If-then-else construct

For a conditional IF-THEN or IF-THEN-ELSE construction we can state the Rules of Conditional Statements ... 

Use switch construct instead of multiple, nested if-then-else statements, especially when all the conditionals are treated at the same level. The resulting code is usually easier to read and follow. However, when different types of conditionals are tested, multiple, nested if-then-else constructs are preferable. An example for using switch versus if statements is shown in Code Block 5 (Figure 2.5). 

At run time, a decision tree asks a series of questions in order, and based on the outcome of these delivers a label. In essence then, this is no more than series of nested if then else constructions in a computer program. For our cases, one set of questions might be if the token is lead and the following token is contains the string poison and if the token pollution or heavy is also foimd in the sentence then mark this as lead metal . 

IF-THEN ELSE constructs, in which the condition is an affine expression. 

Another construct for path selection is the if-then-else construct. This is used when the algorithm must select one of two different paths. For example ... 

The if-then and the if-then-else constructs are also useful in situations where the algorithm needs to select one of a number of alternatives. For example ... 

The two required constructs are (1) the general loop, and (2) the IF-THEN-ELSE. Neither of these constructs was included in the original BASIC. The FOR-NEXT is not a general loop because the conditions that determine its completion must be known ahead of time. Thus, with... 

To be sure, both the general loop and the general IF-THEN-ELSE can be constructed using GOTO and IF-THEN statements, but that is not the point. Programmers tend to make fewer errors when the language they are using provides the constructs they need to carry out their work. 

As the acceptance of structured programming grew, the reputation of BASIC declined. This was a fair assessment of most microcomputer versions of BASIC. Many of them added abbreviated constructs, such as the single-line IF-THEN and IF-THEN-ELSE discussed earlier, but these additions were often made with little thought as to how they would fit with other language features, such as multiple statements on a line. 

Existing pattern templates exist for common constructs such as assignment, procedure calls, loops, case, if-then-else and so on. 

Clearly, the first formula transfers control to the ELSE part if e is not true, while the second formula transfers control to the THEN part if e is true. Of course, other select constructs may be translated to IF-THEN-ELSE, or directly formalized in a similar manner. 

Control nodes Such nodes are used for building control structures, such as if then else or while-do constructs. 

Timing constraints and control flow. Timing constraints may be placed on any pair of operators in a behavioral specification. Evaluation of timing constraints must consider the possibility that two operations may be separated by conditionals and loops. In the case of conditionals, there may be more than one path of execution between the two operators. For example. Figure 5-4 shows two operations separated by a single IF-THEN-ELSE conditional construct. Since the two parts of the conditional may take different amounts of time to execute, any timing constraint on the two operators must be satisfied when either of the two paths is executed. When conditionals are nested, additional paths of execution are possible. CSTEP deals with this possibility in a preprocessing step that enumerates the paths between operators and creates a separate constraint for each path. 

While a sequence of commands in the Command Window can implanent many algorithms, it is awkward if selection (if-then-else) or repetition (e.g., while) logic is involved. The best way to do programming in MATLAB is to construct an M-flle (comparable to a VBA Macro). These are called M-flles since the automatic file type is. m. 

This indirect approach to modeling activity coefficients is used for at least two reasons (a) When we model g and evaluate the y, from (5.4.10), then the y,- automatically satisfy the Gibbs-Duhem equation (5.4.18). However, if we try to construct independent models for all the y, of a mixture, either the proposed equations for the y,- may fail to satisfy the Gibbs-Duhem equation or else an apparently simple form for one activity coefficient, yj, may lead to a complicated form for another, y2- ( ) For many mixtures, it is easier to develop accurate models for g than it is to directly develop accurate models for y,. Moreover, when the y, are obtained from a g model, the resulting expressions for the y, are often less complicated than forms devised by a direct modeling procedure. In this section we introduce two classes of models for g ... 

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