Mercurial > urweb
comparison doc/manual.tex @ 2042:336070df8aec
Manual: Heuristic compilation warning
| author | Adam Chlipala <adam@chlipala.net> |
|---|---|
| date | Sat, 26 Jul 2014 09:39:45 -0400 |
| parents | 3d10ae22abd6 |
| children | ced78ef1c82f |
comparison
equal
deleted
inserted
replaced
| 2041:ec7a1fa5e88f | 2042:336070df8aec |
|---|---|
| 375 \item \cd{URWEB\_NUM\_THREADS}: alternative to the \cd{-t} command-line argument (currently used only by FastCGI) | 375 \item \cd{URWEB\_NUM\_THREADS}: alternative to the \cd{-t} command-line argument (currently used only by FastCGI) |
| 376 \item \cd{URWEB\_STACK\_SIZE}: size of per-thread stacks, in bytes | 376 \item \cd{URWEB\_STACK\_SIZE}: size of per-thread stacks, in bytes |
| 377 \item \cd{URWEB\_PQ\_CON}: when using PostgreSQL, overrides the compiled-in connection string | 377 \item \cd{URWEB\_PQ\_CON}: when using PostgreSQL, overrides the compiled-in connection string |
| 378 \end{itemize} | 378 \end{itemize} |
| 379 | 379 |
| 380 \subsection{A Word of Warning on Heuristic Compilation} | |
| 381 | |
| 382 For server-side code, Ur/Web follows an unusual compilation model, where not all type-correct programs can be compiled successfully, especially when using functions as data not known until runtime. See Section \ref{phases} for more detail. | |
| 383 | |
| 380 | 384 |
| 381 \section{Ur Syntax} | 385 \section{Ur Syntax} |
| 382 | 386 |
| 383 In this section, we describe the syntax of Ur, deferring to a later section discussion of most of the syntax specific to SQL and XML. The sole exceptions are the declaration forms for relations, cookies, and styles. | 387 In this section, we describe the syntax of Ur, deferring to a later section discussion of most of the syntax specific to SQL and XML. The sole exceptions are the declaration forms for relations, cookies, and styles. |
| 384 | 388 |
| 2553 \end{itemize} | 2557 \end{itemize} |
| 2554 | 2558 |
| 2555 When no \texttt{jsFunc} directive is present, the function is assumed to map to a JavaScript function of the same name, if used in a client-side context. | 2559 When no \texttt{jsFunc} directive is present, the function is assumed to map to a JavaScript function of the same name, if used in a client-side context. |
| 2556 | 2560 |
| 2557 | 2561 |
| 2558 \section{Compiler Phases} | 2562 \section{\label{phases}Compiler Phases} |
| 2559 | 2563 |
| 2560 The Ur/Web compiler is unconventional in that it relies on a kind of \emph{heuristic compilation}. Not all valid programs will compile successfully. Informally, programs fail to compile when they are ``too higher order.'' Compiler phases do their best to eliminate different kinds of higher order-ness, but some programs just won't compile. This is a trade-off for producing very efficient executables. Compiled Ur/Web programs use native C representations and require no garbage collection. | 2564 The Ur/Web compiler is unconventional in that it relies on a kind of \emph{heuristic compilation}. Not all valid programs will compile successfully. Informally, programs fail to compile when they are ``too higher order.'' Compiler phases do their best to eliminate different kinds of higher order-ness, but some programs just won't compile. This is a trade-off for producing very efficient executables. Compiled Ur/Web programs use native C representations and require no garbage collection. Also, this warning only applies to server-side code, as client-side code runs in a normal JavaScript environment with garbage collection. |
| 2561 | 2565 |
| 2562 In this section, we step through the main phases of compilation, noting what consequences each phase has for effective programming. | 2566 In this section, we step through the main phases of compilation, noting what consequences each phase has for effective programming. |
| 2563 | 2567 |
| 2564 \subsection{Parse} | 2568 \subsection{Parse} |
| 2565 | 2569 |