Difference between revisions of "Begin-End for Grouping Expressions"
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<breadcrumbs> Analytica User Guide > Procedural Programming > {{PAGENAME}}</breadcrumbs><br />
 
<breadcrumbs> Analytica User Guide > Procedural Programming > {{PAGENAME}}</breadcrumbs><br />
  
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As illustrated above, you can group several expressions (statements) as the definition of a variable or function simply by separating them by semicolons (<code>;</code>). To group several expressions as a condition or action of <code>If a Then b Else c</code> or <code>While a Do b</code>, or, indeed, anywhere a single expression is valid, you should enclose the expressions between <code>Begin</code> and <code>End</code>, or between parentheses characters <code>(</code> and <code>)</code>.  For example:
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As illustrated above, you can group several expressions (statements) as the definition of a variable or function simply by separating them by semicolons (<code>;</code>). To group several expressions as a condition or action of [[IF a THEN b ELSE c|If a Then b Else c]] or [[For_and_While_Loops#While.28Test.29_Do_Body|While a Do b]], or, indeed, anywhere a single expression is valid, you should enclose the expressions between <code>Begin</code> and <code>End</code>, or between parentheses characters <code>(</code> and <code>)</code>.  For example:
  
 
Grouping with <code>Begin</code> and <code>End</code>:
 
Grouping with <code>Begin</code> and <code>End</code>:
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:<code>Variable rot := ... { a 2-D rotation matrix indexed by Dim and Dim2 }</code>
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Variable rot := ... { a 2-D rotation matrix indexed by Dim and Dim2 }
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:<code>Variable X_rot := ComputedBy(Y_rot)</code>
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:<code>Variable Y_rot :=</code>
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Variable X_rot := [[ComputedBy]](Y_rot)
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::<code>BEGIN</code>
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::<code>Var v := Array(Dim, [X, Y]);</code>
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Variable Y_rot :=
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::<code>Var v_r := sum(rot*v, Dim);</code>
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    [[Begin]]
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::<code>X_rot := v_r[Dim2 = 'x'];</code>
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          [[Local]] v := [[Array]](Dim, [X, Y]);
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::<code>v_r[Dim2 = 'y'];</code>
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          [[Local]] v_r := [[Sum]](rot*v, Dim);
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::<code>END</code>
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          X_rot := v_r[Dim2 = 'x'];
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          v_r[Dim2 = 'y'];
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    [[End]]
  
 
Grouping with parentheses:
 
Grouping with parentheses:
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<pre style="background:white; border:white; margin-left: 1em;">
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Function Table_to_array(A : Array[Rows, Columns] ; Rows, Columns: IndexType)
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Function Table_to_array(A : Array[Rows, Columns] ; Rows, Columns: IndexType)  
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Definition:
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Definition:
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  MetaIndex Inds :=
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    [[LocalIndex]] Inds :=
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      (
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      (
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        For c := 1..Size(Columns)-1 do (
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          [[For]] c := 1..[[IndexLength]](Columns)-1 Do (
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            Var v := A[@Columns = c];
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            [[Local]] v := A[@Columns = c];
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            Index I / Slice(Columns,c) := v[Rows = Unique(v, Rows)];
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            [[LocalIndex]] I / [[Slice]](Columns,c) := v[Rows = [[Unique]](v, Rows)];
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            VarTerm(I)
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            [[Handle]](I)
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        )
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          )
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      );
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      );
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      MdTable(A, Rows, Columns, inds)
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      [[MdTable]](A, Rows, Columns, inds)
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</pre>
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The overall value of the group of statements is the value from evaluating the last expression. For example:  
 
The overall value of the group of statements is the value from evaluating the last expression. For example:  
  
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:<code>(VAR x := 10; x := x/2; x - 2) → 3</code>
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:<code>([[Local]] x := 10; x := x/2; x - 2) → 3</code>
  
 
Analytica also tolerates a semicolon (<code>;</code>) after the last expression in a group. It still returns the value of the last expression. For example:
 
Analytica also tolerates a semicolon (<code>;</code>) after the last expression in a group. It still returns the value of the last expression. For example:
  
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:<code>(VAR x := 10; x := x/2; x/2;) → 2.5</code>
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:<code>([[Local]] x := 10; x := x/2; x/2;) → 2.5</code>
  
 
The statements can be grouped on one line, or over several lines. In fact, Analytica does not care where new-lines, spaces, or tabs occur within an expression or sequence of expressions — as long as they are not within a number or identifier.
 
The statements can be grouped on one line, or over several lines. In fact, Analytica does not care where new-lines, spaces, or tabs occur within an expression or sequence of expressions — as long as they are not within a number or identifier.
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<footer>Summary of Programming Constructs / {{PAGENAME}} / Local Variables</footer>
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<footer>Summary of Programming Constructs / {{PAGENAME}} / Local Values</footer>

Latest revision as of 23:09, 3 July 2024


Analytica User GuideProcedural ProgrammingBegin-End for Grouping Expressions


As illustrated above, you can group several expressions (statements) as the definition of a variable or function simply by separating them by semicolons (;). To group several expressions as a condition or action of If a Then b Else c or While a Do b, or, indeed, anywhere a single expression is valid, you should enclose the expressions between Begin and End, or between parentheses characters ( and ). For example:

Grouping with Begin and End: 

Variable rot := ... { a 2-D rotation matrix indexed by Dim and Dim2 }

Variable X_rot := ComputedBy(Y_rot)

Variable Y_rot :=
    Begin
         Local v := Array(Dim, [X, Y]);
         Local v_r := Sum(rot*v, Dim);
         X_rot := v_r[Dim2 = 'x'];
         v_r[Dim2 = 'y'];
    End

Grouping with parentheses: 

Function Table_to_array(A : Array[Rows, Columns] ; Rows, Columns: IndexType) 
Definition:
   LocalIndex Inds :=
      (
         For c := 1..IndexLength(Columns)-1 Do (
            Local v := A[@Columns = c];
            LocalIndex I / Slice(Columns,c) := v[Rows = Unique(v, Rows)];
            Handle(I)
         )
      );
      MdTable(A, Rows, Columns, inds)

The overall value of the group of statements is the value from evaluating the last expression. For example:

(Local x := 10; x := x/2; x - 2) → 3

Analytica also tolerates a semicolon (;) after the last expression in a group. It still returns the value of the last expression. For example:

(Local x := 10; x := x/2; x/2;) → 2.5

The statements can be grouped on one line, or over several lines. In fact, Analytica does not care where new-lines, spaces, or tabs occur within an expression or sequence of expressions — as long as they are not within a number or identifier.

See Also


Summary of Programming ConstructsBegin-End for Grouping ExpressionsLocal Values
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