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The multiple-value feature was added in R5RS.
- Function: values object ...
-
Delivers all of its arguments to its continuation.
- Function: call-with-values thunk receiver
-
Call its thunk argument with a continuation that,
when passed some values, calls the receiver procedure
with those values as arguments.
- Constant: #!optional
-
Special self-evaluating literal used in lambda parameter lists
before optional parameters.
- Constant: #!rest
-
Special self-evaluating literal used in lambda parameter lists
before the rest parameter.
- Constant: #!key
-
Special self-evaluating literal used in lambda parameter lists
before keyword parameters.
- Constant: #!eof
-
The end-of-file object.
Note that if the Scheme reader sees this literal at top-level,
it is returned literally. This is indistinguishable from
coming to the end of the input file. If you do not want to end reading,
but want the actual value of #!eof
, you should quote it.
- Constant: #!void
-
The void value. Same as
(values)
.
If this is the value of an expression in a read-eval-print loop,
nothing is printed.
- Constant: #!null
-
The Java
null
value. This is not really a Scheme value,
but is useful when interfacing to low-level Java code.
Keywords are similar to symbols. The main difference is that keywords are
self-evaluating and therefore do not need to be quoted in expressions.
They are used mainly for specifying keyword arguments.
keyword = identifier:
An alternative syntax, with the colon first, is supported for
compatibility with Common Lisp and some other Scheme implementations:
keyword = :identifier
Putting the colon first has exactly the same effect as putting it last;
putting is last is recommended, and is how keywords are printed.
A keyword is a single token; therefore no whitespace is allowed between
the identifier and the colon (which is not considered part
of the name of the keyword).
- Function: keyword? obj
-
Return
#t
if obj is a keyword, and otherwise returns #f
.
- Function: keyword->string keyword
-
Returns the name of keyword as a string.
The name does not include the final
#\:
.
- Function: string->keyword string
-
Returns the keyword whose name is string.
(The string does not include a final
#\:
.)
The formal arguments list of a lambda expression has two
extendsions over standard Scheme:
Kawa borrows the extended formal argument list of DSSSL,
and Kawa allows you to declare the type of the parameter.
lambda-expression = (lambda formals [rtype] body)
where
formals = (formal-arguments) | rest-arg
You can of course also use the extended format in a define
:
(define (name formal-arguments) [rtype] body)
formal-arguments =
req-opt-args (rest-key-args | . rest-arg)
req-opt-args = req-arg ... [#!optional opt-arg ...]
rest-key-args = [#!rest rest-arg] [#key key-arg ...]
req-arg = variable [:: type] | (variable type)
opt-arg = arg-with-default
key-arg = arg-with-default
arg-with-default = variable [:: type] | (variable initializer [type]) | (variable :: type [initializer])
rest-arg = variable
When the procedure is applied to a list of actual arguments, the formal and
actual arguments are processed from left to right as follows:
-
The req-args are bound to actual arguments starting with the
first actual argument. It shall be an error if there are fewer actual
arguments then there are req-args.
-
Next the opt-args are bound to remaining actual arguemnts.
If there are fewer remaining actual arguments than there are
opt-args, then the remaining variables are bound
to the corresponding initializer, if one was specified, and
otherwise to
#f
. The initializer is evaluated in an
environment in which all the previous formal parameters have been bound.
-
If there is a rest-arg, it is bound to a list of all the
remaining actual arguments. These remaining actual arguments are also
eligible to be bound to keyword arguments. If there is no
rest-arg and there are no key-args, then it shall
be an error if there are any remaining actual arguments.
-
If
#!key
was specified, then there shall be an even number of
remaining actual arguments. These are interpreted as a series of pairs,
where the first member of each pair is a keyword specifying the argument name,
and the second is the corresponding value. It shall be an error if the first
member of a pair is not a keyword. It shall be an error if the argument name
is not the same as a variable in a key-args, unless there
is a rest-arg. If the same argument name occurs more than once
in the list of actual arguments, then the first value is used.
If there is no actual argument for a particular key-arg,
then the variable is bound
to the corresponding initializer, if one was specified, and
otherwise to #f
. The initializer is evaluated in an
environment in which all the previous formal parameters have been bound.
If a type is specified, the corresponding actual argument (or
the initializer default value) is coerced to the specified type.
In the function body, the parameter has the specified type.
If rtype (the first form of the function body) is an unbound
identifier of the form <TYPE>
(that is the first character
is `<' and the last is `>'), then tha specifies the
functions return type. It is syntactic sugar for
(as <TYPE> (begin BODY))
.
As a super-class of numbers, Kawa also provides quantities.
A quantity is a product of a unit and a pure number.
The number part can be an arbitrary complex number.
