How to resolve the algorithm Short-circuit evaluation step by step in the Visual FoxPro programming language

Published on 12 May 2024 09:40 PM
#Visual foxpro

How to resolve the algorithm Short-circuit evaluation step by step in the Visual FoxPro programming language

Table of Contents

Problem Statement

Assume functions   a   and   b   return boolean values,   and further, the execution of function   b   takes considerable resources without side effects, and is to be minimized. If we needed to compute the conjunction   (and): Then it would be best to not compute the value of   b()   if the value of   a()   is computed as   false,   as the value of   x   can then only ever be   false. Similarly, if we needed to compute the disjunction (or): Then it would be best to not compute the value of   b()   if the value of   a()   is computed as   true,   as the value of   y   can then only ever be   true. Some languages will stop further computation of boolean equations as soon as the result is known, so-called   short-circuit evaluation   of boolean expressions

Create two functions named   a   and   b,   that take and return the same boolean value. The functions should also print their name whenever they are called. Calculate and assign the values of the following equations to a variable in such a way that function   b   is only called when necessary: If the language does not have short-circuit evaluation, this might be achieved with nested     if     statements.

Let's start with the solution:

Step by Step solution about How to resolve the algorithm Short-circuit evaluation step by step in the Visual FoxPro programming language

Source code in the visual programming language

*!* Visual FoxPro natively supports short circuit evaluation
CLEAR
CREATE CURSOR funceval(arg1 L, arg2 L, operation V(3), result L, calls V(10))
*!* Conjunction
INSERT INTO funceval (arg1, arg2, operation) VALUES (.F., .F., "AND")
REPLACE result WITH (a(arg1) AND b(arg2))
INSERT INTO funceval (arg1, arg2, operation) VALUES (.F., .T., "AND")
REPLACE result WITH (a(arg1) AND b(arg2))
INSERT INTO funceval (arg1, arg2, operation) VALUES (.T., .F., "AND")
REPLACE result WITH (a(arg1) AND b(arg2))
INSERT INTO funceval (arg1, arg2, operation) VALUES (.T., .T., "AND")
REPLACE result WITH (a(arg1) AND b(arg2))
*!* Disjunction
INSERT INTO funceval (arg1, arg2, operation) VALUES (.F., .F., "OR")
REPLACE result WITH (a(arg1) OR b(arg2))
INSERT INTO funceval (arg1, arg2, operation) VALUES (.F., .T., "OR")
REPLACE result WITH (a(arg1) OR b(arg2))
INSERT INTO funceval (arg1, arg2, operation) VALUES (.T., .F., "OR")
REPLACE result WITH (a(arg1) OR b(arg2))
INSERT INTO funceval (arg1, arg2, operation) VALUES (.T., .T., "OR")
REPLACE result WITH (a(arg1) OR b(arg2))
GO TOP

_VFP.DataToClip("funceval", 8, 3)

FUNCTION a(v As Boolean) As Boolean
REPLACE calls WITH "a()"
RETURN v
ENDFUNC

FUNCTION b(v As Boolean) As Boolean
REPLACE calls WITH calls + ", b()"
RETURN v
ENDFUNC

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