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* fix my messup!
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docs/ref.tex
58
docs/ref.tex
@ -666,12 +666,10 @@ in mind:
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\item The \var{Pred} and \var{Succ} functions cannot be used on
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this kind of enumeration types. Trying to do this anyhow will result in a
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compiler error.
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\item Enumeration types are by default stored using the same default size. This behaviour can be changed
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\item Enumeration types stored using a default size. This behaviour can be changed
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with the \var{\{\$PACKENUM n\}} compiler directive, which
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tells the compiler the minimal number of bytes to be used for enumeration
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types. More information can be found in the \progref, in the compiler directives
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and memory issues sections.
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types.
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For instance
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\begin{verbatim}
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Type
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@ -692,7 +690,8 @@ Small enum : 1
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Large enum : 4
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\end{verbatim}
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\end{enumerate}
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More information can be found in the \progref, in the compiler directives
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section.
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\subsubsection{Subrange types}
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A subrange type is a range of values from an ordinal type (the {\em host}
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type). To define a subrange type, one must specify it's limiting values: the
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@ -752,8 +751,9 @@ When the single quote character must be represented, it should be typed
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two times successively, thus \var{''''} represents the single quote character.
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\subsection{Strings}
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\fpc supports the \var{String} type as it is defined in Turbo Pascal and
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it supports ansistrings as in Delphi.
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\fpc supports the \var{String} type as it is defined in Turbo Pascal
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(A sequence of characters with a specified length) and it
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supports ansistrings as in Delphi.
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To declare a variable as a string, use the following type specification:
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\input{syntax/sstring.syn}
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@ -763,7 +763,7 @@ ansistrng or a short string.
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Whatever the actual type, ansistrings and short strings can be used
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interchangeably. The compiler always takes care of the necessary type
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coversions. Note, however, that the result of an expression that contains
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conversions. Note, however, that the result of an expression that contains
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ansistrings and short strings will always be an ansistring.
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\subsection{Short strings}
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@ -782,11 +782,9 @@ The predefined type \var{ShortString} is defined as a string of length 255:
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ShortString = String[255];
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\end{verbatim}
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For short strings \fpc reserves \var{Size+1} bytes for the string \var{S},
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and in the zeroeth element of the string (\var{S[0]}) it will store the
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length of the variable.
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If the size of the string is not specified, \var{255} is taken as a
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default.
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default. The length of the string can be obtained with the \seef{Length}
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standard runtime routine.
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For example in
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\begin{verbatim}
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{$H-}
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@ -795,9 +793,8 @@ Type
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NameString = String[10];
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StreetString = String;
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\end{verbatim}
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\var{NameString} can contain maximum 10 characters. While
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\var{StreetString} can contain 255 characters. The sizes of these variables
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are, respectively, 11 and 256 bytes.
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\var{NameString} can contain a maximum of 10 characters. While
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\var{StreetString} can contain up to 255 characters.
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\subsection{Ansistrings}
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@ -809,23 +806,12 @@ counted. Internally, an ansistring is treated as a pointer.
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If the string is empty (\var{''}), then the pointer is nil.
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If the string is not empty, then the pointer points to a structure in
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heap memory that looks as in \seet{ansistrings}.
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heap memory.
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\begin{FPCltable}{rl}{AnsiString memory structure}{ansistrings}
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Offset & Contains \\ \hline
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-12 & Longint with maximum string size. \\
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-8 & Longint with actual string size.\\
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-4 & Longint with reference count.\\
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0 & Actual string, null-terminated. \\ \hline
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\end{FPCltable}
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Because of this structure, it is possible to typecast an ansistring to a
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pchar. If the string is empty (so the pointer is nil) then the compiler
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makes sure that the typecasted pchar will point to a null byte.
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AnsiStrings can be unlimited in length. Since the length is stored,
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the length of an ansistring is available immediatly, providing for fast
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access.
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It is possible to typecast an ansistring to a pchar.
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If the string is empty (so the pointer is nil) then the compiler
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makes sure that the typecasted pchar will point to a null byte. AnsiStrings
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can be unlimited in length.
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Assigning one ansistring to another doesn't involve moving the actual
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string. A statement
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@ -868,14 +854,8 @@ statements:
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then a copy of the string is created before the assignment. This is known
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as {\em copy-on-write} semantics.
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It is impossible to access the length of an ansistring by referring to
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the zeroeth character. The following statement will generate a compiler
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error if S is an ansistring:
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\begin{verbatim}
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Len:=S[0];
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\end{verbatim}
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Instead, the \seef{Length} function must be used to get the length of a
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string.
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The \seef{Length} function must be used to get the length of an
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ansistring.
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To set the length of an ansistring, the \seep{SetLength} function must be used.
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Constant ansistrings have a reference count of -1 and are treated specially.
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