Chapter 39

restart.ss: Simulating Stand-alone MzScheme

To load: (require (lib "restart.ss"))

(restart-mzscheme init-argv adjust-flag-table argv init-namespace)      PROCEDURE

Simulates starting the stand-alone version of MzScheme with the vector of command-line strings argv. The init-argv, adjust-flag-table, and init-namespace arguments are used to modify the default settings for command-line flags, adjust the parsing of command-line flags, and customize the initial namespace, respectively.

The vector of strings init-argv is read first with the standard MzScheme command-line parsing. Flags that load files or evaluate expressions (e.g., -f and -e) are ignored, but flags that set MzScheme's modes (e.g., -g or -m) effectively set the default mode before argv is parsed.

Before argv is parsed, the procedure adjust-flag-table is called with a command-line flag table as accepted by parse-command-line (see section 10). The return value must also be a table of command-line flags, and this table is used to parse argv. The intent is to allow adjust-flag-table to add or remove flags from the standard set.

After argv is parsed, a new thread and a namespace are created for the ``restarted'' MzScheme. (The new namespace is installed as the current namespace in the new thread.) In the new thread, restarting performs the following actions:

• The init-namespace procedure is called with no arguments. The return value is ignored.

• Expressions and files specified by argv are evaluated and loaded. If an error occurs, the remaining expressions and files are ignored, and the return value for restart-mzscheme is set to #f.

• The read-eval-print-loop procedure is called, unless a flag in init-argv or argv disables it. When read-eval-print-loop returns, the return value for restart-mzscheme is set to #t.

Before evaluating command-line arguments, an exit handler is installed that immediately returns from restart-mzscheme with the value supplied to the handler. This exit handler remains in effect when read-eval-print-loop is called (unless a command-line argument changes it). If restart-mzscheme returns normally, the return value is determined as described above. (Note that an error in a command-line expression followed by read-eval-print-loop produces a #t result. This is consistent with MzScheme's stand-alone behavior.)