scsh-conservatory
/
scsh-0.6
1
0
Fork 0
Code Issues Pull Requests Packages Projects Releases Wiki Activity

Changed the module warning: Recommend the use of scheme-with-scsh.

This commit is contained in:
mainzelm 2002-12-06 14:06:41 +00:00
parent e47611a0ae
commit 2540846e92
1 changed files with 28 additions and 33 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

61
doc/scsh-manual/running.tex
View File

@ -146,40 +146,35 @@ all, we recommend taking the time to learn and use it.
The effort will pay off in the construction of modular, factorable programs. The effort will pay off in the construction of modular, factorable programs.
\subsubsection{Module warning} \subsubsection{Module warning}
Programmers who open both the \ex{scheme} and \ex{scsh} structures in their Most scsh programs will need to import from the \ex{scheme} structure
own packages should make sure to always put the \ex{scsh} reference first. as well as from the \ex{scsh} structure. However, putting both of
\begin{center} these structures in the same \texttt{open} clause is a bad idea
\begin{tabular}{l@{\qquad}l} because the structures \ex{scheme} and \ex{scsh} export some names of
Do this: & Not this: \strut \\ I/O functions in common but with different definitions. The current
\quad{\begin{codebox}[b] implementation of the module system does not recognize this as an
(define-structure web-server error but silently overwrites the exports of one structure with the
(open scsh exports of the other. If the \ex{scheme} structure overwrites the
scheme exports of the \ex{scsh} structures the program will access the
net-hax R$^5$RS definitions of the I/O functions which is not what you want.
\vdots)
(file web))\end{codebox}}
&
\quad{\begin{codebox}[b]
(define-structure web-server
(open scheme
scsh
net-hax
\vdots)
(file web))\end{codebox}}\\
%
Open \ex{scsh} before \ex{scheme}. &
Not \ex{scsh} after \ex{scheme}.
\end{tabular}
\end{center}
Ordering the two packages like this is necessary because scsh overrides
some of the standard R4RS Scheme definitions exported by the \ex{scheme}
package with its own definitions.
For example, scsh's versions of the R4RS I/O functions such as \ex{display}
and \ex{write} take integer file descriptors as arguments, as well as Scheme
ports.
If you open the \ex{scheme} structure before the \ex{scsh} structure,
you'll get the standard {\scm} definitions, which is not what you want.
Previous versions of this manual suggested to list \ex{scheme} and
\ex{scsh} in a specific order in the \texttt{open} clause of a
structure to ensure that the definitions from \ex{scsh} overwrite the
ones from \ex{scheme}. This approach is error-prone and fragile: A
simple change in the implementation of the module system will render
thousands of programs useless. Starting with release 0.6.3 scsh
provides a better means to deal with this problem: the structure
\ex{scheme-with-scsh} provides all the exports of the modules
\ex{scheme} and \ex{scsh} but exports the right denotations for the
I/O functions in question. To make a long story short:
\begin{center}
Scsh programs should open the structure \ex{scheme-with-scsh} if
they need access to the exports of \ex{scheme} and \ex{scsh}.
\end{center}
For programs which should run in versions of scsh prior to release
0.6.3, programmers should make sure to always put the \ex{scsh}
reference first.
\subsection{Switches} \subsection{Switches}
\label{sec:scsh-switches} \label{sec:scsh-switches}