CODEWITHSUNDEEP
delphiprogramming-languages
Federico Zancan
Federico Zancan

Reputation: 4884

Delphi reserved words and identifiers

Declaring variables in Delphi brought me to consider a thing that I can't understand.

The question is this: declaring strings, one can observe that string is a reserved word, while declaring other data types, say integers, the data type qualifier is not a reserved word but an identifier (i.e. Integer, the capital I tells so).

In fact, Delphi lets you go to the definition of Integer, which you discover it is contained within the System unit, but it is only representative, because there is a comment stating that some constants (like True), identifiers (like Integer), functions and procedures are directly built into the compiler.

I can't figure out the reasons behind this choice.

Could someone help?

A little explanation of the difference between string and Integer types. The next code

type
  Integer = Char;

var
  I: Integer;

begin
  I:= 'A';
  ShowMessage(I);
end;

is correct and works as expected, while the next line

type
  string = Integer;

gives compile-time error.

Upvotes: 14

Views: 2272

Answers (2)

user743382
user743382

Reputation:

string must be a reserved word, because it is not exclusively used to refer to the type System.[Ansi|Unicode]String. If string were a simple alias for some internal compiler type, then string[20] would no longer work. This is not a problem for Integer, because Integer always means nothing more than "the type System.Integer".

Upvotes: 6

RRUZ
RRUZ

Reputation: 136401

As far i know string is a reserved word since the Turbo Pascal times. So the reason to keep it in this way must be for compatibility.

Pascal -> Turbo Pascal - > Object Pascal -> Delphi.

Check these resources.

Upvotes: 6

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