Scala Forum

StackOverflow beim compilieren? (3 replies)

2010-09-05T16:06:20+02:00

Servus,

beim compilieren mit Maven bekomme ich eine StackOverflow-Exception. Leider kann ich den Ort nicht zu 100% ausmachen, aber ich denke mal das es an dem folgenden Codestück liegt.

Wie kann ich den Überlauf verhindern?
Die Arrays enthalten jetzt nicht so viel Elemente. Wieso wird hier bereits ein Überlauf produziert?

Compiling 133 source files to... at 1283695019242
java.lang.reflect.InvocationTargetException
        at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
        at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
        at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
        at java.lang.reflect.Method.invoke(Method.java:597)
        at org_scala_tools_maven_executions.MainHelper.runMain(MainHelper.java:151)
        at org_scala_tools_maven_executions.MainWithArgsInFile.main(MainWithArgsInFile.java:26)
[ERROR]Caused by: java.lang.StackOverflowError
        at scala.tools.nsc.typechecker.Typers$Typer.gd9$1(Typers.scala:785)
        at scala.tools.nsc.typechecker.Typers$Typer.adapt(Typers.scala:771)
        at scala.tools.nsc.typechecker.Typers$Typer.typed(Typers.scala:4083)
        at scala.tools.nsc.typechecker.Typers$Typer.typedTypeConstructor(Typers.scala:4189)
        at scala.tools.nsc.typechecker.Typers$Typer.typedTypeConstructor(Typers.scala:4212)
        at scala.tools.nsc.typechecker.Typers$Typer.typedNew$1(Typers.scala:3140)
        at scala.tools.nsc.typechecker.Typers$Typer.typed1(Typers.scala:3849)
        at scala.tools.nsc.typechecker.Typers$Typer.typed(Typers.scala:4078)
        at scala.tools.nsc.typechecker.Typers$Typer.typedQualifier(Typers.scala:4145)
        at scala.tools.nsc.typechecker.Typers$Typer.typedQualifier(Typers.scala:4151)
        at scala.tools.nsc.typechecker.Typers$Typer.typed1(Typers.scala:3964)
        at scala.tools.nsc.typechecker.Typers$Typer.typed(Typers.scala:4078)
        at scala.tools.nsc.typechecker.Typers$Typer.typedOperator(Typers.scala:4157)
        at scala.tools.nsc.typechecker.RefChecks$RefCheckTransformer.toConstructor(RefChecks.scala:797)
        at scala.tools.nsc.typechecker.RefChecks$RefCheckTransformer.transformCaseApply(RefChecks.scala:1008)
        at scala.tools.nsc.typechecker.RefChecks$RefCheckTransformer.transform(RefChecks.scala:1146)
        at scala.tools.nsc.ast.Trees$Transformer.transform(Trees.scala:804)
        at scala.tools.nsc.typechecker.RefChecks$RefCheckTransformer.transform(RefChecks.scala:1183)
        at scala.tools.nsc.ast.Trees$Transformer$$anonfun$transformTrees$1.apply(Trees.scala:838)
        at scala.tools.nsc.ast.Trees$Transformer$$anonfun$transformTrees$1.apply(Trees.scala:838)
        at scala.collection.immutable.List.loop$1(List.scala:115)
        at scala.collection.immutable.List.mapConserve(List.scala:132)
        at scala.collection.immutable.List.loop$1(List.scala:119)
        at scala.collection.immutable.List.mapConserve(List.scala:132)
        at scala.collection.immutable.List.loop$1(List.scala:119)
        at scala.collection.immutable.List.mapConserve(List.scala:132)
        at scala.collection.immutable.List.loop$1(List.scala:119)
        at scala.collection.immutable.List.mapConserve(List.scala:132)
        at scala.collection.immutable.List.loop$1(List.scala:119)
        at scala.collection.immutable.List.mapConserve(List.scala:132)
        at scala.collection.immutable.List.loop$1(List.scala:119)
        at scala.collection.immutable.List.mapConserve(List.scala:132)
        at scala.collection.immutable.List.loop$1(List.scala:119)
        at scala.collection.immutable.List.mapConserve(List.scala:132)
        at scala.collection.immutable.List.loop$1(List.scala:119)
        at scala.collection.immutable.List.mapConserve(List.scala:132)
        at scala.collection.immutable.List.loop$1(List.scala:119)
        at scala.collection.immutable.List.mapConserve(List.scala:132)
        at scala.collection.immutable.List.loop$1(List.scala:119)
        at scala.collection.immutable.List.mapConserve(List.scala:132)
        at scala.collection.immutable.List.loop$1(List.scala:119)
....

Im Orginal sind mehrere Zeilen dieser Form (Array von (Double, Double) oder (Double, Double, Double, Double)) und Länge enthalten.

Language: Scala
object CIE {
  // ....
 