The unit is a product of integer powers of base units,
such as meter or second.
Kawa quantities are a generalization of the quantities in DSSSL,
which only has length-derived quantities.
The precise syntax of quantity literals may change,
but some examples are 10pt
(10 points), 5s
(5 seconds),
and 4cm2
(4 square centimeters).
- Function: quantity? object
-
True iff object is a quantity. Note that all numbers are
quantities, but not the other way round.
Currently, there are no quantities that re not numbers.
To distinguish a plain unit-less number from a quantity,
you can use
complex?
.
- Function: quantity->number q
-
Returns the pure number part of the quantity q, relative to
primitive (base) units.
If q is a number, returns q.
If q is a unit, yields the magitude of q relative to base units.
- Function: quantity->unit q
-
Returns the unit of the quantity q.
If q is a number, returns the empty unit.
- Function: make-quantity x unit
-
Returns the product of x (a pure number) and unit.
You can specify a string instead of unit, such as
"cm"
or "s"
(seconds).
- Syntax: define-unit unit-name expression
-
Define unit-name as a unit (that can be used in literals)
equal to the quantity expression.
These functions operate on the 2's complement binary representation
of an exact integer.
- Function: logand i ...
-
Returns the bit-wise logical "and" of the arguments.
If no argument is given, the result is -1.
- Function: logior i ...
-
Returns the bit-wise logical "(inclusive) or" of the arguments.
If no argument is given, the result is 0.
- Function: logxor i ...
-
Returns the bit-wise logical "exclusive or" of the arguments.
If no argument is given, the result is 0.
- Function: lognot i
-
Returns the bit-wise logical inverse of the argument.
- Function: logop op x y
-
Perform one of the 16 bitwise operations of x and y,
depending on op.
- Function: bittest i j
-
Returns true if the arguments have any bits in common.
Same as
(not (zero? (logand i j)))
,
but is more efficient.
- Function: logbit? i pos
-
Returns
#t
iff the bit numbered pos in i is one.
- Function: arithmetic-shift i j
-
Shifts i by j.
It is a "left" shift if
j>0
, and
a "right" shift if j<0
.
The result is equal to (floor (* i (expt 2 j)))
.
- Function: ash i j
-
Alias for
arithmetic-shift
.
- Function: logcount i
-
Count the number of 1-bits in i, if it is non-negative.
If i is negative, count number of 0-bits.
- Function: integer-length i
-
Return number of bits needed to represent i in an unsigned field.
Regardless of the sign of i, return one less than the number of bits
needed for a field that can represent i as a two's complement integer.
- Function: bit-extract n start end
-
Return the integer formed from the (unsigned) bit-field
starting at start and ending just before end.
Same as
(arithmetic-shift (bitand n (bitnot (arithmetic-shift -1 end))) (- start))
.
- Function: string-upcase str
-
Return a new string where the letters in str are replaced
by their upper-case equivalents.
- Function: string-downcase str
-
Return a new string where the letters in str are replaced
by their lower-case equivalents.
- Function: string-capitalize str
-
Return a new string where the letters in str that start a new word
are replaced by their title-case equivalents, while non-initial letters
are replaced by their lower-case equivalents.
- Function: string-upcase! str
-
Destructively modify str, replacing the letters
by their upper-case equivalents.
- Function: string-downcase! str
-
Destructively modify str, replacing the letters
by their upper-lower equivalents.
- Function: string-capitalize! str
-
Destructively modify str, such that the letters that start a new word
are replaced by their title-case equivalents, while non-initial letters
are replaced by their lower-case equivalents.
Uniform vectors are vectors whose elements are of the same numeric type.
The are defined by SRFI-4.
However, the type names (such as <s8vector>
) are a Kawa extension.
- Variable: <s8vector>
-
The type of uniform vectors where each element can contain
a signed 8-bit integer. Represented using an array of
<byte>
.
- Variable: <u8vector>
-
The type of uniform vectors where each element can contain
an unsigned 8-bit integer. Represented using an array of
<byte>
,
but each element is treated as if unsigned.
- Variable: <s16vector>
-
The type of uniform vectors where each element can contain
a signed 16-bit integer. Represented using an array of
<short>
.
- Variable: <u16vector>
-
The type of uniform vectors where each element can contain
an unsigned 16-bit integer. Represented using an array of
<short>
,
but each element is treated as if unsigned.
- Variable: <s32vector>
-
The type of uniform vectors where each element can contain
a signed 32-bit integer. Represented using an array of
<int>
.
- Variable: <u32vector>
-
The type of uniform vectors where each element can contain
an unsigned 32-bit integer. Represented using an array of
<int>
,
but each element is treated as if unsigned.
