Difference between revisions of "Declaration"

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== Syntax ==
 
== Syntax ==
  
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Variable declaration is a key part to any language. In order to declare a variable in Mesham the ''var'' keyword is used.
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All variables must be declared before they are used. In Mesham one may declare a variable via its value or explicit type.
  
 
var [varname];<br>
 
var [varname];<br>
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== Semantics ==
 
== Semantics ==
  
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In the case of a value being specified, the compiler will infer the type via type inference, also making the assumption that the variable is allocated on each process.
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The environment will map the identifier to storage location and that variable is now usable. In the case of a value being specified then the compiler will infer the type via type inference either here or when the first assignment takes place.<br><br>
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''Note:'' It is not possible to declare a variable with the value ''null'' as this is a special, no value, placer and as such has no type.
  
 
== Examples ==
 
== Examples ==
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  var b:=99;
 
  var b:=99;
 
  a:="hello";
 
  a:="hello";
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 +
In the code example above, the variable ''a'' is declared, without any further information the type is infered by its first use (to hold type String.) Variable ''b'' is declared with value 99, an integer and as such the type is infered to be both Int and allocated on multiple processes.
 +
 
  var t:Char;
 
  var t:Char;
 
  var z:Char :: allocated[single[on[2]]];
 
  var z:Char :: allocated[single[on[2]]];
  
−
In the code example above, the variable "a" is declared, without any further information the type is infered by its first use (to hold type String.) Variable "b" is declared with value 99, an integer and as such the type is infered to be both Int and allocated on multiple processes. "t" is declared to be a character, without further type information it is also assumed to be on all processes (the type Char is automatically coherced with the type allocated[multiple[]]. Lastly, the variable "z" is declared to be of type character, but is allocated only on a single process (process 2.)  
+
Variable ''t'' is declared to be a character, without further type information it is also assumed to be on all processes (by default the type Char is allocated to all processes.) Lastly, the variable ''z'' is declared to be of type character, but is allocated only on a single process (process 2.)  
  
 
[[Category:sequential]]
 
[[Category:sequential]]

Revision as of 13:58, 12 January 2013

Syntax

All variables must be declared before they are used. In Mesham one may declare a variable via its value or explicit type.

var [varname];
var [varname]:=[Value];
var [varname]:[Type];

Semantics

The environment will map the identifier to storage location and that variable is now usable. In the case of a value being specified then the compiler will infer the type via type inference either here or when the first assignment takes place.

Note: It is not possible to declare a variable with the value null as this is a special, no value, placer and as such has no type.

Examples

var a;
var b:=99;
a:="hello";

In the code example above, the variable a is declared, without any further information the type is infered by its first use (to hold type String.) Variable b is declared with value 99, an integer and as such the type is infered to be both Int and allocated on multiple processes. 

var t:Char;
var z:Char :: allocated[single[on[2]]];

Variable t is declared to be a character, without further type information it is also assumed to be on all processes (by default the type Char is allocated to all processes.) Lastly, the variable z is declared to be of type character, but is allocated only on a single process (process 2.)

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