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

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.

@@ Line 1: / Line 1: @@
 [[Category: Analytica User Guide]]
-<breadcrumbs> Analytica User Guide > {{PAGENAME}}</breadcrumbs><br />
+[[Category: Expressions]]
-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
+<breadcrumbs> Analytica User Guide > Procedural Programming > {{PAGENAME}}</breadcrumbs><br />
-is valid, you should enclose the expressions between <code>Begin</code> and <code>End</code>, or between parentheses characters <code>(</code> and <code>)</code>.
+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>:
+ 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:
-:<code>(VAR x := 10; x := x/2; x - 2) → 3</code>
+:<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:
-:<code>(VAR x := 10; x := x/2; x/2;) → 2.5</code>
+:<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.
+==See Also==
+* [[Expression Syntax]]
+* [[Expression Assist]]
+* [[The Expression popup menu]]
-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.<br />
-<footer>Summary of Programming Constructs / {{PAGENAME}} / Local Variables</footer>
+<footer>Summary of Programming Constructs / {{PAGENAME}} / Local Values</footer>