- Variable: <s64vector>
-
The type of uniform vectors where each element can contain
a signed 64-bit integer. Represented using an array of
<long>
.
- Variable: <u64vector>
-
The type of uniform vectors where each element can contain
an unsigned 64-bit integer. Represented using an array of
<long>
,
but each element is treated as if unsigned.
- Variable: <f32vector>
-
The type of uniform vectors where each element can contain
a 32-bit floating-point real. Represented using an array of
<float>
.
- Variable: <f64vector>
-
The type of uniform vectors where each element can contain
a 64-bit floating-point real. Represented using an array of
<double>
.
- Function: s8vector? value
-
- Function: u8vector? value
-
- Function: s16vector? value
-
- Function: u16vector? value
-
- Function: s32vector? value
-
- Function: u32vector? value
-
- Function: s64vector? value
-
- Function: u64vector? value
-
- Function: f32vector? value
-
- Function: f64vector? value
-
Return true iff value is a uniform vector of the specified type.
- Function: make-s8vector n [value]
-
- Function: make-u8vector n [value]
-
- Function: make-s16vector n [value]
-
- Function: make-u16vector n [value]
-
- Function: make-s32vector n [value]
-
- Function: make-u32vector n [value]
-
- Function: make-s64vector n [value]
-
- Function: make-u64vector n [value]
-
- Function: make-f32vector n [value]
-
- Function: make-f64vector n [value]
-
Create a new uniform vector of the specified type,
having room for n elements.
Initialize each element to value if it is specified; zero otherwise.
- Function: s8vector value ...
-
- Function: u8vector value ...
-
- Function: s16vector value ..
-
- Function: u16vector value ...
-
- Function: s32vector value ...
-
- Function: u32vector value ...
-
- Function: s64vector value ...
-
- Function: u64vector value ...
-
- Function: f32vector value ...
-
- Function: f64vector value ...
-
Create a new uniform vector of the specified type,
whose length is the number of values specified,
and initialize it using those values.
- Function: s8vector-length v
-
- Function: u8vector-length v
-
- Function: s16vector-length v
-
- Function: u16vector-length v
-
- Function: s32vector-length v
-
- Function: u32vector-length v
-
- Function: s64vector-length v
-
- Function: u64vector-length v
-
- Function: f32vector-length v
-
- Function: f64vector-length v
-
Return the length (in number of elements) of the uniform vector v.
- Function: s8vector-ref v i
-
- Function: u8vector-ref v i
-
- Function: s16vector-ref v i
-
- Function: u16vector-ref v i
-
- Function: s32vector-ref v i
-
- Function: u32vector-ref v i
-
- Function: s64vector-ref v i
-
- Function: u64vector-ref v i
-
- Function: f32vector-ref v i
-
- Function: f64vector-ref v i
-
Return the element at index i of the uniform vector v.
- Function: s8vector-set! v i x
-
- Function: u8vector-set! v i x
-
- Function: s16vector-set! v i x
-
- Function: u16vector-set! v i x
-
- Function: s32vector-set! v i x
-
- Function: u32vector-set! v i x
-
- Function: s64vector-set! v i x
-
- Function: u64vector-set! v i x
-
- Function: f32vector-set! v i x
-
- Function: f64vector-set! v i x
-
Set the element at index i of uniform vector v
to the value x, which must be a number coercible
to the appropriate type.
- Function: s8vector->list v
-
- Function: u8vector->list v
-
- Function: s16vector->list v
-
- Function: u16vector->list v
-
- Function: s32vector->list v
-
- Function: u32vector->list v
-
- Function: s64vector->list v
-
- Function: u64vector->list v
-
- Function: f32vector->list v
-
- Function: f64vector->list v
-
Convert the uniform vetor v to a list containing the elments of v.
- Function: list->s8vector l
-
- Function: list->u8vector l
-
- Function: list->s16vector l
-
- Function: list->u16vector l
-
- Function: list->s32vector l
-
- Function: list->u32vector l
-
- Function: list->s64vector l
-
- Function: list->u64vector l
-
- Function: list->f32vector l
-
- Function: list->f64vector l
-
Create a uniform vector of the appropriate type, initializing it
with the elements of the list l. The elements of l
must be numbers coercible the new vector's element type.
- Function: file-exists? filename
-
Returns true iff the file named filename actually exists.
- Function: file-directory? filename
-
Returns true iff the file named filename actually exists
and is a directory.
- Function: file-readable? filename
-
Returns true iff the file named filename actually exists
and can be read from.
- Function: file-writable? filename
-
Returns true iff the file named filename actually exists
and can be writen to.
(Undefined if the filename does not exist,
but the file can be created in the directory.)
- Function: delete-file filename
-
Delete the file named filename.