  /**
   * Standard illuminants: CIE Illuminant D65
   *
   */
  private[this] lazy val Illuminantd65 = Array[(Double, Double)] (
    (300, 0.034100),
    (301, 0.360140),
    (302, 0.686180),
    (303, 1.012220),
    (304, 1.338260),
    (305, 1.664300),
    (306, 1.990340),
    (307, 2.316380),
    (308, 2.642420),
    (309, 2.968460),
    (310, 3.294500),
    (311, 4.988650),
    (312, 6.682800),
    (313, 8.376950),
    (314, 10.071100),
    (315, 11.765200),
    (316, 13.459400),
    (317, 15.153500),
    (318, 16.847700),
    (319, 18.541800),
    (320, 20.236000),
    (321, 21.917700),
    (322, 23.599500),
    (323, 25.281200),
    (324, 26.963000),
    (325, 28.644700),
    (326, 30.326500),
    (327, 32.008200),
    (328, 33.690000),
    (329, 35.371700),
    (330, 37.053500),
    (331, 37.343000),
    (332, 37.632600),
    (333, 37.922100),
    (334, 38.211600),
    (335, 38.501100),
    (336, 38.790700),
    (337, 39.080200),
    (338, 39.369700),
    (339, 39.659300),
    (340, 39.948800),
    (341, 40.445100),
    (342, 40.941400),
    (343, 41.437700),
    (344, 41.934000),
    (345, 42.430200),
    (346, 42.926500),
    (347, 43.422800),
    (348, 43.919100),
    (349, 44.415400),
    (350, 44.911700),
    (351, 45.084400),
    (352, 45.257000),
    (353, 45.429700),
    (354, 45.602300),
    (355, 45.775000),
    (356, 45.947700),
    (357, 46.120300),
    (358, 46.293000),
    (359, 46.465600),
    (360, 46.638300),
    (361, 47.183400),
    (362, 47.728500),
    (363, 48.273500),
    (364, 48.818600),
    (365, 49.363700),
    (366, 49.908800),
    (367, 50.453900),
    (368, 50.998900),
    (369, 51.544000),
    (370, 52.089100),
    (371, 51.877700),
    (372, 51.666400),
    (373, 51.455000),
    (374, 51.243700),
    (375, 51.032300),
    (376, 50.820900),
    (377, 50.609600),
    (378, 50.398200),
    (379, 50.186900),
    (380, 49.975500),
    (381, 50.442800),
    (382, 50.910000),
    (383, 51.377300),
    (384, 51.844600),
    (385, 52.311800),
    (386, 52.779100),
    (387, 53.246400),
    (388, 53.713700),
    (389, 54.180900),
    (390, 54.648200),
    (391, 57.458900),
    (392, 60.269500),
    (393, 63.080200),
    (394, 65.890900),
    (395, 68.701500),
    (396, 71.512200),
    (397, 74.322900),
    (398, 77.133600),
    (399, 79.944200),
    (400, 82.754900),
    (401, 83.628000),
    (402, 84.501100),
    (403, 85.374200),
    (404, 86.247300),
    (405, 87.120400),
    (406, 87.993600),
    (407, 88.866700),
    (408, 89.739800),
    (409, 90.612900),
    (410, 91.486000),
    (411, 91.680600),
    (412, 91.875200),
    (413, 92.069700),
    (414, 92.264300),
    (415, 92.458900),
    (416, 92.653500),
    (417, 92.848100),
    (418, 93.042600),
    (419, 93.237200),
    (420, 93.431800),
    (421, 92.756800),
    (422, 92.081900),
    (423, 91.406900),
    (424, 90.732000),
    (425, 90.057000),
    (426, 89.382100),
    (427, 88.707100),
    (428, 88.032200),
    (429, 87.357200),
    (430, 86.682300),
    (431, 88.500600),
    (432, 90.318800),
    (433, 92.137100),
    (434, 93.955400),
    (435, 95.773600),
    (436, 97.591900),
    (437, 99.410200),
    (438, 101.228000),
    (439, 103.047000),
    (440, 104.865000),
    (441, 106.079000),
    (442, 107.294000),
    (443, 108.508000),
    (444, 109.722000),
    (445, 110.936000),
    (446, 112.151000),
    (447, 113.365000),
    (448, 114.579000),
    (449, 115.794000),
    (450, 117.008000),
    (451, 117.088000),
    (452, 117.169000),
    (453, 117.249000),
    (454, 117.330000),
    (455, 117.410000),
    (456, 117.490000),
    (457, 117.571000),
    (458, 117.651000),
    (459, 117.732000),
    (460, 117.812000),
    (461, 117.517000),
    (462, 117.222000),
    (463, 116.927000),
    (464, 116.632000),
    (465, 116.336000),
    (466, 116.041000),
    (467, 115.746000),
    (468, 115.451000),
    (469, 115.156000),
    (470, 114.861000),
    (471, 114.967000),
    (472, 115.073000),
    (473, 115.180000),
