summaryrefslogtreecommitdiffhomepage
path: root/chapel.html.markdown
blob: 02a96b04671a14b581186c31a25aa3053706f607 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
955
956
957
958
959
960
961
962
963
964
965
966
967
968
969
970
971
972
973
974
975
976
977
978
979
980
981
982
983
984
985
986
987
988
989
990
991
992
993
994
995
996
997
998
999
1000
1001
1002
1003
1004
1005
1006
1007
1008
1009
1010
1011
1012
1013
1014
1015
1016
1017
1018
1019
1020
1021
1022
1023
1024
1025
1026
1027
1028
1029
1030
1031
1032
1033
1034
1035
1036
1037
1038
1039
1040
1041
1042
1043
1044
1045
1046
1047
1048
1049
1050
1051
1052
1053
1054
1055
1056
1057
1058
1059
1060
1061
1062
1063
1064
1065
1066
1067
1068
1069
1070
1071
1072
1073
1074
1075
1076
1077
1078
1079
1080
1081
1082
1083
1084
1085
1086
1087
1088
1089
1090
1091
1092
1093
1094
1095
1096
1097
1098
1099
1100
1101
1102
1103
---
language: chapel
filename: learnchapel.chpl
contributors:
    - ["Ian J. Bertolacci", "http://www.cs.colostate.edu/~ibertola/"]
---

You can read all about Chapel at [Cray's official Chapel website](http://chapel.cray.com).
In short, Chapel is an open-source, high-productivity, parallel-programming language in development at Cray Inc., and is designed to run on multi-core PCs as well as multi-kilocore supercomputers.

