parser)
   of skinBraces: 
     result = pbraces.parseTopLevelStmt(p.parser)
   of skinEndX: 
@@ -99,7 +99,7 @@ proc parsePipe(filename: string, inputStream: PLLStream): PNode =
       while line[i] in WhiteSpace: inc(i)
       var q: TParser
       OpenParser(q, filename, LLStreamOpen(copy(line, i)))
-      result = pnimsyn.parseAll(q)
+      result = parser.parseAll(q)
       CloseParser(q)
     LLStreamClose(s)
 
@@ -167,7 +167,7 @@ proc openParsers(p: var TParsers, filename: string, inputstream: PLLStream) =
   else: s = inputStream
   case p.skin
   of skinStandard, skinBraces, skinEndX: 
-    pnimsyn.openParser(p.parser, filename, s)
+    parser.openParser(p.parser, filename, s)
   
 proc closeParsers(p: var TParsers) = 
-  pnimsyn.closeParser(p.parser)
+  parser.closeParser(p.parser)

compiler/transf.nim

@@ -18,7 +18,7 @@
 
 import 
   strutils, lists, options, ast, astalgo, trees, treetab, evals, msgs, os, 
-  idents, rnimsyn, types, passes, semfold, magicsys, cgmeth
+  idents, renderer, types, passes, semfold, magicsys, cgmeth
 
 const 
   genPrefix* = ":tmp"         # prefix for generated names

compiler/trees.nim

@@ -10,7 +10,7 @@
 # tree helper routines
 
 import 
-  ast, astalgo, scanner, msgs, strutils
+  ast, astalgo, lexer, msgs, strutils
 
 proc getMagic*(op: PNode): TMagic
 

doc/filelist.txt

@@ -9,16 +9,11 @@ nimrod          main module: parses the command line and calls
 main            implements the top-level command dispatching
 nimconf         implements the config file reader
 syntaxes        dispatcher for the different parsers and filters
-ptmplsyn        standard template filter (``#! stdtempl``)
+filter_tmpl     standard template filter (``#! stdtempl``)
 lexbase         buffer handling of the lexical analyser
-scanner         lexical analyser
+lexer           lexical analyser
-pnimsyn         Nimrod's parser
+parser          Nimrod's parser
-rnimsyn         Nimrod code renderer (AST back to its textual form)
+renderer        Nimrod code renderer (AST back to its textual form)
-
-paslex          lexer for Pascal
-pasparse        parser for Pascal; Pascal's advanced OO features are not
-                supported
-
 options         contains global and local compiler options
 ast             type definitions of the abstract syntax tree (AST) and
                 node constructors

lib/pure/collections/hashtables.nim

@@ -18,8 +18,8 @@ type
   TKeyValuePair[A, B] = tuple[slot: TSlotEnum, key: A, val: B]
   TKeyValuePairSeq[A, B] = seq[TKeyValuePair[A, B]]
   THashTable[A, B] = object of TObject
-    counter: int
     data: TKeyValuePairSeq[A, B]
+    counter: int
 
   PHashTable*[A, B] = ref THashTable[A, B] ## use this type to declare tables
 
@@ -32,12 +32,12 @@ iterator pairs*[A, B](t: PHashTable[A, B]): tuple[key: A, val: B] =
   for h in 0..high(t.data):
     if t.data[h].slot == seFilled: yield (t.data[h].key, t.data[h].val)
 
-iterator keys*[A, B](t: PHashTable[A, B]): tuple[key: A, val: B] =
+iterator keys*[A, B](t: PHashTable[A, B]): A =
   ## iterates over any key in the table `t`.
   for h in 0..high(t.data):
     if t.data[h].slot == seFilled: yield t.data[h].key
 
-iterator values*[A, B](t: PHashTable[A, B]): tuple[key: A, val: B] =
+iterator values*[A, B](t: PHashTable[A, B]): B =
   ## iterates over any value in the table `t`.
   for h in 0..high(t.data):
     if t.data[h].slot == seFilled: yield t.data[h].val
@@ -103,6 +103,7 @@ proc del*[A, B](t: PHashTable[A, B], key: A) =
   var index = RawGet(t, key)
   if index >= 0:
     t.data[index].slot = seDeleted
+    dec(t.counter)
 
 proc newHashTable*[A, B](initialSize = 64): PHashTable[A, B] =
   ## creates a new string table that is empty. `initialSize` needs to be
@@ -125,6 +126,110 @@ proc `$`*[A, B](t: PHashTable[A, B]): string =
       result.add($val)
     result.add("}")
 