    (474, 115.286000),
    (475, 115.392000),
    (476, 115.498000),
    (477, 115.604000),
    (478, 115.711000),
    (479, 115.817000),
    (480, 115.923000),
    (481, 115.212000),
    (482, 114.501000),
    (483, 113.789000),
    (484, 113.078000),
    (485, 112.367000),
    (486, 111.656000),
    (487, 110.945000),
    (488, 110.233000),
    (489, 109.522000),
    (490, 108.811000),
    (491, 108.865000),
    (492, 108.920000),
    (493, 108.974000),
    (494, 109.028000),
    (495, 109.082000),
    (496, 109.137000),
    (497, 109.191000),
    (498, 109.245000),
    (499, 109.300000),
    (500, 109.354000),
    (501, 109.199000),
    (502, 109.044000),
    (503, 108.888000),
    (504, 108.733000),
    (505, 108.578000),
    (506, 108.423000),
    (507, 108.268000),
    (508, 108.112000),
    (509, 107.957000),
    (510, 107.802000),
    (511, 107.501000),
    (512, 107.200000),
    (513, 106.898000),
    (514, 106.597000),
    (515, 106.296000),
    (516, 105.995000),
    (517, 105.694000),
    (518, 105.392000),
    (519, 105.091000),
    (520, 104.790000),
    (521, 105.080000),
    (522, 105.370000),
    (523, 105.660000),
    (524, 105.950000),
    (525, 106.239000),
    (526, 106.529000),
    (527, 106.819000),
    (528, 107.109000),
    (529, 107.399000),
    (530, 107.689000),
    (531, 107.361000),
    (532, 107.032000),
    (533, 106.704000),
    (534, 106.375000),
    (535, 106.047000),
    (536, 105.719000),
    (537, 105.390000),
    (538, 105.062000),
    (539, 104.733000),
    (540, 104.405000),
    (541, 104.369000),
    (542, 104.333000),
    (543, 104.297000),
    (544, 104.261000),
    (545, 104.225000),
    (546, 104.190000),
    (547, 104.154000),
    (548, 104.118000),
    (549, 104.082000),
    (550, 104.046000),
    (551, 103.641000),
    (552, 103.237000),
    (553, 102.832000),
    (554, 102.428000),
    (555, 102.023000),
    (556, 101.618000),
    (557, 101.214000),
    (558, 100.809000),
    (559, 100.405000),
    (560, 100.000000),
    (561, 99.633400),
    (562, 99.266800),
    (563, 98.900300),
    (564, 98.533700),
    (565, 98.167100),
    (566, 97.800500),
    (567, 97.433900),
    (568, 97.067400),
    (569, 96.700800),
    (570, 96.334200),
    (571, 96.279600),
    (572, 96.225000),
    (573, 96.170300),
    (574, 96.115700),
    (575, 96.061100),
    (576, 96.006500),
    (577, 95.951900),
    (578, 95.897200),
    (579, 95.842600),
    (580, 95.788000),
    (581, 95.077800),
    (582, 94.367500),
    (583, 93.657300),
    (584, 92.947000),
    (585, 92.236800),
    (586, 91.526600),
    (587, 90.816300),
    (588, 90.106100),
    (589, 89.395800),
    (590, 88.685600),
    (591, 88.817700),
    (592, 88.949700),
    (593, 89.081800),
    (594, 89.213800),
    (595, 89.345900),
    (596, 89.478000),
    (597, 89.610000),
    (598, 89.742100),
    (599, 89.874100),
    (600, 90.006200),
    (601, 89.965500),
    (602, 89.924800),
    (603, 89.884100),
    (604, 89.843400),
    (605, 89.802600),
    (606, 89.761900),
    (607, 89.721200),
    (608, 89.680500),
    (609, 89.639800),
    (610, 89.599100),
    (611, 89.409100),
    (612, 89.219000),
    (613, 89.029000),
    (614, 88.838900),
    (615, 88.648900),
    (616, 88.458900),
    (617, 88.268800),
    (618, 88.078800),
    (619, 87.888700),
    (620, 87.698700),
    (621, 87.257700),
    (622, 86.816700),
    (623, 86.375700),
    (624, 85.934700),
    (625, 85.493600),
    (626, 85.052600),
    (627, 84.611600),
    (628, 84.170600),
    (629, 83.729600),
    (630, 83.288600),
    (631, 83.329700),
    (632, 83.370700),
    (633, 83.411800),
    (634, 83.452800),
    (635, 83.493900),
    (636, 83.535000),
    (637, 83.576000),
    (638, 83.617100),
    (639, 83.658100),
    (640, 83.699200),
    (641, 83.332000),
    (642, 82.964700),
    (643, 82.597500),
    (644, 82.230200),
    (645, 81.863000),
    (646, 81.495800),
    (647, 81.128500),
    (648, 80.761300),
    (649, 80.394000),
    (650, 80.026800),