More information and support can be found at the bottom of this document.

```c
// Comments are C-family style
// one line comment
/*
  multi-line comment
*/

// Basic printing
write( "Hello, " );
writeln( "World!" );
// write and writeln can take a list of things to print.
// each thing is printed right next to each other, so include your spacing!
writeln( "There are ", 3, " commas (\",\") in this line of code" );
// Different output channels
stdout.writeln( "This goes to standard output, just like plain writeln() does");
stderr.writeln( "This goes to standard error" );

// Variables don't have to be explicitly typed as long as
// the compiler can figure out the type that it will hold.
var myVar = 10; // 10 is an int, so myVar is implicitly an int
myVar = -10;
var mySecondVar = myVar;
// var anError; // this would be a compile-time error.

// We can (and should) explicitly type things
var myThirdVar: real;
var myFourthVar: real = -1.234;
myThirdVar = myFourthVar;

// There are a number of basic types.
var myInt: int = -1000; // Signed ints
var myUint: uint = 1234; // Unsigned ints
var myReal: real = 9.876; // Floating point numbers
var myImag: imag = 5.0i; // Imaginary numbers
var myCplx: complex = 10 + 9i; // Complex numbers
myCplx = myInt + myImag ; // Another way to form complex numbers
var myBool: bool = false; // Booleans
var myStr: string = "Some string..."; // Strings

// Some types can have sizes
var my8Int: int(8) = 10; // 8 bit (one byte) sized int;
var my64Real: real(64) = 1.516; // 64 bit (8 bytes) sized real

// Typecasting
var intFromReal = myReal : int;
var intFromReal2: int = myReal : int;

// consts are constants, they cannot be changed after set in runtime.
const almostPi: real = 22.0/7.0;

// params are constants whose value must be known statically at compile-time
// Their value cannot be changed.
param compileTimeConst: int = 16;

// The config modifier allows values to be set at the command line
// and is much easier than the usual getOpts debacle
// config vars and consts can be changed through the command line at run time
config var varCmdLineArg: int = -123;
config const constCmdLineArg: int = 777;
// Set with --VarName=Value or --VarName Value at run time

// config params can be set/changed at compile-time
config param paramCmdLineArg: bool = false;
// Set config with --set paramCmdLineArg=value at compile-time
writeln( varCmdLineArg, ", ", constCmdLineArg, ", ", paramCmdLineArg );

// refs operate much like a reference in C++
var actual = 10;
ref refToActual = actual; // refToActual refers to actual
writeln( actual, " == ", refToActual ); // prints the same value
actual = -123; // modify actual (which refToActual refers to)
writeln( actual, " == ", refToActual ); // prints the same value
refToActual = 99999999; // modify what refToActual refers to (which is actual)
writeln( actual, " == ", refToActual ); // prints the same value

// Math operators
var a: int, thisInt = 1234, thatInt = 5678;
a = thisInt + thatInt;  // Addition
a = thisInt * thatInt;  // Multiplication
a = thisInt - thatInt;  // Subtraction
a = thisInt / thatInt;  // Division
a = thisInt ** thatInt; // Exponentiation
a = thisInt % thatInt;  // Remainder (modulo)

// Logical Operators
var b: bool, thisBool = false, thatBool = true;
b = thisBool && thatBool; // Logical and
b = thisBool || thatBool; // Logical or
b = !thisBool;            // Logical negation

// Relational Operators
b = thisInt > thatInt;           // Greater-than
b = thisInt >= thatInt;          // Greater-than-or-equal-to
b = thisInt < a && a <= thatInt; // Less-than, and, less-than-or-equal-to
b = thisInt != thatInt;          // Not-equal-to
b = thisInt == thatInt;          // Equal-to

// Bitwise operations
a = thisInt << 10;     // Left-bit-shift by 10 bits;
a = thatInt >> 5;      // Right-bit-shift by 5 bits;
a = ~thisInt;          // Bitwise-negation
a = thisInt ^ thatInt; // Bitwise exclusive-or

// Compound assignment operations
a += thisInt;          // Addition-equals ( a = a + thisInt;)
a *= thatInt;          // Times-equals ( a = a * thatInt; )
b &&= thatBool;        // Logical-and-equals ( b = b && thatBool; )
a <<= 3;               // Left-bit-shift-equals ( a = a << 10; )
// and many, many more.
// Unlike other C family languages there are no
// pre/post-increment/decrement operators like
//  ++j, --j, j++, j--

// Swap operator
var old_this = thisInt;
var old_that = thatInt;
thisInt <=> thatInt; // Swap the values of thisInt and thatInt
writeln( (old_this == thatInt) && (old_that == thisInt) );

// Operator overloads can also be defined, as we'll see with procedures

// Tuples can be of the same type
var sameTup: 2*int = (10,-1);
var sameTup2 = (11, -6);
// or different types
var diffTup: (int,real,complex) = (5, 1.928, myCplx);
var diffTupe2 = ( 7, 5.64, 6.0+1.5i );

// Accessed using array bracket notation
// However, tuples are all 1-indexed
writeln( "(", sameTup[1], ",", sameTup[2], ")" );
writeln( diffTup );

// Tuples can also be written into.
diffTup[1] = -1;

// Can expand tuple values into their own variables
var (tupInt, tupReal, tupCplx) = diffTup;
writeln( diffTup == (tupInt, tupReal, tupCplx) );

// Useful for writing a list of variables ( as is common in debugging)
writeln( (a,b,thisInt,thatInt,thisBool,thatBool) );

// Type aliasing
type chroma = int;        // Type of a single hue
type RGBColor = 3*chroma; // Type representing a full color
var black: RGBColor = ( 0,0,0 );
var white: RGBColor = ( 255, 255, 255 );

// If-then-else works just like any other C-family language
if 10 < 100 then
  writeln( "All is well" );

if -1 < 1 then
  writeln( "Continuing to believe reality" );
else
  writeln( "Send mathematician, something's wrong" );

if ( 10 > 100 ) {
  writeln( "Universe broken. Please reboot universe." );
