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## 6. Compiling files and libraries

This chapter explains how you can use Larceny to compile Scheme source code to native machine code.

The native varieties of Larceny have a just-in-time compiler that compiles to native code automatically whenever you evaluate an expression, load a source file, or import a source library. Even so, files will load faster if they are compiled ahead of time.

Petit Larceny does not have a just-in-time compiler, so compiling ahead of time is the only way to enjoy the speed of native machine code in Petit Larceny.

Common Larceny uses an interpreter for expressions that are typed at the interactive read/eval/print loop, but files will be compiled as they are loaded if you specify `Larceny.fasl` on the command line. For more information on compiling files in Common Larceny, please consult the Common Larceny User Manual.

The main disadvantage of compiling files and libraries is that compiled code goes stale when its original source code is changed or when a library on which the compiled code depends is changed or recompiled. Stale compiled code can be dangerously inconsistent with libraries on which it depends, so Larceny checks for staleness and refuses to execute a stale library or program.

### 6.1. Compiling ERR5RS/R6RS libraries

On Unix machines, the most convenient way to compile a group of ERR5RS/R6RS libraries and top-level programs is to use the `compile-stale` script in Larceny's root directory. If Larceny's root directory is in your execution path, then there are just two steps:

1. Use `cd` to change to the directory that contains the ERR5RS/R6RS files you want to compile. (Files that lie within subdirectories of that directory will be compiled also.)
2. Run the `compile-stale` script.

For example:

        % cd lib/R6RS
        % compile-stale

On non-Unix machines, you can accomplish the same thing using Larceny's ERR5RS mode and the `(larceny compiler)` library:

        % pushd lib\R6RS
        % ..\..\larceny.bat -err5rs
        Larceny v0.96 "Fluoridation"
        ERR5RS mode (no libraries have been imported)

        > (import (larceny compiler))

        > (compile-stale-libraries)

To compile individual files, use the `compile-file` or `compile-library` procedures that are exported by `(larceny compiler)`.

### 6.2. Compiling R5RS source files

Procedure compile-file

`(compile-file sourcefile)`

Compiles sourcefile, which must be a string naming a file that contains R5RS source code. If faslfile is supplied as a second argument, then it must be a string naming the file that will contain the compiled code; otherwise the name of the compiled file is obtained from sourcefile by replacing the "`.sch`" or "`.scm`" suffix with "`.fasl`".

For ERR5RS/R6RS libraries and top-level programs, see above.

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