- Function: rename-file oldname newname
-
Renames the file named oldname to newname.
- Function: copy-file oldname newname-from path-to
-
Copy the file named oldname to newname.
The return value is unspecified.
- Function: create-directory dirname
-
Create a new directory named dirname.
Unspecified what happens on error (such as exiting file with the same name).
(Currently returns
#f
on error, but may change to be more compatible
with scsh.)
- Function: system-tmpdir
-
Return the name of the default directory for temporary files.
- Function: make-temporary-file [format]
-
Return a file with a name that does not match any existing file.
Use format (which defaults to
"kawa~d.tmp"
) to generate
a unique filename in (system-tmpdir)
.
The current implementation is not safe from race conditions;
this will be fixed in a future release (using Java2 features).
- Function: read-line [port [handle-newline]]
-
Reads a line of input from port.
The handle-newline parameter determines what is done with
terminating end-of-line delimiter.
The default,
'trim
, ignores the delimiter;
'peek
leaves the delimiter in the input stream;
'concat
appends the delimiter to the returned value;
and 'split
returns the delimiter as a second value.
You can use the last three options to tell if the string was
terminated by end-or-line or by end-of-file.
- Function: open-input-string string
-
Takes a string and returns an input port that delivers characters
from the string. The port can be closed by
close-input-port
,
though its storage will be reclaimed by the
garbage collector if it becomes inaccessible.
(define p
(open-input-string "(a . (b c . ())) 34"))
(input-port? p) --> #t
(read p) --> (a b c)
(read p) --> 34
(eof-object? (peek-char p)) --> #t
- Function: open-output-string
-
Returns an output port that will accumulate characters
for retrieval by
get-output-string
.
The port can be closed by the procedure close-output-port
,
though its storage will be reclaimed by the garbage collector
if it becomes inaccessible.
(let ((q (open-output-string))
(x '(a b c)))
(write (car x) q)
(write (cdr x) q)
(get-output-string q)) --> "a(b c)"
- Function: get-output-string output-port
-
Given an output port created by
open-output-string
,
returns a string consisting of the characters that have been
output to the port so far.
- Function: call-with-input-string string proc
-
Create an input port that gets its data from string,
call proc with that port as its one argument, and return
the result from the call of proc
- Function: call-with-output-string proc
-
Create an output port that writes its data to a string,
and call proc with that port as its one argument.
Return a string consisting of the data written to the port.
- Function: force-output [port]
-
Forces any pending output on port to be delivered to the output
device and returns an unspecified value. If the port argument is
omitted it defaults to the value returned by
(current-output-port)
.
An interactive input port has a prompt procedure associated with it.
The prompt procedure is called before a new line is read. It is passed
the port as an argument, and returns a string, which gets printed as a prompt.
- Function: input-port-prompter port
-
Get the prompt procedure associated with port.
- Function: set-input-port-prompter! port prompter
-
Set the prompt procedure associated with port to prompter,
which must be a one-argument procedure taking an input port,
and returning a string.
- Function: default-prompter port
-
The default prompt procedure. It returns
"#|kawa:L|# "
, where
L is the current line number of port.
When reading a continuation line, the result
is "#|C---:L|# "
, where C
is the character returned
by (input-port-read-state port)
.
The prompt has the form of a comment to make it easier to cut-and-paste.
- Function: port-column input-port
-
- Function: port-line input-port
-
Return the current column number or line number of input-port,
using the current input port if none is specified.
If the number is unknown, the result is
#f
. Otherwise,
the result is a 0-origin integer - i.e. the first character
of the first line is line 0, column 0. (However, when you
display a file position, for example in an error message,
we recommend you add 1 to get 1-origin integers. This is
because lines and column numbers traditionally start with
1, and that is what non-programmers will find most natural.)
- Function: set-port-line! port line
-
Set (0-origin) line number of the current line of port to num.
- Function: input-port-line-number port
-
Get the line number of the current line of port,
which must be a (non-binary) input port.
The initial line is line 1.
Deprecated; replaced by
(+ 1 (port-line port))
.
- Function: set-input-port-line-number! port num
-
Set line number of the current line of port to num.
Deprecated; replaced by
(set-port-line port (- num 1))
.
- Function: input-port-column-number port
-
Get the column number of the current line of port,
which must be a (non-binary) input port.
The initial column is column 1.
Deprecated; replaced by
(+ 1 (port-column port))
.
- Function: input-port-read-state port
-
Returns a character indicating the current
read
state of the port.
Returns #\Return
if not current doing a read,
#\"
if reading a string; #\|
if reading a comment; #\(
if inside a list; and #\Space
when otherwise in a read
.
The result is intended for use by prompt prcedures, and is not necessarily
correct except when reading a new-line.