}

if ( a % 2 == 0 ) {
  writeln( a, " is even." );
} else {
  writeln( a, " is odd." );
}

if ( a % 3 == 0 ) {
  writeln( a, " is even divisible by 3." );
} else if ( a % 3 == 1 ){
  writeln( a, " is divided by 3 with a remainder of 1." );
} else {
  writeln( b, " is divided by 3 with a remainder of 2." );
}

// Ternary: if-then-else in a statement
var maximum = if ( thisInt < thatInt ) then thatInt else thisInt;

// Select statements are much like switch statements in other languages
// However, Select statements don't cascade like in C or Java
var inputOption = "anOption";
select( inputOption ){
  when "anOption" do writeln( "Chose 'anOption'" );
  when "otherOption" {
    writeln( "Chose 'otherOption'" );
    writeln( "Which has a body" );
  }
  otherwise {
    writeln( "Any other Input" );
    writeln( "the otherwise case doesn't need a do if the body is one line" );
  }
}

// While and Do-While loops are basically the same in every language.
var j: int = 1;
var jSum: int = 0;
while( j <= 1000 ){
  jSum += j;
  j += 1;
}
writeln( jSum );

// Do-While loop
do{
  jSum += j;
  j += 1;
}while( j <= 10000 );
writeln( jSum );

// For loops are much like those in python in that they iterate over a range.
// Ranges themselves are types, and can be stuffed into variables
// (more about that later)
for i in 1..10 do write( i , ", ") ;
writeln( );

var iSum: int = 0;
for i in 1..1000 {
  iSum += i;
}
writeln( iSum );

for x in 1..10 {
  for y in 1..10 {
    write( (x,y), "\t" );
  }
  writeln( );
}

// Ranges and Domains
// For-loops and arrays both use ranges and domains to
// define an index set that can be iterated over.
// Ranges are single dimensional
// Domains can be multi-dimensional and can
// represent indices of different types as well.
// They are first-class citizen types, and can be assigned into variables
var range1to10: range = 1..10;  // 1, 2, 3, ..., 10
var range2to11 = 2..11; // 2, 3, 4, ..., 11
var rangeThistoThat: range = thisInt..thatInt; // using variables
var rangeEmpty: range = 100..-100 ; // this is valid but contains no indices

// Ranges can be unbounded
var range1toInf: range(boundedType=BoundedRangeType.boundedLow) = 1.. ;
// 1, 2, 3, 4, 5, ...
// Note: the range(boundedType= ... ) is only
// necessary if we explicitly type the variable

var rangeNegInfto1 = ..1; // ..., -4, -3, -2, -1, 0, 1

// Ranges can be strided using the 'by' operator.
var range2to10by2: range(stridable=true) = 2..10 by 2; // 2, 4, 6, 8, 10
// Note: the range(stridable=true) is only
// necessary if we explicitly type the variable

// Use by to create a reverse range
var reverse2to10by2 = 10..2 by -2; // 10, 8, 6, 4, 2

// The end point of a range can be determined using the count (#) operator
var rangeCount: range = -5..#12; // range from -5 to 6

// Can mix operators
var rangeCountBy: range(stridable=true) = -5..#12 by 2; // -5, -3, -1, 1, 3, 5
writeln( rangeCountBy );

// Can query properties of the range
// Print the first index, last index, number of indices,
// stride, and ask if 2 is include in the range
writeln( ( rangeCountBy.first, rangeCountBy.last, rangeCountBy.length,
           rangeCountBy.stride, rangeCountBy.member( 2 ) ) );

for i in rangeCountBy{
  write( i, if i == rangeCountBy.last then "\n" else ", " );
}

// Rectangular domains are defined using the same range syntax
// However they are required to be bounded (unlike ranges)
var domain1to10: domain(1) = {1..10};        // 1D domain from 1..10;
var twoDimensions: domain(2) = {-2..2,0..2}; // 2D domain over product of ranges
var thirdDim: range = 1..16;
var threeDims: domain(3) = {thirdDim, 1..10, 5..10}; // using a range variable

// Can iterate over the indices as tuples
for idx in twoDimensions do
  write( idx , ", ");
writeln( );

// or can deconstruct the tuple
for (x,y) in twoDimensions {
  write( "(", x, ", ", y, ")", ", " );
}
writeln( );

// Associative domains act like sets
var stringSet: domain(string); // empty set of strings
stringSet += "a";
stringSet += "b";
stringSet += "c";
stringSet += "a"; // Redundant add "a"  
stringSet -= "c"; // Remove "c"
writeln( stringSet );

// Both ranges and domains can be sliced to produce a range or domain with the
// intersection of indices
var rangeA = 1.. ; // range from 1 to infinity
var rangeB =  ..5; // range from negative infinity to 5
var rangeC = rangeA[rangeB]; // resulting range is 1..5
writeln( (rangeA, rangeB, rangeC ) );

var domainA = {1..10, 5..20};
var domainB = {-5..5, 1..10};
var domainC = domainA[domainB];
writeln( (domainA, domainB, domainC) );

// Array are similar to those of other languages.
// Their sizes are defined using domains that represent their indices
var intArray: [1..10] int;
var intArray2: [{1..10}] int; //equivalent

// Accessed using bracket notation
for i in 1..10 do
  intArray[i] = -i;
writeln( intArray );
// We cannot access intArray[0] because it exists outside
// of the index set, {1..10}, we defined it to have.
// intArray[11] is illegal for the same reason.

var realDomain: domain(2) = {1..5,1..7};
var realArray: [realDomain] real;
var realArray2: [1..5,1..7] real;   // Equivalent
var realArray3: [{1..5,1..7}] real; // Equivalent

for i in 1..5 {
  for j in realDomain.dim(2) {   // Only use the 2nd dimension of the domain
    realArray[i,j] = -1.61803 * i + 0.5 * j;  // Access using index list
    var idx: 2*int = (i,j);                   // Note: 'index' is a keyword
    realArray[idx] = - realArray[(i,j)];      // Index using tuples
  }
}

// Arrays have domains as members that we can iterate over
for idx in realArray.domain {  // Again, idx is a 2*int tuple
  realArray[idx] = 1 / realArray[idx[1],idx[2]]; // Access by tuple and list
}

writeln( realArray );

// Can also iterate over the values of an array
