Difference between revisions of "Begin-End for Grouping Expressions"

Revision as of 00:17, 5 January 2017

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

Var v := Array(Dim, [X, Y]);

Var 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:
   MetaIndex Inds :=
      (
         For c := 1..Size(Columns)-1 do (
            Var v := A[@Columns = c];
            Index I / Slice(Columns,c) := v[Rows = Unique(v, Rows)];
            VarTerm(I)
         )
      );
      MdTable(A, Rows, Columns, inds)

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

(VAR 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:

(VAR 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.

@@ Line 1: / Line 1: @@
 [[Category: Analytica User Guide]]
+[[Category: Expressions]]
 <breadcrumbs> Analytica User Guide > Procedural Programming > {{PAGENAME}}</breadcrumbs><br />
-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:
+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>:
@@ Line 16: / Line 18: @@
 Grouping with parentheses:
-:<code>Function Table_to_array(A : Array[Rows, Columns] ; Rows, Columns: IndexType)</code>
+<pre style="background:white; border:white; margin-left: 1em;">
-:<code>Definition:</code>
+Function Table_to_array(A : Array[Rows, Columns] ; Rows, Columns: IndexType)
-::<code>MetaIndex Inds :=</code>
+Definition:
-:::<code>(</code>
+   MetaIndex Inds :=
-::::<code>For c := 1..Size(Columns)-1 do (</code>
+      (
-:::::<code>Var v := A[@Columns = c];</code>
+         For c := 1..Size(Columns)-1 do (
-:::::<code>Index I / Slice(Columns,c) := v[Rows = Unique(v, Rows)];</code>
+            Var v := A[@Columns = c];
-:::::<code>VarTerm(I)</code>
+            Index I / Slice(Columns,c) := v[Rows = Unique(v, Rows)];
-::::<code>)</code>
+            VarTerm(I)
-:::<code>);</code>
+         )
-:::<code>MdTable(A, Rows, Columns, inds)</code>
+      );
+      MdTable(A, Rows, Columns, inds)
+</pre>
 The overall value of the group of statements is the value from evaluating the last expression. For example:
@@ Line 37: / Line 41: @@
 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.
-<footer>Summary of Programming Constructs / {{PAGENAME}} / Local Variables</footer>
+==See Also==
+* [[Expression Syntax]]
+* [[Expression Assist]]
+* [[The Expression popup menu]]
+<footer>Summary of Programming Constructs / {{PAGENAME}} / Local Values</footer>