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Chapel Tutorial

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+---
+language: chapel
+filename: learnchapel.chpl
+contributors:
+    - ["Ian J. Bertolacci", "http://www.cs.colostate.edu/~ibertola/"]
+lang: en
+---
+
+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.
+
+```chapel
+// 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 dont 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; // define mySecondVar as a 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
+// Like consts, they cannot be changed during runtime
+param compileTimeConst: int = 16;
+
+// The config modifier allows values to be set at the command line
+// and is much easier that 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 at compile time
+config param paramCmdLineArg: bool = false;
+writeln( varCmdLineArg, ", ", constCmdLineArg, ", ", paramCmdLineArg );
+// Set config with --set paramCmdLineArg=value at compile time
+
+// 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 dont 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" );
+    writeln( "Oh, and when statements dont cascade like the case statements" );
+    writeln( "of other languages" );
+  }
+}
+
+// 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 indicies 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
+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 ); 
+
+// 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] );
+
+// 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 dont 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 tupe 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( );
+
+// 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 dont 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 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
+  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( );
+
+// Parallelism
+// In other languages, parallelism is typically this is 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
+
+// A succinct way of writing a forall loop over an array:
+// iterate over values
+[ val in myBigArray ] val = 1 / val; 
+// or iterate over indicies
+[ idx in myBigArray.domain ] myBigArray[idx] = -myBigArray[idx]; 
+```
+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 [library 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:
+ * Modules and standard modules
+ * Synchronize and atomic variables
+ * Multiple Locales (distributed memory system)
+ * ```proc main(){ ... }```
+ * Records
+ * Whole/sliced array assignment
+ * Reductions and scans
+ * Range and domain slicing
+ * Parallel iterators
+
+Your input, questions, and discoveries are important to the developers!
+-----------------------------------------------------------------------
+The Chapel language is still in-development (version 1.11.0), 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 its as easy as 
+ 1. ```tar -xvf chapel-1.11.0.tar.gz```
+ 2. ```cd chapel-1.11.0```
+ 3. ```make```
+ 4. ```source util/setchplenv.bash # or .sh or .csh or .fish```
+
+You will need to ```source util/setchplenv.EXT``` from the chapel directory every time your terminal starts so its 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```
+
+A notable argument:
+ * ``--fast``: enables a number of optimizations and disables array bounds checks. Should only enable when application is stable.