var rSum: real = 0;
for value in realArray {
  rSum += value; // Read a value
  value = rSum;  // Write a value
}
writeln( rSum, "\n", realArray );

// Using associative domains we can create associative arrays (dictionaries)
var dictDomain: domain(string) = { "one", "two" };
var dict: [dictDomain] int = [ "one" => 1, "two" => 2 ];
dict["three"] = 3;
for key in dictDomain do writeln( dict[key] );

// Arrays can be assigned to each other in different ways
var thisArray : [{0..5}] int = [0,1,2,3,4,5];
var thatArray : [{0..5}] int;

// Simply assign one to the other.
// This copies thisArray into thatArray, instead of just creating a reference.
// Modifying thisArray does not also modify thatArray.
thatArray = thisArray;
thatArray[1] = -1;
writeln( (thisArray, thatArray) );

// Assign a slice one array to a slice (of the same size) of the other.
thatArray[{4..5}] = thisArray[{1..2}];
writeln( (thisArray, thatArray) );

// Operation can also be promoted to work on arrays.
var thisPlusThat = thisArray + thatArray;
writeln( thisPlusThat );

// Arrays and loops can also be expressions, where loop
// body's expression is the result of each iteration.
var arrayFromLoop = for i in 1..10 do i;
writeln( arrayFromLoop );

// An expression can result in nothing,
// such as when filtering with an if-expression
var evensOrFives = for i in 1..10 do if (i % 2 == 0 || i % 5 == 0) then i;

writeln( arrayFromLoop );

// Or could be written with a bracket notation
// Note: this syntax uses the 'forall' parallel concept discussed later.
var evensOrFivesAgain = [ i in 1..10 ] if (i % 2 == 0 || i % 5 == 0) then i;

// Or over the values of the array
arrayFromLoop = [ value in arrayFromLoop ] value + 1;

// Note: this notation can get somewhat tricky. For example:
// evensOrFives = [ i in 1..10 ] if (i % 2 == 0 || i % 5 == 0) then i;
// would break.
// The reasons for this are explained in depth when discussing zipped iterators.

// Chapel procedures have similar syntax to other languages functions.
proc fibonacci( n : int ) : int {
  if ( n <= 1 ) then return n;
  return fibonacci( n-1 ) + fibonacci( n-2 );
}

// Input parameters can be untyped (a generic procedure)
proc doublePrint( thing ): void {
  write( thing, " ", thing, "\n");
}

// Return type can be inferred (as long as the compiler can figure it out)
proc addThree( n ) {
  return n + 3;
}

doublePrint( addThree( fibonacci( 20 ) ) );

// Can also take 'unlimited' number of parameters
proc maxOf( x ...?k ) {
  // x refers to a tuple of one type, with k elements
  var maximum = x[1];
  for i in 2..k do maximum = if (maximum < x[i]) then x[i] else maximum;
  return maximum;
}
writeln( maxOf( 1, -10, 189, -9071982, 5, 17, 20001, 42 ) );

// The ? operator is called the query operator, and is used to take
// undetermined values (like tuple or array sizes, and generic types).

// Taking arrays as parameters.
// The query operator is used to determine the domain of A.
// This is important to define the return type (if you wanted to)
proc invertArray( A: [?D] int ): [D] int{
  for a in A do a = -a;
  return A;
}

writeln( invertArray( intArray ) );

// Procedures can have default parameter values, and
// the parameters can be named in the call, even out of order
proc defaultsProc( x: int, y: real = 1.2634 ): (int,real){
  return (x,y);
}

writeln( defaultsProc( 10 ) );
writeln( defaultsProc( x=11 ) );
writeln( defaultsProc( x=12, y=5.432 ) );
writeln( defaultsProc( y=9.876, x=13 ) );

// Intent modifiers on the arguments convey how
// those arguments are passed to the procedure
// in: copy arg in, but not out
// out: copy arg out, but not in
// inout: copy arg in, copy arg out
// ref: pass arg by reference
proc intentsProc( in inarg, out outarg, inout inoutarg, ref refarg ){
  writeln( "Inside Before: ", (inarg, outarg, inoutarg, refarg) );
  inarg = inarg + 100;
  outarg = outarg + 100;
  inoutarg = inoutarg + 100;
  refarg = refarg + 100;
  writeln( "Inside After: ", (inarg, outarg, inoutarg, refarg) );
}

var inVar: int = 1;
var outVar: int = 2;
var inoutVar: int = 3;
var refVar: int = 4;
writeln( "Outside Before: ", (inVar, outVar, inoutVar, refVar) );
intentsProc( inVar, outVar, inoutVar, refVar );
writeln( "Outside After: ", (inVar, outVar, inoutVar, refVar) );

// Similarly we can define intents on the return type
// refElement returns a reference to an element of array
proc refElement( array : [?D] ?T, idx ) ref : T {
  return array[ idx ]; // returns a reference to
}

var myChangingArray : [1..5] int = [1,2,3,4,5];
writeln( myChangingArray );
// Store reference to element in ref variable
ref refToElem = refElement( myChangingArray, 5 );
writeln( refToElem );
refToElem = -2; // modify reference which modifies actual value in array
writeln( refToElem );
writeln( myChangingArray );
// This makes more practical sense for class methods where references to
// elements in a data-structure are returned via a method or iterator

// We can query the type of arguments to generic procedures
// Here we define a procedure that takes two arguments of
// the same type, yet we don't define what that type is.
proc genericProc( arg1 : ?valueType, arg2 : valueType ): void {
  select( valueType ){
    when int do writeln( arg1, " and ", arg2, " are ints" );
    when real do writeln( arg1, " and ", arg2, " are reals" );
    otherwise writeln( arg1, " and ", arg2, " are somethings!" );
  }
}

genericProc( 1, 2 );
genericProc( 1.2, 2.3 );
genericProc( 1.0+2.0i, 3.0+4.0i );

// We can also enforce a form of polymorphism with the 'where' clause
// This allows the compiler to decide which function to use.
// Note: that means that all information needs to be known at compile-time.
// The param modifier on the arg is used to enforce this constraint.
proc whereProc( param N : int ): void