+
+# ------------------------------ count tables -------------------------------
+
+const
+  deletedCount = -1
+
+type
+  TCountTable*[A] {.final.} = object
+    data: seq[tuple[key: A, val: int]]
+    counter: int
+
+proc len*[A](t: TCountTable[A]): int =
+  ## returns the number of keys in `t`.
+  result = t.counter
+
+iterator pairs*[A](t: TCountTable[A]): tuple[key: A, val: int] =
+  ## iterates over any (key, value) pair in the table `t`.
+  for h in 0..high(t.data):
+    if t.data[h].slot == seFilled: yield (t.data[h].key, t.data[h].val)
+
+iterator keys*[A](t: TCountTable[A]): A =
+  ## iterates over any key in the table `t`.
+  for h in 0..high(t.data):
+    if t.data[h].slot == seFilled: yield t.data[h].key
+
+iterator values*[A](t: TCountTable[A]): int =
+  ## iterates over any value in the table `t`.
+  for h in 0..high(t.data):
+    if t.data[h].slot == seFilled: yield t.data[h].val
+
+proc RawGet[A](t: TCountTable[A], key: A): int =
+  var h: THash = hash(key) and high(t.data) # start with real hash value
+  while t.data[h].slot != seEmpty:
+    if t.data[h].key == key and t.data[h].slot == seFilled:
+      return h
+    h = nextTry(h, high(t.data))
+  result = -1
+
+proc `[]`*[A](t: TCountTable[A], key: A): B =
+  ## retrieves the value at ``t[key]``. If `key` is not in `t`,
+  ## default empty value for the type `B` is returned
+  ## and no exception is raised. One can check with ``hasKey`` whether the key
+  ## exists.
+  var index = RawGet(t, key)
+  if index >= 0: result = t.data[index].val
+
+proc hasKey*[A](t: TCountTable[A], key: A): bool =
+  ## returns true iff `key` is in the table `t`.
+  result = rawGet(t, key) >= 0
+
+proc RawInsert[A](t: TCountTable[A], data: var TKeyValuePairSeq[A, B],
+                     key: A, val: int) =
+  var h: THash = hash(key) and high(data)
+  while data[h].slot == seFilled:
+    h = nextTry(h, high(data))
+  data[h].key = key
+  data[h].val = val
+  data[h].slot = seFilled
+
+proc Enlarge[A](t: TCountTable[A]) =
+  var n: TKeyValuePairSeq[A, B]
+  newSeq(n, len(t.data) * growthFactor)
+  for i in countup(0, high(t.data)):
+    if t.data[i].slot == seFilled: RawInsert(t, n, t.data[i].key, t.data[i].val)
+  swap(t.data, n)
+
+proc `[]=`*[A](t: TCountTable[A], key: A, val: int) =
+  ## puts a (key, value)-pair into `t`.
+  var index = RawGet(t, key)
+  if index >= 0:
+    t.data[index].val = val
+  else:
+    if mustRehash(len(t.data), t.counter): Enlarge(t)
+    RawInsert(t, t.data, key, val)
+    inc(t.counter)
+
+proc del*[A](t: TCountTable[A], key: A) =
+  ## deletes `key` from hash table `t`.
+  var index = RawGet(t, key)
+  if index >= 0:
+    t.data[index].slot = seDeleted
+
+proc newHashTable*[A, B](initialSize = 64): PHashTable[A, B] =
+  ## creates a new string table that is empty. `initialSize` needs to be
+  ## a power of two.
+  assert isPowerOfTwo(initialSize)
+  new(result)
+  result.counter = 0
+  newSeq(result.data, initialSize)
+
+proc `$`*[A](t: TCountTable[A]): string =
+  ## The `$` operator for string tables.
+  if t.len == 0:
+    result = "{:}"
+  else:
+    result = "{"
+    for key, val in pairs(t):
+      if result.len > 1: result.add(", ")
+      result.add($key)
+      result.add(": ")
+      result.add($val)
+    result.add("}")
+
+
 when isMainModule:
   var table = newHashTable[string, float]()
   table["test"] = 1.2345

