Difference between revisions of "String"

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== Example ==
 
== Example ==
  
  var i:String;
+
  function void main() {
var p:="Hello World!";
+
    var i:String;
 +
    var p:="Hello World!";
 +
};
  
 
In this example variable ''i'' is explicitly declared to be of type ''String''. Variable ''p'' is found, via type inference, also to be of type ''String''.
 
In this example variable ''i'' is explicitly declared to be of type ''String''. Variable ''p'' is found, via type inference, also to be of type ''String''.

Latest revision as of 15:44, 15 April 2019

Syntax

String

Semantics

A string of characters. All strings are immutable, concatenation of strings will in fact create a new string.

Default typing

In the absence of further type information, the following types are added to the chain:

Example

function void main() {
   var i:String;
   var p:="Hello World!";
};

In this example variable i is explicitly declared to be of type String. Variable p is found, via type inference, also to be of type String.

Since: Version 0.41b

Communication

When a variable is assigned to another, depending on where each variable is allocated to, there may be communication required to achieve this assignment. Table \ref{tab:eltypecomm} details the communication rules in the assignment \emph{assignmed variable := assigning variable}. If the communication is issued from MPMD programming style then this will be one sided. The default communication listed here is guaranteed to be safe, which may result in a small performance hit.


Assigned Variable Assigning Variable Semantics
multiple[] multiple[] local assignment
single[on[i]] multiple[] individual processes write values to process i
multiple[] single[on[i]] individual processes read values from process i
single[on[i]] single[on[i]] local assignment where i==i
single[on[i]] single[on[j]] communication from j to i where i!=j

Communication Example

var a:Int;
var b:Int :: allocated[single[on[2]]];
var p;
par p from 0 to 3 {
   if (p==2) b:=p;
   a:=b;
   sync;
};


This code will result in each process reading the value of b from process 2 and then writing this into a. As already noted, in absence of allocation information the default of allocating to all processes is used. In this example the variable a can be assumed to additionally have the type allocated[multiple]. Note that communication groups are the same as multiple in this context and share the same semantics. All variables marked multiple are private to their containing process.