 where ( N > 0 ) {
  writeln( "N is greater than 0" );  
}

proc whereProc( param N : int ): void
 where ( N < 0 ) {
  writeln( "N is less than 0" );  
}

whereProc( 10 );
whereProc( -1 );
// whereProc( 0 ) would result in a compiler error because there
// are no functions that satisfy the where clause's condition.
// We could have defined a whereProc without a where clause that would then have
// served as a catch all for all the other cases (of which there is only one).

// Operator definitions are through procedures as well.
// We can define the unary operators:
// + - ! ~
// and the binary operators:
// + - * / % ** == <= >= < > << >> & | ˆ by
// += -= *= /= %= **= &= |= ˆ= <<= >>= <=>

// Boolean exclusive or operator
proc ^( left : bool, right : bool ): bool {
  return (left || right) && !( left && right );
}

writeln( true  ^ true  );
writeln( false ^ true  );
writeln( true  ^ false );
writeln( false ^ false );

// Define a * operator on any two types that returns a tuple of those types
proc *( left : ?ltype, right : ?rtype): ( ltype, rtype ){
  return (left, right );
}

writeln( 1 * "a" ); // Uses our * operator
writeln( 1 * 2 );   // Uses the default * operator

/*
Note: You could break everything if you get careless with your overloads.
This here will break everything. Don't do it.
proc +( left: int, right: int ): int{
  return left - right;
}
*/

// Iterators are a sisters to the procedure, and almost
// everything about procedures also applies to iterators
// However, instead of returning a single value,
// iterators yield many values to a loop.
// This is useful when a complicated set or order of iterations is needed but
// allows the code defining the iterations to be separate from the loop body.
iter oddsThenEvens( N: int ): int {
  for i in 1..N by 2 do
    yield i; // yield values instead of returning.
  for i in 2..N by 2 do
    yield i;
}

for i in oddsThenEvens( 10 ) do write( i, ", " );
writeln( );

// Iterators can also yield conditionally, the result of which can be nothing
iter absolutelyNothing( N ): int {
  for i in 1..N {
    if ( N < i ) { // Always false
      yield i;     // Yield statement never happens
    }
  }
}

for i in absolutelyNothing( 10 ){
  writeln( "Woa there! absolutelyNothing yielded ", i );
}

// We can zipper together two or more iterators (who have the same number
// of iterations)  using zip() to create a single zipped iterator, where each
// iteration of the zipped iterator yields a tuple of one value yielded
// from each iterator.
                                 // Ranges have implicit iterators
for (positive, negative) in zip( 1..5, -5..-1) do
  writeln( (positive, negative) );

// Zipper iteration is quite important in the assignment of arrays,
// slices of arrays, and array/loop expressions.
var fromThatArray : [1..#5] int = [1,2,3,4,5];
var toThisArray : [100..#5] int;

// The operation
toThisArray = fromThatArray;
// is produced through
for (i,j) in zip( toThisArray.domain, fromThatArray.domain) {
  toThisArray[ i ] = fromThatArray[ j ];
}

toThisArray = [ j in -100..#5 ] j;
writeln( toThisArray );
// is produced through
for (i, j) in zip( toThisArray.domain, -100..#5 ){
  toThisArray[i] = j;
}
writeln( toThisArray );

// This is all very important in undestanding why the statement
// var iterArray : [1..10] int = [ i in 1..10 ] if ( i % 2 == 1 ) then j;
// exhibits a runtime error.
// Even though the domain of the array and the loop-expression are
// the same size, the body of the expression can be though of as an iterator.
// Because iterators can yield nothing, that iterator yields a different number
// of things than the domain of the array or loop, which is not allowed.

// Classes are similar to those in C++ and Java.
// They currently lack privatization
class MyClass {
  // Member variables
  var memberInt : int;
  var memberBool : bool = true;

  // Classes have default constructors that don't need to be coded (see below)
  // Our explicitly defined constructor
  proc MyClass( val : real ){
    this.memberInt = ceil( val ): int;
  }

  // Our explicitly defined destructor
  proc ~MyClass( ){
    writeln( "MyClass Destructor called ", (this.memberInt, this.memberBool) );
  }

  // Class methods
  proc setMemberInt( val: int ){
    this.memberInt = val;
  }

  proc setMemberBool( val: bool ){
    this.memberBool = val;
  }

  proc getMemberInt( ): int{
    return this.memberInt;
  }

  proc getMemberBool( ): bool {
    return this.memberBool;
  }

}

// Construct using default constructor, using default values
var myObject = new MyClass( 10 );
    myObject = new MyClass( memberInt = 10 ); // Equivalent
writeln( myObject.getMemberInt( ) );
// ... using our values
var myDiffObject = new MyClass( -1, true );
    myDiffObject = new MyClass( memberInt = -1,
                                memberBool = true ); // Equivalent
writeln( myDiffObject );

// Construct using written constructor
var myOtherObject = new MyClass( 1.95 );
    myOtherObject = new MyClass( val = 1.95 ); // Equivalent
writeln( myOtherObject.getMemberInt( ) );

// We can define an operator on our class as well but
// the definition has to be outside the class definition
proc +( A : MyClass, B : MyClass) : MyClass {
  return new MyClass( memberInt = A.getMemberInt( ) + B.getMemberInt( ),
                      memberBool = A.getMemberBool( ) || B.getMemberBool( ) );
}

var plusObject = myObject + myDiffObject;
writeln( plusObject );

// Destruction
delete myObject;
delete myDiffObject;
delete myOtherObject;
delete plusObject;

// Classes can inherit from one or more parent classes
class MyChildClass : MyClass {
  var memberComplex: complex;
}

// Generic Classes
class GenericClass {
  type classType;
  var classDomain: domain(1);
  var classArray: [classDomain] classType;