    (651, 80.045600),
    (652, 80.064400),
    (653, 80.083100),
    (654, 80.101900),
    (655, 80.120700),
    (656, 80.139500),
    (657, 80.158300),
    (658, 80.177000),
    (659, 80.195800),
    (660, 80.214600),
    (661, 80.420900),
    (662, 80.627200),
    (663, 80.833600),
    (664, 81.039900),
    (665, 81.246200),
    (666, 81.452500),
    (667, 81.658800),
    (668, 81.865200),
    (669, 82.071500),
    (670, 82.277800),
    (671, 81.878400),
    (672, 81.479100),
    (673, 81.079700),
    (674, 80.680400),
    (675, 80.281000),
    (676, 79.881600),
    (677, 79.482300),
    (678, 79.082900),
    (679, 78.683600),
    (680, 78.284200),
    (681, 77.427900),
    (682, 76.571600),
    (683, 75.715300),
    (684, 74.859000),
    (685, 74.002700),
    (686, 73.146500),
    (687, 72.290200),
    (688, 71.433900),
    (689, 70.577600),
    (690, 69.721300),
    (691, 69.910100),
    (692, 70.098900),
    (693, 70.287600),
    (694, 70.476400),
    (695, 70.665200),
    (696, 70.854000),
    (697, 71.042800),
    (698, 71.231500),
    (699, 71.420300),
    (700, 71.609100),
    (701, 71.883100),
    (702, 72.157100),
    (703, 72.431100),
    (704, 72.705100),
    (705, 72.979000),
    (706, 73.253000),
    (707, 73.527000),
    (708, 73.801000),
    (709, 74.075000),
    (710, 74.349000),
    (711, 73.074500),
    (712, 71.800000),
    (713, 70.525500),
    (714, 69.251000),
    (715, 67.976500),
    (716, 66.702000),
    (717, 65.427500),
    (718, 64.153000),
    (719, 62.878500),
    (720, 61.604000),
    (721, 62.432200),
    (722, 63.260300),
    (723, 64.088500),
    (724, 64.916600),
    (725, 65.744800),
    (726, 66.573000),
    (727, 67.401100),
    (728, 68.229300),
    (729, 69.057400),
    (730, 69.885600),
    (731, 70.405700),
    (732, 70.925900),
    (733, 71.446000),
    (734, 71.966200),
    (735, 72.486300),
    (736, 73.006400),
    (737, 73.526600),
    (738, 74.046700),
    (739, 74.566900),
    (740, 75.087000),
    (741, 73.937600),
    (742, 72.788100),
    (743, 71.638700),
    (744, 70.489300),
    (745, 69.339800),
    (746, 68.190400),
    (747, 67.041000),
    (748, 65.891600),
    (749, 64.742100),
    (750, 63.592700),
    (751, 61.875200),
    (752, 60.157800),
    (753, 58.440300),
    (754, 56.722900),
    (755, 55.005400),
    (756, 53.288000),
    (757, 51.570500),
    (758, 49.853100),
    (759, 48.135600),
    (760, 46.418200),
    (761, 48.456900),
    (762, 50.495600),
    (763, 52.534400),
    (764, 54.573100),
    (765, 56.611800),
    (766, 58.650500),
    (767, 60.689200),
    (768, 62.728000),
    (769, 64.766700),
    (770, 66.805400),
    (771, 66.463100),
    (772, 66.120900),
    (773, 65.778600),
    (774, 65.436400),
    (775, 65.094100),
    (776, 64.751800),
    (777, 64.409600),
    (778, 64.067300),
    (779, 63.725100),
    (780, 63.382800),
    (781, 63.474900),
    (782, 63.567000),
    (783, 63.659200),
    (784, 63.751300),
    (785, 63.843400),
    (786, 63.935500),
    (787, 64.027600),
    (788, 64.119800),
    (789, 64.211900),
    (790, 64.304000),
    (791, 63.818800),
    (792, 63.333600),
    (793, 62.848400),
    (794, 62.363200),
    (795, 61.877900),
    (796, 61.392700),
    (797, 60.907500),
    (798, 60.422300),
    (799, 59.937100),
    (800, 59.451900),
    (801, 58.702600),
    (802, 57.953300),
    (803, 57.204000),
    (804, 56.454700),
    (805, 55.705400),
    (806, 54.956200),
    (807, 54.206900),
    (808, 53.457600),
    (809, 52.708300),
    (810, 51.959000),
    (811, 52.507200),
    (812, 53.055300),
    (813, 53.603500),
    (814, 54.151600),
    (815, 54.699800),
    (816, 55.248000),
    (817, 55.796100),
    (818, 56.344300),
    (819, 56.892400),
    (820, 57.440600),
    (821, 57.727800),
    (822, 58.015000),
    (823, 58.302200),
    (824, 58.589400),
    (825, 58.876500),
    (826, 59.163700),
    (827, 59.450900),
    (828, 59.738100),
    (829, 60.025300),
    (830, 60.312500)
  )
 