- Variable: symbol-read-case
-
A symbol that controls how
read
handles letters when reading a symbol.
If the first letter is `U', then letters in symbols are upper-cased.
If the first letter is `D' or `L', then letters
in symbols are down-cased.
If the first letter is `I', then the case of letters in symbols
is inverted.
Otherwise (the default), the letter is not changed.
(Letters following a `\' are always unchanged.)
- Variable: port-char-encoding
-
Controls how bytes in external files are converted to/from internal
Unicode characters. Can be either a symbol or a boolean.
If
port-char-encoding
is #f
, the file is assumed
to be a binary file and no conversion is done.
Otherwise, the file is a text file. The default is #t
, which
uses a locale-dependent conversion. If port-char-encoding
is a symbol, it must be the name of a character encoding known to Java.
For all text files (that is if port-char-encoding
is not #f
),
on input a #\Return
character or
a #\Return
followed by #\Newline
are converted into plain #\Newline
.
This variable is checked when the file is opened; not when actually
reading or writing. Here is an example of how you can safely
change the encoding temporarily:
(define (open-binary-input-file name)
(fluid-let ((port-char-encoding #f)) (open-input-file name)))
- Function: format destination fmt . arguments
-
An almost complete implementation of Common LISP format description
according to the CL reference book Common LISP from Guy L.
Steele, Digital Press. Backward compatible to most of the available
Scheme format implementations.
Returns #t
, #f
or a string; has side effect of printing
according to fmt. If destination is #t
,
the output is to the current output port and #t
is returned. If
destination is #f
, a formatted string is returned as the
result of the call. If destination is a string,
destination is regarded as the format string; fmt is
then the first argument and the output is returned as a string. If
destination is a number, the output is to the current error port
if available by the implementation. Otherwise destination must be
an output port and #t
is returned.
fmt must be a string or an instance of gnu.text.MessageFormat
or java.text.MessageFormat
. If fmt is a string,
it is parsed as if by parse-format
.
- Function: parse-format format-string
-
Parses
format-string
, which is a string of the form of a Common LISP
format description. Returns an instance of gnu.text.ReportFormat
,
which can be passed to the format
function.
A format string passed to format
or parse-format
consists of format directives (that start with `~'),
and regular characters (that are written directly to the destination).
Most of the Common Lisp (and Slib) format directives are implemented.
Neither justification, nor pretty-printing are supported yet.
Plus of course, we need documentation for format
!
Documentation syntax: Uppercase characters represent the corresponding
control directive characters. Lowercase characters represent control
directive parameter descriptions.
~A
-
Any (print as
display
does).
~@A
-
left pad.
~mincol,colinc,minpad,padcharA
-
full padding.
~S
-
S-expression (print as
write
does).
~@S
-
left pad.
~mincol,colinc,minpad,padcharS
-
full padding.
~C
-
Character.
~@C
-
prints a character as the reader can understand it (i.e.
#\
prefixing).
~:C
-
prints a character as emacs does (eg.
^C
for ASCII 03).
~D
-
Decimal.
~@D
-
print number sign always.
~:D
-
print comma separated.
~mincol,padchar,commachar,commawidthD
-
padding.
~X
-
Hexadecimal.
~@X
-
print number sign always.
~:X
-
print comma separated.
~mincol,padchar,commachar,commawidthX
-
padding.
~O
-
Octal.
~@O
-
print number sign always.
~:O
-
print comma separated.
~mincol,padchar,commachar,commawidthO
-
padding.
~B
-
Binary.
~@B
-
print number sign always.
~:B
-
print comma separated.
~mincol,padchar,commachar,commawidthB
-
padding.
~nR
-
Radix n.
~n,mincol,padchar,commachar,commawidthR
-
padding.
~@R
-
print a number as a Roman numeral.
~:@R
-
print a number as an "old fashioned" Roman numeral.
~:R
-
print a number as an ordinal English number.
~:@R
-
print a number as a cardinal English number.
~P
-
Plural.
~@P
-
prints
y
and ies
.
~:P
-
as
~P but jumps 1 argument backward.
~:@P
-
as
~@P but jumps 1 argument backward.
commawidth is the number of characters between two comma characters.
~F
-
Fixed-format floating-point (prints a flonum like mmm.nnn).
~width,digits,scale,overflowchar,padcharF
-
~@F
-
If the number is positive a plus sign is printed.
~E
-
Exponential floating-point (prints a flonum like mmm.nnn
E
ee)
~width,digits,exponentdigits,scale,overflowchar,padchar,exponentcharE
-
~@E
-
If the number is positive a plus sign is printed.
~G
-
General floating-point (prints a flonum either fixed or exponential).