lib/pure/collections/lists.nim

@@ -0,0 +1,155 @@
+#
+#
+#            Nimrod's Runtime Library
+#        (c) Copyright 2011 Andreas Rumpf
+#
+#    See the file "copying.txt", included in this
+#    distribution, for details about the copyright.
+#
+
+## Implementation of singly and doubly linked lists. Because it makes no sense
+## to do so, the 'next' and 'prev' pointers are not hidden from you and can
+## be manipulated directly for efficiency.
+
+type
+  TDoublyLinkedNode[T] {.pure, final.} = object
+    next*, prev*: ref TDoublyLinkedNode[T]
+    value*: T
+  PDoublyLinkedNode*[T] = ref TDoublyLinkedNode[T]
+
+  TSinglyLinkedNode[T] {.pure, final.} = object
+    next*: ref TSinglyLinkedNode[T]
+    value*: T
+  PSinglyLinkedNode*[T] = ref TSinglyLinkedNode[T]
+
+proc newDoublyLinkedNode*[T](value: T): PDoublyLinkedNode[T] =
+  ## creates a new doubly linked node with the given `value`.
+  new(result)
+  result.value = value
+
+proc newSinglyLinkedNode*[T](value: T): PSinglyLinkedNode[T] =
+  ## creates a new singly linked node with the given `value`.
+  new(result)
+  result.value = value
+
+iterator items*[T](n: PDoublyLinkedNode[T]): T = 
+  ## yields every value of `x`.
+  var it = n
+  while it != nil:
+    yield it.value
+    it = it.next
+
+iterator items*[T](n: PSinglyLinkedNode[T]): T = 
+  ## yields every value of `x`.
+  var it = n
+  while it != nil:
+    yield it.value
+    it = it.next
+
+iterator nodes*[T](n: PSinglyLinkedNode[T]): PSinglyLinkedNode[T] = 
+  ## iterates over every node of `x`. Removing the current node from the
+  ## list during traversal is supported.
+  var it = n
+  while it != nil:
+    var nxt = it.next
+    yield it
+    it = nxt
+
+iterator nodes*[T](n: PDoublyLinkedNode[T]): PDoublyLinkedNode[T] = 
+  ## iterates over every node of `x`. Removing the current node from the
+  ## list during traversal is supported.
+  var it = n
+  while it != nil:
+    var nxt = it.next
+    yield it
+    it = nxt
+
+proc `$`*[list: PSinglyLinkedNode|PDoublyLinkedNode](n: list): string = 
+  ## turns a list into its string representation.
+  result = "["
+  for x in nodes(n):
+    if result.len > 1: result.add(", ")
+    result.add($x.value)
+  result.add("]")
+
+proc find*[list: PSinglyLinkedNode|PDoublyLinkedNode, T](
+           n: list, value: T): list = 
+  ## searches in the list for a value. Returns nil if the value does not
+  ## exist.
+  for x in nodes(n):
+    if x.value == value: return x
+
+proc contains*[list: PSinglyLinkedNode|PDoublyLinkedNode, T](
+           n: list, value: T): list = 
+  ## searches in the list for a value. Returns false if the value does not
+  ## exist, true otherwise.
+  for x in nodes(n):
+    if x.value == value: return true
+
+proc prepend*[T](head: var PSinglyLinkedNode[T], 
+                 toAdd: PSinglyLinkedNode[T]) {.inline.} = 
+  ## prepends a node to `head`. Efficiency: O(1).
+  toAdd.next = head
+  head = toAdd
+
+proc prepend*[T](head: var PSinglyLinkedNode[T], x: T) {.inline.} = 
+  ## creates a new node with the value `x` and prepends that node to `head`.
+  ## Efficiency: O(1).
+  preprend(head, newSinglyLinkedNode(x))
+
+proc append*[T](head: var PSinglyLinkedNode[T], 
+                toAdd: PSinglyLinkedNode[T]) = 
+  ## appends a node to `head`. Efficiency: O(n).
+  if head == nil:
+    head = toAdd
+  else:
+    var it = head
+    while it.next != nil: it = it.next
+    it.next = toAdd
+
+proc append*[T](head: var PSinglyLinkedNode[T], x: T) {.inline.} = 
+  ## creates a new node with the value `x` and appends that node to `head`.
+  ## Efficiency: O(n).
+  append(head, newSinglyLinkedNode(x))
+
+
+proc prepend*[T](head: var PDoublyLinkedNode[T], 
+                 toAdd: PDoublyLinkedNode[T]) {.inline.} = 
+  ## prepends a node to `head`. Efficiency: O(1).
+  if head == nil:
+    head = toAdd
+    # head.prev stores the last node:
+    head.prev = toAdd
+  else:
+    toAdd.next = head
+    toAdd.prev = head.prev # copy pointer to last element
+    head.prev = toAdd
+    head = toAdd
+
+proc prepend*[T](head: var PDoublyLinkedNode[T], x: T) {.inline.} = 
+  ## creates a new node with the value `x` and prepends that node to `head`.
+  ## Efficiency: O(1).
+  preprend(head, newDoublyLinkedNode(x))
+
+proc append*[T](head: var PDoublyLinkedNode[T], 
+                toAdd: PDoublyLinkedNode[T]) {.inline.} = 
+  ## appends a node to `head`. Efficiency: O(1).
+  if head == nil:
+    head = toAdd
+    # head.prev stores the last node:
+    head.prev = toAdd
+  else:
+    var last = head.prev
+    assert last.next == nil
+    last.next = toAdd
+    toAdd.prev = last
+    head.prev = toAdd # new last element
+
+proc append*[T](head: var PDoublyLinkedNode[T], x: T) {.inline.} = 
+  ## creates a new node with the value `x` and appends that node to `head`.
+  ## Efficiency: O(1).
+  append(head, newDoublyLinkedNode(x))
+
+
+
+