  lazy val StandardIlluminants_CIE_D65:CoefficientSpectrum =
    new SampledSpectrum(Illuminantd65.map{i => i._1.toDouble}, Illuminantd65.map{i => i._2},
                        CIE_Interpolation_Mode,
                        100)
}

closing a dialog; graphics (no replies)

2010-09-05T11:39:47+02:00

Hi,

how do I close a SimpleSwingApplication or a Frame? dispose() and close() have no effect.

How can I set graphics in a Frame? What is the name of the class?

Extention of Enumeration (5 replies)

2010-09-05T09:34:55+02:00

Hi
Is it possible to add some extra attributes or methods to a scala enum (using the Enumeration class) or not?
THX AG WW

Scala Swing Grafiken einfügen (3 replies)

2010-09-04T11:18:14+02:00

Hallo,

ich habe schon gegoogelt, finde aber nur Themen für Java Swing.

Wie füge ich Bilder in einem Scala Swing Dialog ein?

Ich denke ich mache dies mit

new Label()

und da muss ich dann das Bild übergeben. Aber wie bzw. wie heißt die Klasse dafür?

Translations of Scala Books (no replies)

2010-09-02T22:02:00+02:00

Hello everybody,

Do you know if one of the existing books on scala will be translated in other languages than english ?

I am a french student and I am currently reading the online writing "Programming Scala" of Alex Payne.

However, I prefer reading books in french and I would like to know if one of the scala books will be translated in french, especially "Programming in Scala: A Comprehensive Step-by-step Guide" of Martin Odersky, Lex Spoon, Bill Venners.

Thanks for reply

Klassen und Typen (5 replies)

2010-09-01T21:44:39+02:00

Hallo,

Language: Scala
class Test[T](a:T, b:T) {
  // ...
  def calc = {
    val c = a + b * a
    c
  }
}
 
class PossibleType {
 
  def +(v:PossibleType) = ...
  def * ....
}

Jetzt soll das ganze für T gleich
1. Test[Double], Test[Int], ...
2. Test[PossibleType], Test[...
funktionieren.

Bei 2. sehe ich kein Problem. z.B. würde sich ein trait anbieten. Aber wie schaffe ich es, dass z.B. auch Double geht?

Gruß,
Thomas

Again Euler, this time Id 14 (7 replies)

2010-08-31T11:16:55+02:00

Hi.

I'm currently stuck at Euler 14.
The algorithm I believed is't difficult.
This I use to calculate the longest chain:

Language: Scala
def largestChain(end: Long): List[Long] = {
    var maxChainSize: Long = 0
    var maxChain: List[Long] = Nil
    (1l until end).foreach {n =>
      val chain = calcChain(n)
      val chainSize = chain.size
      if(chainSize > maxChainSize && chain.head == 1) {
	maxChainSize = chainSize
	maxChain = chain
      }
    }
    maxChain
  }
 
  def calcChain(n: Long): List[Long] = {
    def _calcChain(chain: List[Long]): List[Long] = {
      val head = chain.head
      if(head == 1) return chain
      else if(head%2 == 0) return _calcChain(head/2 :: chain)
      else return _calcChain(head*3+1 :: chain)
    }
    _calcChain(n :: Nil)
  }

When run with 1000000 it calculates the largest chain of 525 elements for n = 837799.
But that doesn't seem to be the right value. Eulers web page doesn't accept it.
Can't find the problem.
Any idea?

Manfred

Type missmatch (7 replies)

2010-08-30T10:51:02+02:00

Hello all together,

I need to implement the wollowing method from a java interface:

Language: Java
Object process(Object request, String... parameter);

I did it in this way:

Language: Scala
def process(request: AnyRef, parameter: String*) : AnyRef = {
  ... //do something
}

But now I get the following error-message:

class SimpleCoRFilterProcessor needs to be abstract, since method process in trait FilterProcessor of 
 type (x$1: Any,x$2: [java.lang.String])java.lang.Object is not defined

to my mind AnyRef is the corresponding implementation to Object.

Any ideas what is the problem now?

Thanks, Barbara

Support the use of sourceinside tools to write code? (no replies)

2010-08-29T16:40:14+02:00

Support the use of sourceinside tools to write code?

Java Swing TableLayout (4 replies)

2010-08-29T10:26:17+02:00

Hallo,

ich habe gerade ein kleines Problem mit dem TableLayout für Swing.

Unter java habe ich das immer so gemacht (In einer Klasse, die von JFrame erbt):

double groesse[][] = {
{ TableLayout.FILL }, // Spalten
{ TableLayout.FILL,100} };// Reihen

TableLayout layout = new TableLayout(groesse);
setLayout(layout);

Ich programmiere unter Scala gerade an einem gleichen Dialog, es scheitert aber momentan an dieser Stelle. Wie würde das in Scala aussehen?
Ich habe es so gemacht:

object Hauptfenster extends JFrame{

this.setSize(new Dimension(600,400));
this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
setMinimumSize(new Dimension(200,200));
this.setVisible(true)

val groesse = new Array[Array[Double]](4,4)
groesse(0)(0) = 0.25
groesse(0)(1) = 0.25
groesse(0)(2) = 0.25
groesse(0)(3) = 0.25
groesse(1)(0) = 0.25
groesse(2)(0) = 0.25
groesse(3)(0) = 0.25

val layout = new TableLayout(groesse);
this.setLayout(layout);
}

Aber ich bekomme dann folgende Fehlermeldung:

error: overriding method layout in class Container of type ()Unit;
value layout needs `override' modifier
val layout = new TableLayout(groesse);

Ich verstehe nicht was ich falsch mache. Ist es das Array?

Ich würde mich über Anregungen freuen!