~width,digits,exponentdigits,scale,overflowchar,padchar,exponentcharG
-
~@G
-
If the number is positive a plus sign is printed.
A slight difference from Common Lisp: If the number is printed
in fixed form and the fraction is zero,
then a zero digit is printed for the fraction, if allowed by the width
and digits is unspecified.
~$
-
Dollars floating-point (prints a flonum in fixed with signs separated).
~digits,scale,width,padchar$
-
~@$
-
If the number is positive a plus sign is printed.
~:@$
-
A sign is always printed and appears before the padding.
~:$
-
The sign appears before the padding.
~%
-
Newline.
~n%
-
print n newlines.
~&
-
print newline if not at the beginning of the output line.
~n&
-
prints
~&
and then n-1 newlines.
~|
-
Page Separator.
~n|
-
print n page separators.
~~
-
Tilde.
~n~
-
print n tildes.
~
<newline>
-
Continuation Line.
~:
<newline>
-
newline is ignored, white space left.
~@
<newline>
-
newline is left, white space ignored.
~T
-
Tabulation.
~@T
-
relative tabulation.
~colnum,colincT
-
full tabulation.
~?
-
Indirection (expects indirect arguments as a list).
~@?
-
extracts indirect arguments from format arguments.
~(str~)
-
Case conversion (converts by
string-downcase
).
~:(str~)
-
converts by
string-capitalize
.
~@(str~)
-
converts by
string-capitalize-first
.
~:@(str~)
-
converts by
string-upcase
.
~*
-
Argument Jumping (jumps 1 argument forward).
~n*
-
jumps n arguments forward.
~:*
-
jumps 1 argument backward.
~n:*
-
jumps n arguments backward.
~@*
-
jumps to the 0th argument.
~n@*
-
jumps to the nth argument (beginning from 0)
~[str0~;str1~;...~;strn~]
-
Conditional Expression (numerical clause conditional).
~n[
-
take argument from n.
~@[
-
true test conditional.
~:[
-
if-else-then conditional.
~;
-
clause separator.
~:;
-
default clause follows.
~{str~}
-
Iteration (args come from the next argument (a list)).
~n{
-
at most n iterations.
~:{
-
args from next arg (a list of lists).
~@{
-
args from the rest of arguments.
~:@{
-
args from the rest args (lists).
~^
-
Up and out.
~n^
-
aborts if n = 0
~n,m^
-
aborts if n = m
~n,m,k^
-
aborts if n <= m <= k
~:A
-
print
#f
as an empty list (see below).
~:S
-
print
#f
as an empty list (see below).
~<~>
-
Justification.
~:^
-
These are not necesasrily implemented in Kawa!
~I
-
print a R4RS complex number as
~F~@Fi
with passed parameters for
~F
.
~Y
-
Pretty print formatting of an argument for scheme code lists.
~K
-
Same as
~?.
~!
-
Flushes the output if format destination is a port.
~_
-
Print a
#\space
character
~n_
-
print n
#\space
characters.
~nC
-
Takes n as an integer representation for a character. No arguments
are consumed. n is converted to a character by
integer->char
. n must be a positive decimal number. ~:S
-
Print out readproof. Prints out internal objects represented as
#<...>
as strings "#<...>"
so that the format output can always
be processed by read
.
~:A
-
Print out readproof. Prints out internal objects represented as
#<...>
as strings "#<...>"
so that the format output can always
be processed by read
.
~F, ~E, ~G, ~$
-
may also print number strings, i.e. passing a number as a string and
format it accordingly.
- Function: catch key thunk handler
-
Invoke thunk in the dynamic context of handler for
exceptions matching key. If thunk throws to the symbol key,
then handler is invoked this way:
(handler key args ...)
key may be a symbol. The thunk takes no
arguments. If thunk returns normally, that is the return value of
catch
.
Handler is invoked outside the scope of its own catch
. If
handler again throws to the same key, a new handler from further
up the call chain is invoked.
If the key is #t
, then a throw to any symbol will match
this call to catch
.
- Function: throw key &rest args ...
-
Invoke the catch form matching key, passing args to the
handler.
If the key is a symbol it will match catches of the same
symbol or of #t.
If there is no handler at all, an error is signaled.
- procedure: error message args ...
-
Raise an error with key
misc-error
and a message constructed by
displaying msg and writing args.
This normally prints a stack trace, and brings you back to
the top level, or exits kawa if you are not running interactively.
- Function: primitive-throw exception
-
Throws the exception, which must be an instance of a sub-class
of
<java.lang.Throwable>
.
- Syntax: try-finally body handler
-
Evaluate body, and return its result.
However, before it returns, evaluate handler.
Even if body returns abnormally (by throwing an exception),
handler is evaluated.
(This is implemented just like Java's try
-finally
.)
