Difference between revisions of "Basic Pascal Tutorial/Chapter 3/CASE"
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3Cb - CASE (author: Tao Yue, state: changed) | 3Cb - CASE (author: Tao Yue, state: changed) | ||
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Suppose you wanted to branch one way if <tt>b</tt> is <tt>1, 7, 2037,</tt> or <tt>5</tt>; and another way if otherwise. You could do it by: | Suppose you wanted to branch one way if <tt>b</tt> is <tt>1, 7, 2037,</tt> or <tt>5</tt>; and another way if otherwise. You could do it by: | ||
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if (b = 1) or (b = 7) or (b = 2037) or (b = 5) then | if (b = 1) or (b = 7) or (b = 2037) or (b = 5) then | ||
Statement1 | Statement1 | ||
else | else | ||
Statement2; | Statement2; | ||
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But in this case, it would be simpler to list the numbers for which you want Statement1 to execute. You would do this with a <tt>case</tt> statement: | But in this case, it would be simpler to list the numbers for which you want Statement1 to execute. You would do this with a <tt>case</tt> statement: | ||
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case b of | case b of | ||
1,7,2037,5: Statement1; | 1,7,2037,5: Statement1; | ||
otherwise Statement2 | otherwise Statement2 | ||
end; | end; | ||
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The general form of the <tt>case</tt> statement is: | The general form of the <tt>case</tt> statement is: | ||
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case selector of | case selector of | ||
List1: Statement1; | List1: Statement1; | ||
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otherwise Statement | otherwise Statement | ||
end; | end; | ||
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The <tt>otherwise</tt> part is optional. When available, it differs from compiler to compiler. In many compilers, you use the word <tt>else</tt> instead of <tt>otherwise</tt>. | The <tt>otherwise</tt> part is optional. When available, it differs from compiler to compiler. In many compilers, you use the word <tt>else</tt> instead of <tt>otherwise</tt>. | ||
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Note that the lists must consist of literal values. That is, you must use constants or hard-coded values -- you cannot use variables. | Note that the lists must consist of literal values. That is, you must use constants or hard-coded values -- you cannot use variables. | ||
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Revision as of 02:33, 7 February 2020
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3Cb - CASE (author: Tao Yue, state: changed)
Case opens a case statement. The case statement compares the value of ordinal expression to each selector, which can be a constant, a subrange, or a list of them separated by commas. Selector field separated to action field by Colon.
Suppose you wanted to branch one way if b is 1, 7, 2037, or 5; and another way if otherwise. You could do it by:
if (b = 1) or (b = 7) or (b = 2037) or (b = 5) then
Statement1
else
Statement2;
But in this case, it would be simpler to list the numbers for which you want Statement1 to execute. You would do this with a case statement:
case b of
1,7,2037,5: Statement1;
otherwise Statement2
end;
The general form of the case statement is:
case selector of
List1: Statement1;
List2: Statement2;
...
Listn: Statementn;
otherwise Statement
end;
The otherwise part is optional. When available, it differs from compiler to compiler. In many compilers, you use the word else instead of otherwise.
selector is any variable of an ordinal data type. You may not use reals!
Note that the lists must consist of literal values. That is, you must use constants or hard-coded values -- you cannot use variables.
