Begin-End for Grouping Expressions

Revision as of 00:17, 5 January 2017 by Lchrisman (talk | contribs) (Local Variables --> Local Values (terminology change))

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 :=
Var v := Array(Dim, [X, Y]);
Var v_r := sum(rot*v, Dim);
X_rot := v_r[Dim2 = 'x'];
v_r[Dim2 = 'y'];

Grouping with parentheses:

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

See Also


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