| pred | predecessor function |
| Syntax | pred ( expn )
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| Description | The pred function accepts an integer, character, or an enumerated value and returns the integer minus one, the previous character, or the previous value in the enumeration. For example, pred ( 7 ) is 6.
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| Example | This part of a Turing program fills up array a with the enumerated values red, yellow, green, red, yellow, green, etc.
type colors : enum ( green, yellow, red )
var a : array 1 .. 100 of colors
var c : colors := colors . red
for i : 1 .. 100
a ( i ) := c
if c = colors . green then
c := colors . red
else
c := pred ( c )
end if
end for
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| Details | It is illegal to apply pred to the first value of an enumeration.
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| See also | succ, lower and upper functions.
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