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* fix my messup!

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carl 2001-09-10 03:00:59 +00:00
parent fd7f76f801
commit d723294845
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docs/ref.tex
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@ -666,12 +666,10 @@ in mind:
\item The \var{Pred} and \var{Succ} functions cannot be used on \item The \var{Pred} and \var{Succ} functions cannot be used on
this kind of enumeration types. Trying to do this anyhow will result in a this kind of enumeration types. Trying to do this anyhow will result in a
compiler error. compiler error.
\item Enumeration types are by default stored using the same default size. This behaviour can be changed \item Enumeration types stored using a default size. This behaviour can be changed
with the \var{\{\$PACKENUM n\}} compiler directive, which with the \var{\{\$PACKENUM n\}} compiler directive, which
tells the compiler the minimal number of bytes to be used for enumeration tells the compiler the minimal number of bytes to be used for enumeration
types. More information can be found in the \progref, in the compiler directives types.
and memory issues sections.
For instance For instance
\begin{verbatim} \begin{verbatim}
Type Type
@ -692,7 +690,8 @@ Small enum : 1
Large enum : 4 Large enum : 4
\end{verbatim} \end{verbatim}
\end{enumerate} \end{enumerate}
More information can be found in the \progref, in the compiler directives
section.
\subsubsection{Subrange types} \subsubsection{Subrange types}
A subrange type is a range of values from an ordinal type (the {\em host} A subrange type is a range of values from an ordinal type (the {\em host}
type). To define a subrange type, one must specify it's limiting values: the type). To define a subrange type, one must specify it's limiting values: the
@ -752,8 +751,9 @@ When the single quote character must be represented, it should be typed
two times successively, thus \var{''''} represents the single quote character. two times successively, thus \var{''''} represents the single quote character.
\subsection{Strings} \subsection{Strings}
\fpc supports the \var{String} type as it is defined in Turbo Pascal and \fpc supports the \var{String} type as it is defined in Turbo Pascal
it supports ansistrings as in Delphi. (A sequence of characters with a specified length) and it
supports ansistrings as in Delphi.
To declare a variable as a string, use the following type specification: To declare a variable as a string, use the following type specification:
\input{syntax/sstring.syn} \input{syntax/sstring.syn}
@ -763,7 +763,7 @@ ansistrng or a short string.
Whatever the actual type, ansistrings and short strings can be used Whatever the actual type, ansistrings and short strings can be used
interchangeably. The compiler always takes care of the necessary type interchangeably. The compiler always takes care of the necessary type
coversions. Note, however, that the result of an expression that contains conversions. Note, however, that the result of an expression that contains
ansistrings and short strings will always be an ansistring. ansistrings and short strings will always be an ansistring.
\subsection{Short strings} \subsection{Short strings}
@ -782,11 +782,9 @@ The predefined type \var{ShortString} is defined as a string of length 255:
ShortString = String[255]; ShortString = String[255];
\end{verbatim} \end{verbatim}
For short strings \fpc reserves \var{Size+1} bytes for the string \var{S},
and in the zeroeth element of the string (\var{S[0]}) it will store the
length of the variable.
If the size of the string is not specified, \var{255} is taken as a If the size of the string is not specified, \var{255} is taken as a
default. default. The length of the string can be obtained with the \seef{Length}
standard runtime routine.
For example in For example in
\begin{verbatim} \begin{verbatim}
{$H-} {$H-}
@ -795,9 +793,8 @@ Type
NameString = String[10]; NameString = String[10];
StreetString = String; StreetString = String;
\end{verbatim} \end{verbatim}
\var{NameString} can contain maximum 10 characters. While \var{NameString} can contain a maximum of 10 characters. While
\var{StreetString} can contain 255 characters. The sizes of these variables \var{StreetString} can contain up to 255 characters.
are, respectively, 11 and 256 bytes.
\subsection{Ansistrings} \subsection{Ansistrings}
@ -809,23 +806,12 @@ counted. Internally, an ansistring is treated as a pointer.
If the string is empty (\var{''}), then the pointer is nil. If the string is empty (\var{''}), then the pointer is nil.
If the string is not empty, then the pointer points to a structure in If the string is not empty, then the pointer points to a structure in
heap memory that looks as in \seet{ansistrings}. heap memory.
\begin{FPCltable}{rl}{AnsiString memory structure}{ansistrings} It is possible to typecast an ansistring to a pchar.
Offset & Contains \\ \hline If the string is empty (so the pointer is nil) then the compiler
-12 & Longint with maximum string size. \\ makes sure that the typecasted pchar will point to a null byte. AnsiStrings
-8 & Longint with actual string size.\\ can be unlimited in length.
-4 & Longint with reference count.\\
0 & Actual string, null-terminated. \\ \hline
\end{FPCltable}
Because of this structure, it is possible to typecast an ansistring to a
pchar. If the string is empty (so the pointer is nil) then the compiler
makes sure that the typecasted pchar will point to a null byte.
AnsiStrings can be unlimited in length. Since the length is stored,
the length of an ansistring is available immediatly, providing for fast
access.
Assigning one ansistring to another doesn't involve moving the actual Assigning one ansistring to another doesn't involve moving the actual
string. A statement string. A statement
@ -868,14 +854,8 @@ statements:
then a copy of the string is created before the assignment. This is known then a copy of the string is created before the assignment. This is known
as {\em copy-on-write} semantics. as {\em copy-on-write} semantics.
It is impossible to access the length of an ansistring by referring to The \seef{Length} function must be used to get the length of an
the zeroeth character. The following statement will generate a compiler ansistring.
error if S is an ansistring:
\begin{verbatim}
Len:=S[0];
\end{verbatim}
Instead, the \seef{Length} function must be used to get the length of a
string.
To set the length of an ansistring, the \seep{SetLength} function must be used. To set the length of an ansistring, the \seep{SetLength} function must be used.
Constant ansistrings have a reference count of -1 and are treated specially. Constant ansistrings have a reference count of -1 and are treated specially.