Procedural Programming Example

Analytica User GuideProcedural ProgrammingProcedural Programming Example

This function, Factors(x), computes the prime factors of an integer «x». It illustrates many of Analytica's key constructs for procedural programming:

This table identifies key constructs from the function definition above, with a number

Numbers identify features below	Function Factors(x) Definition:
1	VAR result := [1];
2	VAR n := 2;
3	WHILE n <= x DO
4	BEGIN
2	VAR r := Floor(x/n); IF r*n = x THEN
5	(result := Concat(result, [n]);x := r)
6	ELSE n := n + 1
4, 7	END;
7, 8	result /* End Definition */

This definition illustrates these features:

1. VAR x := e defines a local identifier x that refers to the value obtained by evaluating e. See Defining a Local Value.
2. You can group several expressions (statements) into a definition by separating them using “;” (semicolons). Expressions can be on the same line or successive lines. See Begin-End for Grouping Expressions.
3. While test Do body tests condition Test, and, if True, evaluates Body, and repeats until condition Test is False. See While(Test) Do Body.
4. BEGIN e1; e2; … ENDgroups a sequence of expressions separated by semicolons “;” — in this case as the body of a While loop. See Begin-End for Grouping Expressions.
5. (e1; e2; …) is another way to group expressions — in this case, as the action to be taken in the Then case. See Begin-End for Grouping Expressions.
6. x := e assigns the value of expression e to a local value x or, as in the first case, to a parameter of a function. See Assigning to a local value.
7. You can add a comment (text that Analytica ignores) between { and } or between /* and */.
8. The value returned from a group of expressions is the value of the last expression — here the function Factors returns the local value result — whether the group is delimited by Begin and End, by parentheses, ( and ), or, as here, by nothing.

See Also

• Defining a Local Value
• Assigning to a local value
• Begin-End for Grouping Expressions
• For and While Loops
• Function calls and parameters

Procedural ProgrammingProcedural Programming ExampleSummary of Programming Constructs