gosh is invoked without any script files,
it goes into interactive read-eval-print loop (REPL).
To exit the interpreter, type EOF (usually Control-D in Unix terminals)
In the interactive session,
module (see Interactive session) for the
convenience. The module also loads a file .gaucherc under
the user’s home directory if it exists.
You may put settings there that would help interactive debugging.
(As of Gauche release 0.7.3,
.gaucherc is no longer loaded when
gosh is run
in script mode.)
Note that .gaucherc is always loaded in the
gosh is invoked with
-r7 option. The file
itself is a Gauche-specific feature, so you don’t need to consider
portability in it.
I recommend you to run
gosh inside Emacs, for it has
rich features useful to interact with internal Scheme process.
Put the following line to your .emacs file:
(setq scheme-program-name "gosh -i")
And you can run
gosh by M-x run-scheme.
If you want to use multibyte characters in the interaction,
make sure your terminal’s settings is in sync with
internal character encodings.
|• Working in REPL:|
When you enter REPL, Gauche prompts you to enter a Scheme expression:
After you complete a Scheme expression and type ENTER, the result of evaluation is printed.
gosh> (+ 1 2) 3 gosh>
The REPL session binds the last three results of evaluation
in the global variables
You can use the previous results via those history variables
in subsequent expressions.
gosh> *1 3 gosh> (+ *2 3) 6
If the Scheme expression yields multiple values (see Multiple values), they are printed one by one.
gosh> (min&max 1 -1 8 3) -1 8 gosh>
The history variable
binds the first value. A list of all values are bound to
gosh> *1 -1 gosh> *2+ (-1 8)
(Note that, when you evaluate
*1 in the above example, the
history is shifted—so you need to use
*2+ to refer to the
(min&max 1 -1 8 3).)
*history procedure shows the value of history variables:
gosh> (*history) *1: (-1 8) *2: -1 *3: -1 gosh>
As a special case, if an evaluation yields zero values, history
isn’t updated. The
*history procedure returns
no values, so merely looking at the history won’t change the history
gosh> (*history) *1: (-1 8) *2: -1 *3: -1 gosh> (values) gosh> (*history) *1: (-1 8) *2: -1 *3: -1
Finally, a global variable
*e is bound to the last uncaught
error condition object.
gosh> (filter odd? ’(1 2 x 4 5)) *** ERROR: integer required, but got x Stack Trace: _______________________________________ 0 (eval expr env) At line 173 of "/usr/share/gauche-0.9/0.9.3.3/lib/gauche/interactive.scm" gosh> *e #<error "integer required, but got x">
(The error stack trace may differ depending on your installation.)
In REPL prompt, you can also enter special top-level commands for common tasks. Top-level commands are not Scheme expressions, not even S-expressions. They work like traditional line-oriented shell commands instead.
Top-level commands are prefixed by comma to be distinguished from
ordinary Scheme expressions. To see what commands are available,
,help and return.
gosh> ,help You're in REPL (read-eval-print-loop) of Gauche shell. Type a Scheme expression to evaluate. A word preceeded with comma has special meaning. Type ,help <cmd> to see the detailed help for <cmd>. Commands can be abbreviated as far as it is not ambiguous. ,a|apropos Show the names of global bindings that match the regexp. ,cd Change the current directory. ,doc|info Show info document for an entry of NAME. ,d|describe Describe the object. ,history Show REPL history. ,h|help Show the help message of the command. ,pwd Print working directory. ,source Show source code of the procedure if it's available.
To see the help of each individual commands, give the command name
(without comma) to the
gosh> ,help d Usage: d|describe [object] Describe the object. Without arguments, describe the last REPL result.
,describe) top-level command describes
the given Scheme object
or the last result if no object is given. Let’s try some:
gosh> (sys-stat "/home") #<<sys-stat> 0x2d6adc0> gosh> ,d #<<sys-stat> 0x2d6adc0> is an instance of class <sys-stat> slots: type : directory perm : 493 mode : 16877 ino : 2 dev : 2081 rdev : 0 nlink : 9 uid : 0 gid : 0 size : 208 atime : 1459468837 mtime : 1401239524 ctime : 1401239524
In the above example, first we evaluated
<sys-stat> object. The subsequent
command describes the returned
The description depends on the type of objects. Some types of objects shows extra information. If you describe an exact integer, it shows alternative interpretations of the number:
gosh> ,d 1401239524 1401239524 is an instance of class <integer> (#x538537e4, ~ 1.3Gi, 2014-05-28T01:12:04Z as unix-time) gosh> ,d 48 48 is an instance of class <integer> (#x30, #\0 as char, 1970-01-01T00:00:48Z as unix-time)
If you describe a symbol, its known bindings is shown.
gosh> ,d 'filter filter is an instance of class <symbol> Known bindings for variable filter: In module `gauche': #<closure (filter pred lis)> In module `gauche.collection': #<generic filter (2)>
If you describe a procedure, and its source code location is known,
that is also shown (see the
Defined at... line):
gosh> ,d string-interpolate #<closure (string-interpolate str :optional (legacy? #f))> is an instance of class <procedure> Defined at "../lib/gauche/interpolate.scm":64 slots: required : 1 optional : #t optcount : 1 locked : #f currying : #f constant : #f info : (string-interpolate str :optional (legacy? #f)) setter : #f
Let’s see a couple of other top-level commands. The
command shows the manual entry of the given procedure, variable, syntax,
module or a class. (The text is searched from the installed
info document of Gauche. If you get an error, check if the
info document is properly installed.)
gosh> ,info append -- Function: append list ... [R7RS] Returns a list consisting of the elements of the first LIST followed by the elements of the other lists. The resulting list is always newly allocated, except that it shares structure with the last list argument. The last argument may actually be any object; an improper list results if the last argument is not a proper list. gosh> ,info srfi-19 -- Module: srfi-19 This SRFI defines various representations of time and date, and conversion methods among them. On Gauche, time object is supported natively by '<time>' class (*note Time::). Date object is supported by '<date>' class described below. gosh> ,info <list> -- Builtin Class: <list> An abstract class represents lists. A parent class of '<null>' and '<pair>'. Inherits '<sequence>'. Note that a circular list is also an instance of the '<list>' class, while 'list?' returns false on the circular lists and dotted lists. (use srfi-1) (list? (circular-list 1 2)) => #f (is-a? (circular-list 1 2) <list>) => #t
,a command (or
,apropos) shows the global identifiers
matches the given name or regexp:
gosh> ,a filter filter (gauche) filter! (gauche) filter$ (gauche) filter-map (gauche)
apropos command only shows the symbols that has
loaded into the current process. On the other hand, the
command searches info document, regardless of the named entity
has loaded into the current process or not.
Note: If you invoke
-q option, which tells
gosh not to load the initialization files, you still get
a REPL prompt but no fancy features such as history variables
are available. Those convenience features are implemented in
gauche.interactive module, which isn’t loaded with