  // Explicit constructor
  proc GenericClass( type classType, elements : int ){
    this.classDomain = {1..#elements};
  }

  // Copy constructor
  // Note: We still have to put the type as an argument, but we can
  // default to the type of the other object using the query (?) operator
  // Further, we can take advantage of this to allow our copy constructor
  // to copy classes of different types and cast on the fly
  proc GenericClass( other : GenericClass(?otherType),
                     type classType = otherType ) {
    this.classDomain = other.classDomain;
    // Copy and cast
    for idx in this.classDomain do this[ idx ] = other[ idx ] : classType;
  }

  // Define bracket notation on a GenericClass
  // object so it can behave like a normal array
  // i.e. objVar[ i ] or objVar( i )
  proc this( i : int ) ref : classType {
    return this.classArray[ i ];
  }

  // Define an implicit iterator for the class
  // to yield values from the array to a loop
  // i.e. for i in objVar do ....
  iter these( ) ref : classType {
    for i in this.classDomain do
      yield this[i];
  }

}

var realList = new GenericClass( real, 10 );
// We can assign to the member array of the object using the bracket
// notation that we defined ( proc this( i: int ){ ... }  )
for i in realList.classDomain do realList[i] = i + 1.0;
// We can iterate over the values in our list with the iterator
// we defined ( iter these( ){ ... } )
for value in realList do write( value, ", " );
writeln( );

// Make a copy of realList using the copy constructor
var copyList = new GenericClass( realList );
for value in copyList do write( value, ", " );
writeln( );

// Make a copy of realList and change the type, also using the copy constructor
var copyNewTypeList = new GenericClass( realList, int );
for value in copyNewTypeList do write( value, ", " );
writeln( );

// Modules are Chapel's way of managing name spaces.
// The files containing these modules do not need to be named after the modules
// (as in Java), but files implicitly name modules.
// In this case, this file implicitly names the 'learnchapel' module

module OurModule {
  // We can use modules inside of other modules.
  use Time; // Time is one of the standard modules.

  // We'll use this procedure in the parallelism section.
  proc countdown( seconds: int ){
    for i in 1..seconds by -1 {
      writeln( i );
      sleep( 1 );
    }
  }

  // Submodules of OurModule
  // It is possible to create arbitrarily deep module nests.
  module ChildModule {
    proc foo(){
      writeln( "ChildModule.foo()");
    }
  }

  module SiblingModule {
    proc foo(){
      writeln( "SiblingModule.foo()" );
    }
  }
} // end OurModule

// Using OurModule also uses all the modules it uses.
// Since OurModule uses Time, we also use time.
use OurModule;

// At this point we have not used ChildModule or SiblingModule so their symbols
// (i.e. foo ) are not available to us.
// However, the module names are, and we can explicitly call foo() through them.
SiblingModule.foo();         // Calls SiblingModule.foo()

// Super explicit naming.
OurModule.ChildModule.foo(); // Calls ChildModule.foo()

use ChildModule;
foo();   // Less explicit call on ChildModule.foo()

// We can declare a main procedure
// Note: all the code above main still gets executed.
proc main(){

  // Parallelism
  // In other languages, parallelism is typically done with
  // complicated libraries and strange class structure hierarchies.
  // Chapel has it baked right into the language.

  // A begin statement will spin the body of that statement off
  // into one new task.
  // A sync statement will ensure that the progress of the main
  // task will not progress until the children have synced back up.
  sync {
    begin { // Start of new task's body
      var a = 0;
      for i in 1..1000 do a += 1;
      writeln( "Done: ", a);
    } // End of new tasks body
    writeln( "spun off a task!");
  }
  writeln( "Back together" );

  proc printFibb( n: int ){
    writeln( "fibonacci(",n,") = ", fibonacci( n ) );
  }

  // A cobegin statement will spin each statement of the body into one new task
  cobegin {
    printFibb( 20 ); // new task
    printFibb( 10 ); // new task
    printFibb( 5 );  // new task
    {
      // This is a nested statement body and thus is a single statement
      // to the parent statement and is executed by a single task
      writeln( "this gets" );
      writeln( "executed as" );
      writeln( "a whole" );
    }
  }
  // Notice here that the prints from each statement may happen in any order.

  // Coforall loop will create a new task for EACH iteration
  var num_tasks = 10; // Number of tasks we want
  coforall taskID in 1..#num_tasks {
    writeln( "Hello from task# ", taskID );
  }
  // Again we see that prints happen in any order.
  // NOTE! coforall should be used only for creating tasks!
  // Using it to iterating over a structure is very a bad idea!

  // forall loops are another parallel loop, but only create a smaller number
  // of tasks, specifically --dataParTasksPerLocale=number of task
  forall i in 1..100 {
    write( i, ", ");
  }
  writeln( );
  // Here we see that there are sections that are in order, followed by
  // a section that would not follow ( e.g. 1, 2, 3, 7, 8, 9, 4, 5, 6, ).
  // This is because each task is taking on a chunk of the range 1..10
  // (1..3, 4..6, or 7..9) doing that chunk serially, but each task happens
  // in parallel.
  // Your results may depend on your machine and configuration

  // For both the forall and coforall loops, the execution of the
  // parent task will not continue until all the children sync up.

  // forall loops are particularly useful for parallel iteration over arrays.