- Syntax: try-catch body handler ...
-
Evaluate body, in the conect of the given handler-specs.
Each handler has the form:
var type exp ...
If an exception is thrown in body, the first handle-spec
is selected such that the thrown exception is an instance of
the handler's type. If no handler is selected,
the exception is propagated through the dynamic execution context
until a matching handler is found. (If no matching handler
is found, then an error message is printed, and the computation terminated.)
Once a handler is selected,
the var is bound to the thrown exception, and the exp in
the handler are executed. The result of the try-catch
is the result of body if no exception is thrown, or the
value of the last exp in the selected handler if an
exception is thrown.
(This is implemented just like Java's try
-catch
.)
- Function: dynamic-wind in-guard thunk out-guard
-
All three arguments must be 0-argument procedures.
First calls in-guard, then thunk, then out-guard.
The result of the expression is that of thunk.
If thunk is exited abnormally (by throwing an exception or
invoking a continuation), out-guard is called.
If the continuation of the dynamic-wind is re-entered (which
is not yet possible in Kawa), the in-guard is called again.
This function was added in R5RS.
A location is a place where a value can be stored.
An lvalue is an expression that refers to a location.
(The name "lvalue" refers to the fact that the left operand
of set!
is an lvalue.)
The only kind of lvalue in standard Scheme is a variable.
Kawa also allows computed lvalues. These are procedure
calls used in "lvalue context", such as the left operand of set!
.
You can only use procedures that have an associated setter.
In that case, (set! (f arg ...) value)
is equivalent to ((setter f) value arg ...)
(It is possible the definition will change
to ((setter f) arg ... value)
if Guile goes for that.)
Currently, only a few procedures have associated setter
s,
and only builtin procedures written in Java can have setter
s.
For example:
(set! (car x) 10)
is equivalent to:
(set-car! x 10)
Kawa also gives you access to locations as first-class values:
- Syntax: location lvalue
-
Returns a location object for the given lvalue.
You can get its value (by applying it, as if it were a procedure),
and you can set its value (by using
set!
on the application).
The lvalue can be a local or global variable, or a procedure
call using a procedure that has a setter
.
(define x 100)
(define lx (location x))
(set! (lx) (cons 1 2)) ;; set x to (1 . 2)
(lx) ;; returns (1 . 2)
(define lc (location (car x)))
(set! (lc) (+ 10 (lc)))
;; x is now (11 . 2)
- Syntax: define-alias variable lvalue
-
Define variable as an alias for lvalue.
In other words, makes it so that
(location variable)
is equivalent to (location lvalue)
.
This works both top-level and inside a function.
Some people mind find it helpful to think of a location
as a settable thunk. Others may find it useful to
think of the location
syntax as similar to the C `&' operator;
for the `*' indirection operator, Kawa uses procedure application.
- Function: eval expression [environment]
-
eval
evaluates expression in the environment indicated
by environment.
The default for environment is the result
of (interaction-environment)
.
- Function: null-environment
-
This procedure returns an environment that contains no variable bindings,
but contains (syntactic) bindings for all the syntactic keywords.
The effect of assigning to a variable in this environment (such
as let
) is undefined.
- Function: scheme-report-environment version
-
The version must be an exact non-negative inetger corresponding to
a version of one of the Revisedversion Reports on Scheme.
The procedure returns an environment that contains exactly the set of
bindings specified in the corresponding report.
This implementation supports version that is 4 or 5.
The effect of assigning to a variable in this environment (such
as car
) is undefined.
- Function: interaction-environment
-
This procedure return an environment that contains implementation-defined
bindings, as well as top-level user bindings.
- Function: environment-bound? environment symbol
-
Return true
#t
if there is a binding for symbol
in environment; otherwise returns #f
.
- Syntax: fluid-let ((variable init) ...) body ...
-
Evaluate the init expressions.
Then modify the dynamic bindings for the variables to the
values of the init expressions, and evaluate the body expressions.
Return the result of the last expression in body.
Before returning, restore the original bindings.
The temporary bindings are only visible in the current thread, and its
descendent threads.
- Syntax: trace procedure
-
Cause procedure to be "traced", that is debugging output will
be written to the standard error port every time procedure
is called, with the parameters and return value.
- Syntax: untrace procedure
-
Turn off tracing (debugging output) of procedure.
There is a very preliminary interface to create parallel threads.
The interface is similar to the standard delay
/force
,
where a thread is basically the same as a promise, except that
evaluation may be in parallel.
So far, little or no effort has been made into making Kawa
thread-safe. There are no per-thread bindings, and
the current input and output parts are global.
That needs to change.
- Syntax: future expression
-
Creates a new thread that evaluates expression.