Error: The type scala.Nothing cannot be resolved (no replies)

2010-08-27T11:58:25+02:00

Hi,

I am getting below compilation errors if I use the scala-library-2.7.5. Actualy earlier we were using the Java 1.4 and scala-library-2.7.5-jvm4 so it was working fine. Now we are using the Java 1.5 and scala-library-2.7.5.

Error: The type scala.Nothing cannot be resolved. It is indirectly referenced from required .class files

private Map map = TreeHashMap$.MODULE$._empty();

Thanks
Mahesh

Reactions (3 replies)

2010-08-27T02:48:27+02:00

I dont get it. Why this code doesnt work?

listenTo(button1,button2)
reactions+= {
case ButtonClicked(button1)=>
println("sdf")
case ButtonClicked(button2)=>
println("sfg")

}

Eclipse shows such a message : unreachable code

Layout => null (2 replies)

2010-08-26T22:36:35+02:00

I have one short question about Layout. In Java we can use "null" Layout and set all positions for Components with help
of the method setBounds(); . Is it also possible i Scala. If yes could you write me how to do it?

On the end - Thank you very much!!!

Interpreter problems (no replies)

2010-08-23T23:54:03+02:00

Hi,
I'm using Scala to find the solution to some small math questions (e.g. what is the 763th five digit prime), and I noticed several problems with the 2.8 interpreter on Debian squeeze:
* "ctrl+left/right" doesn't jump to the next word
* "delete" deletes the left instead of the right character
* pasting a text containing tabs doesn't work, because it triggers the completion mode
* as soon as a line gets longer than the screen width, everything gets crazy. The cursor position has no relation to the edited text, moving the cursor changes the displayed text, typing a single character duplicates the whole line (on the screen)
* I can't figure out how to kill a endless loop. Ctrl+C only kills the whole interpreter with all interim results.

Does someone know a solution for these issues?

I tried to use the NetBeans Scala interpreter, and it doesn't have most of these problems, but it has others (e.g. no tab completion, very slow startup)

BeniBela

scala.swing layout constraints (no replies)

2010-08-23T21:25:27+02:00

How to set layout constraints for Swing components ?
For example enable maximum width for some components in BoxPanel, while set minimal widths for others.

Suche Interpreter für Programm (2 replies)

2010-08-22T23:43:04+02:00

Servus,

ich benötige eine Möglichkeit, mit der der Benutzer das vorhandene Programm dynamisch erweitern kann.
Folgendes sollte möglich sein
- ableiten von abstrakten Klassen
- funktionale Programmierung ala Scala (der Code ist in Scala geschrieben, daher habe ich nur Java 1.5 zur verfügung)
- (optinal) loop unrolling, inlining, ...

Gibt es hierfür etwas brauchbares?
Lässt sich der Scala-Interpreter in einem Programm nutzen?

Gruß,
Thomas

Netbeans Plugin slow (1 reply)

2010-08-20T15:46:48+02:00

Servus,

ich ärgere mich nun seit einiger Zeit mit dem Scala Netbeans Plugin rum.
Bei Dateien der Größe < 300 Zeilen funktioniert alles anstanslos. Aber wehe, die SourceDatei wird größer. Dann muss ich alle 1-3 Minuten Netbeans neu starten :-(

Folgendes tritt auf.
Schreibe ich in einer Datei mit ~500 Codezeilen, ist erstmal nichts ungewöhnliches festzustellen. Nach ein paar Zeilen bzw. 1-2 Minuten kommt der Editor plötzlich meiner Eingabe nicht mehr nach und die Auslastung eines Kernes der CPU steigt auf volle Last. Jetzt heißt es schnell speichern und Netbeans beenden. Da sonst Netbeans eine Minute später einfrirrt, sofern ich weiter in die Datei (Scala) schreibe.

Das ganze tritt nur bei Scala-Files auf!

Mein Betriebssystem ist Fedora x64, 16 GB Ram und 4 Kerne. Die Speicherbelastung von Netbeans beträgt 400 bis 450 MB.

Weiß jemand einen Rat, wie ich das Problem beseitigen könnte?
Evtl. über irgendwelche Parameter beim Start von Netbeans?

Gruß
Thomas

Suitable lexer and parser for Scala (1 reply)

2010-08-18T11:43:17+02:00

Hello,

there are a number of lexer and parser tools that produce Java output, for example JFlex and CUP. Are there similar tools that integrate well with Scala? I am mainly interested in LR (or some subclass of LR) parsers for educational purposes.

Best regards,
Boris

scala.Int in the Doc of Scala Standard Library 2.8.0 final (3 replies)

2010-08-17T10:37:28+02:00

Does anyone know why the specification of scala.Int does not appear in the doc of Scala Standard Library 2.8.0 final anymore. I can easily it in 2.7.7. But it seems that the new doc format filtered out the specifications of all value classes, which is a bit annoying.

Thanks

Operator overloading: Postfix and Infix (3 replies)

2010-08-15T11:00:45+02:00

Hello,

I write my own vector class (mathematic) and I would like write as

Language: Scala
val v = new Vector(1, 1, 1)
val s = 5.0
 
val res1 = v * s // no problem
val res2 = s * v // problem

How do I implement an infix + operator?

