doc/vala/statements.xml

   1 <?xml version="1.0"?>
   2 <section id="statements">
   3         <h>Statements</h>
   4         <section id="selection">
   5                 <h>Selection statements</h>
   6                 <p>The if statement selects a statement for execution based on the value of a boolean expression.</p>
   7                 <blockquote>
   8 if-statement:
   9         <l>if (</l> boolean-expression <l>)</l> embedded-statement
  10         <l>if (</l> boolean-expression <l>)</l> embedded-statement <l>else</l> embedded-statement
  11                 </blockquote>
  12         </section>
  13         <section id="iteration">
  14                 <h>Iteration statements</h>
  15                 <p>The while statement conditionally executes an embedded statement zero or more times.</p>
  16                 <blockquote>
  17 while-statement:
  18         <l>while (</l> boolean-expression <l>)</l> embedded-statement
  19                 </blockquote>
  20                 <p>The do statement conditionally executes an embedded statement one or more times.</p>
  21                 <blockquote>
  22 do-statement:
  23         <l>do</l> embedded-statement <l>while (</l> boolean-expression <l>) ;</l>
  24                 </blockquote>
  25                 <p>The for statement evaluates a sequence of initialization expressions and then, while a condition is true, repeatedly executes an embedded statement and evaluates a sequence of iteration expressions.</p>
  26                 <blockquote>
  27 for-statement:
  28         <l>for (</l> [for-initializer] <l>;</l> [for-condition] <l>;</l> [for-iterator] <l>)</l> embedded-statement
  29
  30 for-initializer:
  31         local-variable-declaration
  32         statement-expression-list
  33
  34 for-condition:
  35         boolean-expression
  36
  37 for-iterator:
  38         statement-expression-list
  39
  40 statement-expression-list:
  41         statement-expression
  42         statement-expression-list <l>,</l> statement-expression
  43                 </blockquote>
  44                 <p>Within the embedded statement of a for statement, a break statement can be used to transfer control to the end point of the for statement (thus ending iteration of the embedded statement), and a continue statement can be used to transfer control to the end point of the embedded statement (thus executing another iteration of the for statement).</p>
  45                 <p>The foreach statement enumerates the elements of a collection, executing an embedded statement for each element of the collection.</p>
  46                 <blockquote>
  47 foreach-statement:
  48         <l>foreach (</l> type identifier <l>in</l> expression <l>)</l> embedded-statement
  49                 </blockquote>
  50         </section>
  51         <section id="jump">
  52                 <h>Jump statements</h>
  53                 <p>The break statement exits the nearest enclosing switch, while, do, for, or foreach statement.</p>
  54                 <blockquote>
  55 break-statement:
  56         <l>break ;</l>
  57                 </blockquote>
  58                 <p>The continue statement starts a new iterataion of the nearest enclosing while, do, for, or foreach statement.</p>
  59                 <blockquote>
  60 continue-statement:
  61         <l>continue ;</l>
  62                 </blockquote>
  63                 <p>When multiple while, do, for, or foreach statements are nested within each other, a continue statement applies only to the innermost statement. If a continue statement is not eclosed by a while, do, for, or foreach statement, a compile-time error occurs.</p>
  64                 <p>The return statement returns control to the caller of the function member in which the return statement appears.</p>
  65                 <blockquote>
  66 return-statement:
  67         <l>return</l> [expression] <l>;</l>
  68                 </blockquote>
  69                 <p>The throw statement throws an exception.</p>
  70                 <blockquote>
  71 throw-statement:
  72         <l>throw</l> expression <l>;</l>
  73                 </blockquote>
  74         </section>
  75         <section id="try">
  76                 <h>Try statement</h>
  77                 <p>The try statement provides a mechanism for catching exceptions that occur during execution of a block. Furthermore, the try statement provides the ability to specify a block of code that is always executed when control leaves the try statement.</p>
  78                 <blockquote>
  79 try-statement:
  80         <l>try</l> block catch-clauses
  81         <l>try</l> block [catch-clauses] finally-clause
  82
  83 catch-clauses:
  84         specific-catch-clause
  85         [specific-catch-clauses] general-catch-clause
  86
  87 specific-catch-clause:
  88         specific-catch-clause
  89         specific-catch-clauses specific-catch-clause
  90
  91 specific-catch-clause:
  92         <l>catch (</l> error-type identifier <l>)</l> block
  93
  94 general-catch-clause:
  95         <l>catch</l> block
  96
  97 finally-clause:
  98         <l>finally</l> block
  99                 </blockquote>
 100         </section>
 101 </section>
 102