  // Lets run an experiment to see how much faster a parallel loop is
  use Time; // Import the Time module to use Timer objects
  var timer: Timer;
  var myBigArray: [{1..4000,1..4000}] real; // Large array we will write into

  // Serial Experiment
  timer.start( ); // Start timer
  for (x,y) in myBigArray.domain { // Serial iteration
    myBigArray[x,y] = (x:real) / (y:real);
  }
  timer.stop( ); // Stop timer
  writeln( "Serial: ", timer.elapsed( ) ); // Print elapsed time
  timer.clear( ); // Clear timer for parallel loop

  // Parallel Experiment
  timer.start( ); // start timer
  forall (x,y) in myBigArray.domain { // Parallel iteration
    myBigArray[x,y] = (x:real) / (y:real);
  }
  timer.stop( ); // Stop timer
  writeln( "Parallel: ", timer.elapsed( ) ); // Print elapsed time
  timer.clear( );
  // You may have noticed that (depending on how many cores you have)
  // that the parallel loop went faster than the serial loop

  // The bracket style loop-expression described
  // much earlier implicitly uses a forall loop.
  [ val in myBigArray ] val = 1 / val; // Parallel operation

  // Atomic variables, common to many languages, are ones whose operations
  // occur uninterupted. Multiple threads can both modify atomic variables
  // and can know that their values are safe.
  // Chapel atomic variables can be of type bool, int, uint, and real.
  var uranium: atomic int;
  uranium.write( 238 );      // atomically write a variable
  writeln( uranium.read() ); // atomically read a variable

  // operations are described as functions, you could define your own operators.
  uranium.sub( 3 ); // atomically subtract a variable
  writeln( uranium.read() );

  var replaceWith = 239;
  var was = uranium.exchange( replaceWith );
  writeln( "uranium was ", was, " but is now ", replaceWith );

  var isEqualTo = 235;
  if ( uranium.compareExchange( isEqualTo, replaceWith ) ) {
    writeln( "uranium was equal to ", isEqualTo,
             " so replaced value with ", replaceWith );
  } else {
    writeln( "uranium was not equal to ", isEqualTo,
             " so value stays the same...  whatever it was" );
  }

  sync {
    begin { // Reader task
      writeln( "Reader: waiting for uranium to be ", isEqualTo );
      uranium.waitFor( isEqualTo );
      writeln( "Reader: uranium was set (by someone) to ", isEqualTo );
    }

    begin { // Writer task
      writeln( "Writer: will set uranium to the value ", isEqualTo, " in..." );
      countdown( 3 );
      uranium.write( isEqualTo );
    }
  }

  // sync vars have two states: empty and full.
  // If you read an empty variable or write a full variable, you are waited
  // until the variable is full or empty again
  var someSyncVar$: sync int; // varName$ is a convention not a law.
  sync {
    begin { // Reader task
      writeln( "Reader: waiting to read." );
      var read_sync = someSyncVar$;
      writeln( "Reader: value is ", read_sync );
    }

    begin { // Writer task
      writeln( "Writer: will write in..." );
      countdown( 3 );
      someSyncVar$ = 123;
    }
  }

  // single vars can only be written once. A read on an unwritten single results
  // in a wait, but when the variable has a value it can be read indefinitely
  var someSingleVar$: single int; // varName$ is a convention not a law.
  sync {
    begin { // Reader task
      writeln( "Reader: waiting to read." );
      for i in 1..5 {
        var read_single = someSingleVar$;
        writeln( "Reader: iteration ", i,", and the value is ", read_single );
      }
    }

    begin { // Writer task
      writeln( "Writer: will write in..." );
      countdown( 3 );
      someSingleVar$ = 5; // first and only write ever.
    }
  }

  // Heres an example of using atomics and a synch variable to create a
  // count-down mutex (also known as a multiplexer)
  var count: atomic int; // our counter
  var lock$: sync bool;   // the mutex lock

  count.write( 2 );       // Only let two tasks in at a time.
  lock$.writeXF( true );  // Set lock$ to full (unlocked)
  // Note: The value doesnt actually matter, just the state
  // (full:unlocked / empty:locked)
  // Also, writeXF() fills (F) the sync var regardless of its state (X)

  coforall task in 1..#5 { // Generate tasks
    // Create a barrier
    do{
      lock$;                 // Read lock$ (wait)
    }while ( count.read() < 1 ); // Keep waiting until a spot opens up

    count.sub(1);          // decrement the counter
    lock$.writeXF( true ); // Set lock$ to full (signal)

    // Actual 'work'
    writeln( "Task #", task, " doing work." );
    sleep( 2 );

    count.add( 1 );        // Increment the counter
    lock$.writeXF( true ); // Set lock$ to full (signal)
  }

  // we can define the operations + * & | ^ && || min max minloc maxloc
  // over an entire array using scans and reductions
  // Reductions apply the operation over the entire array and
  // result in a single value
  var listOfValues: [1..10] int = [15,57,354,36,45,15,456,8,678,2];
  var sumOfValues = + reduce listOfValues;
  var maxValue = max reduce listOfValues; // 'max' give just max value

  // 'maxloc' gives max value and index of the max value
  // Note: We have to zip the array and domain together with the zip iterator
  var (theMaxValue, idxOfMax) = maxloc reduce zip(listOfValues,
                                                  listOfValues.domain);

  writeln( (sumOfValues, maxValue, idxOfMax, listOfValues[ idxOfMax ] ) );

  // Scans apply the operation incrementally and return an array of the
  // value of the operation at that index as it progressed through the
  // array from array.domain.low to array.domain.high
  var runningSumOfValues = + scan listOfValues;
  var maxScan = max scan listOfValues;
  writeln( runningSumOfValues );
  writeln( maxScan );
} // end main()
```