Language: Scala
def aMethod_= (a:Double) { new Vector( ... ) } // no problem
def *_= (a:Double) { new Vector ( .... ) } // Scala say: '=' expected but '_' found

'_' (underscore) vs 'null' in initialization? (4 replies)

2010-08-14T19:07:27+02:00

It seems like people try to avoid using the value 'null' in Scala, this might be a misperception though.

I have a class with an expensive no argument function call. I would like to change it from a def to a val (cache it) to improve performance like this:

Language: Scala
class A {  def f = ...  }  // change this
class A {  val f = ...  }  // to this

Unfortunately I can't because if it were evaluated on construction, it would become recursive. I would still like to cache the result for the performance gain, but I can't do it at construction time... An analogue to what I would do in Java would be something like this:

Language: Scala
class A {
  var cachedF = null
  def f = {
    if (cachedF == null){
      cachedF = ...
    }
    cachedF
  }
}

This uses the initial value 'null' of cachedF as a flag. I haven't seen initialization of var's to null in Scala though, people seem to use '_' instead (which I think is cool :) ) So maybe something like this is what I need:

Language: Scala
class A {
  var cachedF = _
  var fIsCached = false
  def f = {
    if (!fIsCached){
      fIsCached = true
      cachedF = ...
    }
    cachedF
  }
}

Any comments on which is better? I will probably use 'null' for now as it saves me a variable, but I would love to hear any arguments for alternatives.
-Ben

anyone using the intellij idea scala plugin? (5 replies)

2010-08-14T18:58:53+02:00

just curious. there's a free edition of idea supporting scala via a plugin that is according to some comment on scala-lang.org miles ahead of the eclipse plugin.
i never used the eclipse one, i can only say idea's is pretty stable

imperative code to a functional one (Project Euler problem code) (13 replies)

2010-08-13T17:33:20+02:00

Hello,

i rewrote Problem 11 ob Project Euler in Scala. I noticed that i'm not able to program a functional solution. I have four methods which do nearly the same. Do someone know a way to rewrite the calc-values with a more functional one?

Language: Scala
import collection.mutable.ArrayBuffer
import io.Source
 
object Problem11 {
	def main(args: Array[String]) {
		val ab = dataToArr()
 
		val calcHorizontal = {
			var greatest = 0
			for (i <- 0 until ab.length; j <- 0 until ab(i).length - 3) {
				val prod = ab(i)(j) * ab(i)(j + 1) * ab(i)(j + 2) * ab(i)(j + 3)
				if (prod > greatest) greatest = prod	  		
			}
			greatest
		}
 
		val calcVertical = {
			var greatest = 0
			for (i <- 0 until ab.length - 3; j <- 0 until ab(i).length) {
				val prod = ab(i)(j) * ab(i + 1)(j) * ab(i + 2)(j) * ab(i + 3)(j)
				if (prod > greatest) greatest = prod
			}
			greatest
		}
 
		val calcDiagForward = {
			var greatest = 0
			for (i <- 0 until ab.length - 3; j <- 0 until ab(i).length - 3) {
				val prod = ab(i)(j) * ab(i + 1)(j + 1) * ab(i + 2)(j + 2) * ab(i + 3)(j + 3)
				if (prod > greatest) greatest = prod
			}
			greatest
		}
 
		val calcDiagBackward = {
			var greatest = 0
			for (i <- 3 until ab.length; j <- 0 until ab(i).length - 3) {
				val prod = ab(i)(j) * ab(i - 1)(j + 1) * ab(i - 2)(j + 2) * ab(i - 3)(j + 3)
				if (prod > greatest) greatest = prod	  		
			}
			greatest
		}
 
		val greatest = List[Int](calcHorizontal, calcVertical, calcDiagForward, calcDiagBackward)
		printf("max:%d\n", greatest.max)
	}
 
	def dataToArr(): ArrayBuffer[ArrayBuffer[Int]] = {
		val arr = Source.fromFile("p11.txt").mkString.split("\n")
		val r = ArrayBuffer[ArrayBuffer[Int]]()
 
		for (i <- 0 until arr.length) {
			val row = arr(i).split(' ')
			val lb = ArrayBuffer[Int]()
			for (j <- 0 until row.length) lb += row(j).toInt
			r += lb
		}
		r
	}
}

unterschiedliche Interpretation (1 reply)

2010-08-11T22:57:17+02:00

Hallo,
ich bin gerade dabei ein wenig mit Scala herum zu probieren und dabei bin ich auf folgendes gestoßen:

Bei...

Language: Scala
val testList1 = List(1,2,3)
val testList2 = List(3,4,5)
val testList3 = testList1 ::: testList2
val testList4 = testList1.:::(testList2)
println(testList3 + " - " + testList4)

bekomme ich als Ausgabe:
List(1, 2, 3, 3, 4, 5) - List(3, 4, 5, 1, 2, 3)

und hier...

Language: Scala
val a = 6/2
val b = 6./(2)
println(a + " = " + b)

als Ausgabe:
3 = 3.0

Das verstehe ich nicht ganz. Kann mir das jemand erklären?

