A constant expression is an expression that the compiler can evaluate without executing the program in which it occurs. Constant expressions include numerals; character strings; true constants; values of enumerated types; the special constants True, False, and nil; and expressions built exclusively from these elements with operators, typecasts, and set constructors. Constant expressions cannot include variables, pointers, or function calls, except calls to the following predefined functions:
AbsHigh LowPred Succ ChrLengthOddRound Swap Hi Lo OrdSizeOfTrunc
This definition of a constant expression is used in several places in Delphi's syntax specification. Constant expressions are required for initializing global variables, defining subrange types, assigning ordinalities to values in enumerated types, specifying default parameter values, writing case statements, and declaring both true and typed constants.
Examples of constant expressions:
(2.5 + 1) / (2.5 - 1) 'Borland' + ' ' + 'Developer' Chr(32)
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