Who is this tutorial for?
-------------------------

This tutorial is for people who want to learn the ropes of chapel without having to hear about what fiber mixture the ropes are, or how they were braided, or how the braid configurations differ between one another.
It won't teach you how to develop amazingly performant code, and it's not exhaustive.
Refer to the [language specification](http://chapel.cray.com/language.html) and the [module documentation](http://chapel.cray.com/docs/latest/) for more details.

Occasionally check back here and on the [Chapel site](http://chapel.cray.com) to see if more topics have been added or more tutorials created.

### What this tutorial is lacking:

 * Exposition of the [standard modules](http://chapel.cray.com/docs/latest/modules/modules.html)
 * Multiple Locales (distributed memory system)
 * Records
 * Parallel iterators

Your input, questions, and discoveries are important to the developers!
-----------------------------------------------------------------------

The Chapel language is still in-development (version 1.12.0), so there are occasional hiccups with performance and language features.
The more information you give the Chapel development team about issues you encounter or features you would like to see, the better the language becomes.
Feel free to email the team and other developers through the [sourceforge email lists](https://sourceforge.net/p/chapel/mailman).

If you're really interested in the development of the compiler or contributing to the project,
[check out the master Github repository](https://github.com/chapel-lang/chapel).
It is under the [Apache 2.0 License](http://www.apache.org/licenses/LICENSE-2.0).

Installing the Compiler
-----------------------

Chapel can be built and installed on your average 'nix machine (and cygwin).
[Download the latest release version](https://github.com/chapel-lang/chapel/releases/)
and it's as easy as

 1. `tar -xvf chapel-1.12.0.tar.gz`
 2. `cd chapel-1.12.0`
 3. `make`
 4. `source util/setchplenv.bash # or .sh or .csh or .fish`

You will need to `source util/setchplenv.EXT` from within the Chapel directory (`$CHPL_HOME`) every time your terminal starts so it's suggested that you drop that command in a script that will get executed on startup (like .bashrc).

Chapel is easily installed with Brew for OS X

 1. `brew update`
 2. `brew install chapel`

Compiling Code
--------------

Builds like other compilers:

`chpl myFile.chpl -o myExe`

Notable arguments:

 * `--fast`: enables a number of optimizations and disables array bounds checks. Should only enable when application is stable.
 * `--set <Symbol Name>=<Value>`: set config param `<Symbol Name>` to `<Value>` at compile-time.
 * `--main-module <Module Name>`: use the main() procedure found in the module `<Module Name>` as the executable's main.
 * `--module-dir <Directory>`: includes `<Directory>` in the module search path.