Danke,
Gruss Ray

List with traits... (4 replies)

2010-08-11T02:45:39+02:00

I was wanting to mix a trait into the List class, but it seems they are only constructable through the factory methods in the List object... Does anyone know how I might mix in a trait?
-Ben

No need to write setter? (4 replies)

2010-08-10T23:46:10+02:00

I've read there is no need to write getter and setter in scala, because one can start with

class A {
var x = 11
}

let the client change the value of x with
var m = new A
A.x = 22
A x = 14 //this also works!
A x 13 //doesn't work

Later one may decide to change x in class A by a setter - without breaking the client code!
class A {
private var x1 = 11 //need to change x's name otherwise we have a mismatch with method names
def x = x1 //GREAT
def x(i:Int) = { x1 = i }
}

client code:
var m = new A
A.x = 23 //doesn't work
A x = 13 //doesn't work

A x 13 //works, but breaks client code!

Is there any chance for writing a setter without breaking client code? As I understood it, this is one of the big promises which scala made...

Uniqueness issue (mini code review?)... (no replies)

2010-08-10T05:39:28+02:00

I've got a list of objects where some of the objects may be equal to each other... I want to pass this list to a function that will return a corresponding list of result values. My concern is that this function may use the objects as keys in a Map internally. There are random elements involved, so each object should have a different result value, even if some of the original objects are equal.

I came up with this way of handling the problem, and am wondering if it's "good", or if there are better, more standard ways of doing something like this. Say the objects in the list are of class A.

Language: Scala
class A(val hash: Int){
  override def hashCode = hash
 
  override def equals(other: Any): Boolean = other match{
    case that: A => hash == that.hash
    case _ => false
  }
}
 
trait Id{
  val id: Int
 
  override def hashCode =
    super.hashCode * 41 + id
 
  override def equals(other: Any) = other match {
    case that: Id => (this.id == that.id) && super.equals(that)
    case _ => false
  }
}
 
// instead of normal construction for class A  I can use:
val a = new A(10) with Id {val id = 1}
val b = new A(10) with Id {val id = 2}

In my situation the function is expecting the objects to be instances of A, and I have control over the construction of the objects. I thought of trying to wrap them with an id, but I would have to subclass A and delegate all the methods to the wrapped instance... I was looking for something better. The above is better I think, is there something better yet?
-Ben

trouble with scala.tools.nsc.Interpreter.scala (3 replies)

2010-08-09T19:59:02+02:00

one of the recent (since May) changes has caused boundNames to include defined functions as well as defined values. Since this seems to make sense, I'm wondering how can I figure out now which name is what exactly?

Welcome to Scala version 2.8.0.final (Java HotSpot(TM) Server VM, Java 1.6.0_20).
Type in expressions to have them evaluated.
Type :help for more information.

scala> val repl = new scala.tools.nsc.Interpreter()
repl: scala.tools.nsc.Interpreter = scala.tools.nsc.Interpreter@1579371

scala> repl.interpret("def f(x: Int) = x*x")
f: (x: Int)Int
res0: scala.tools.nsc.InterpreterResults.Result = Success

following this, the repl.prevRequests.last.boundNames map (_.decode) will contain the name "f".

when then trying to extract its value...boom...big bada boom:

scala> repl.evalExpr[Any] ("f")
:6: error: missing arguments for method f in object $iw;
follow this method with `_' if you want to treat it as a partially applied function
val synthvar$0 = { f }
^
:6: error: not found: value synthvar$0
synthvar$0
^
scala.tools.nsc.Interpreter$InterpreterEvalException: Eval error.
at scala.tools.nsc.Interpreter.evalError(Interpreter.scala:1131)
at scala.tools.nsc.Interpreter.evalExpr(Interpreter.scala:1156)
at .(:7)
at .()
at RequestResult$.(:9)
at RequestResult$.()
at RequestResult$scala_repl_result()
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:597)
at scala.tools.nsc.Interpreter$Request$$anonfun$loadAndRun$1$$anonfun$apply$18.apply(Interpreter.scala:981)
at scala.tools.nsc.Interpr...

def update (3 replies)

2010-08-07T21:47:09+02:00

Hello,

it is possible to def a update method as follows?

Language: Scala
class A {
  var s:Array[Array[String]]
 // init. s
  def apply(i:Int)(j:Int) = s(i)(j)
 
  def update ???
}
 
val a = new A
 
a(0)(0) = "hello"
 
Console.println(a(0)(0)

I don't get it... (4 replies)

2010-08-07T18:28:10+02:00

I just looked at all the Kestral code and it's basically just mutable state w/syncronized blocks everywhere - and it may just as well be Java.
In so far as Scala is a "better java" I can agree - but I'm not seeing features in Scala that I'd see in Haskell or even F# (or Ruby,or others) that would lead me to a "paradigm shift" in programming style vis-a-vis Java - and if that's not going to happen, then why not stick with code that is maintainable by more programmers? Would I rather program in Scala than Java? - sure - but in employing a second language, it seems like one would want to choose a different style of language that solved problems differently. Or do people like Scala exactly becasue it's so familiar, compared to let's say Clojure which also targets JVM but is lispy.) Thanks!