- Function: force thread
-
The standard
force
function has generalized to also work
on threads. If waits for the thread's expression to finish
executing, and returns the result.
- Function: sleep time
-
Suspends the current thread for the specified time.
The time can be either a pure number (in secords),
or a quantity whose unit is a time unit (such as
10s
).
- Function: make-process command envp
-
Creates a
<java.lang.Process>
object, using the specified
command and envp.
The command is converted to an array of Java strings
(that is an object that has type <java.lang.String[]>
.
It can be a Scheme vector or list (whose elements should be
Java strings or Scheme strings); a Java array of Java strings;
or a Scheme string. In the latter case, the command is converted
using command-parse
.
The envp is process environment; it should be either
a Java array of Java strings, or the special #!null
value.
- Function: system command
-
Runs the specified command, and waits for it to finish.
Returns the return code from the command. The return code is an integer,
where 0 conventionally means successful completion.
The command can be any of the types handled by
make-process
.
- Variable: command-parse
-
The value of this variable should be a one-argument procedure.
It is used to convert a command from a Scheme string to a Java
array of the constituent "words".
The default binding, on Unix-like systems, returns a new command to
invoke
"/bin/sh" "-c"
concatenated with the command string;
on non-Unix-systems, it is bound to tokenize-string-to-string-array
.
- Function: tokenize-string-to-string-array command
-
Uses a
java.util.StringTokenizer
to parse the command string
into an array of words. This splits the command using spaces
to delimit words; there is no special processing for quotes or other
special characters.
(This is the same as what java.lang.Runtime.exec(String)
does.)
- Function: scheme-implementation-version
-
Returns the Kawa version number as a string.
- Function: gentemp
-
Returns a new (interned) symbol each time it is called.
The symbol names are implementation-dependent.
- Syntax: defmacro name lambda-list form ...
-
Defines an old-style macro a la Common Lisp,
and installs
(lambda lambda-list form ...)
as the expansion function for name.
When the translator sees an application of name,
the expansion function is called with the rest of the application
as the actual arguments. The resulting object must be a Scheme
source form that is futher processed (it may be repeatedly macro-expanded).
If you define a macro with defmacro
, you (currently) cannot use
the macro in the same compilation as the definition.
This restriction does not apply to macros defined by define-syntax
.
- Variable: command-line-arguments
-
Any command-line arguments (following flags processed by Kawa itself)
are assigned to the global variable `command-line-arguments',
which is a vector of strings.
- Variable: home-directory
-
A string containing the home directory of the user.
- Function: exit [code]
-
Exits the Kawa interpreter, and ends the Java session.
The integer value code is returned to the operating
system. If code is not specified, zero is returned,
indicating normal (non-error) termination.
- Function: scheme-window [shared]
-
Create a read-eval-print-loop in a new top-level window.
If shared is true, it uses the same environment as the
current
(interaction-environment)
; if not (the default),
a new top-level environment is created.
You can create multiple top-level window that can co-exist.
They run in separate threads.
- Function: apply proc [arg1 ...] args
-
Args must be a sequence (list, vector, or string) or a
primitive Java array.
(This is an extension over standard Scheme, which requires that
args be a list.)
Calls the proc (which must be a procedure), using as arguments
the arg1... values plus all the elements of args.
- Syntax: constant-fold proc arg1 ...
-
Same as
(proc arg1 ...)
, unless proc and
all the following arguments are compile-time constants.
(That is: They are either constant, or symbols that have a global
binding and no lexical binding.) In that case, proc
is applied to the arguments at compile-time, and the result replaces
the constant-fold
form. If the application raises an exception,
a compile-time error is reported.
For example:
(constant-fold vector 'a 'b 'c)
is equivalent to (quote #(a b c))
, assuming vector
has not been re-bound.
- Syntax: when condition form...
-
If condition is true, evaluate each form in order,
returning the value of the last one.
- Syntax: unless condition form...
-
If condition is false, evaluate each form in order,
returning the value of the last one.
- Function: vector-append arg...
-
Creates a new vector, containing the elements from all the args
appended together. Each arg may be a vector or a list.
- Function: instance? value type
-
Returns
#t
iff value is an instance of type type.
(Undefined if type is a primitive type, such as <int>
.)
- Function: as type value
-
Converts or coerces value to a value of type type.
Throws an exception if that cannot be done.
Not supported for type to be a primitive type such as
<int>
.
- Syntax: synchronized object form ...
-
Synchronize on the given object. (This means getting an
exclusive lock on the object, by acquiring its monitor.)
Then execute the forms while holding the lock.
When the forms finish (normally or abnormally by throwing
an exception), the lock is released.
Returns the result of the last form.
Equivalent to the Java
synchronized
statement,
except that it may return a result.
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