basic.1

比较早的一款BASIC解释器 可作为学习BASIC解释器的一个参考

Returns a substring of a$ starting at the i'th
positions and j characters in length. If the second
parameter is not specified then the substring is
taken from the start position to the end of a$.

.TP
.B right$(a$, EXPR )

Returns the right EXPR characters of a$.

.TP
.B left$(a$, EXPR )

Returns the left EXPR characters of a$.

.TP
.B field$( STRINGVAL, VAL { , STRINGVAL } )

Returns the N-th field of the first string.  If the
optional string is present then use the first character
of that string as the field separator.  The default
separator is a space.  Similar to UNIX 'awk' fields.

e.g.  field$("1 22 333 4", 3)  returns  "333"

If VAL is -1 then returns a string with a length
equal to the number of seperators in the first string.

.TP
.B hex$( VAL { , EXPR } )
.TP
.B bin$( VAL { , EXPR } )

Returns the hexadecimal or binary string representation
corresponding to VAL.  If EXPR is present then the
string is padded with zeros to make it that length.

.TP
.B lcase$( STRINGVAL )

Returns STRINGVAL in all lower case characters.

.TP
.B errorstatus$

Returns the error message for the last error.
.PP
.SH OPERATORS
.PP

.TP
.B Math Operators
The following math operators  are available:
        ^       exponentiation
        *       multiplication
        /       division
        mod     remainder
        +       addition
        -       subtraction

.TP
.B Logical Operators
Any non-zero value is true.
Logical Operators:
        not     logical not

.TP
.B Bitwise Operators
Bitwise Operators:
        and     bitwise and
        or      bitwise or
        xor     bitwise exclusive-or

.TP
.B Comparison Operators
Arithmetic Comparison Operators:
        <=      less than or equal
        <>      not equal to
        >=      greater than or equal
        =       equal
        >       greater than
        <       less than

.TP
.B x$=y$, x$y$, x$<=y$, x$>=y$, x$<>y$

String comparisons; result is 1 if true, 0 if false.

.TP
.B Operator Precedence
Operator Precedence (highest to lowest):
        ( )
        functions()
        ^
        - {unary_minus}
        * / mod
        + -
        = < > <= >= <>
        not
        and
        or xor
.PP

.SH UNIX commands:
.PP

.TP
.B gotoxy VAL, VAL

Sets the horizontal and vertical location of the text
output cursor using vt100/xterm control characters.
(0,0) is the upper left corner.

.TP
.B open STRINGEXPR for input as # FNUM
Where STRINGEXPR start with the string: "pipe:"

Opens an input pipe with STRINGEXPR as the input
process command string.

Example:
        open "pipe:/bin/ls -l" for input as #1
.PP

.TP
.B open STRINGEXPR , INTEXPR for input as # FNUM
.B open STRINGEXPR , INTEXPR for output as # FNUM
Where STRINGEXPR start with the string: "socket:"

Opens a socket with STRINGEXPR as the hostname and INTEXPR as the
port number.  The input needs to be opened before the output.

Example:
        open "socket:foo.net",7 for input as #3
        : rem echo port
        open "socket:foo.net",7 for output as #4
        print #4, "hello"
        input #3, a$
        close #4 : close #3

.PP

.SH UNIX/linux functions:
.PP

.TP
.B #cbas#run_only

When used in a Basic program file, upon load, sets 
the Chipmunk Basic interpreter to run-only mode,
interactive mode disabled.  The Stop and End
commands and the use of Ctrl-C will quit the
interpreter.

.TP
.B sys( STRINGVAL )

UNIX system call.  The string parameter is given to
the shell as a command.  Returns exit status.

.TP
.B fn kill( STRINGVAL )

Removes the file with filename STRINGVAL.  Returns 0
on success.

.TP
.B getenv$( STRINGVAL )
 
Returns value for environment name STRINGVAL.
      
.TP
.B argv$
Returns the UNIX shell command line arguments.
.PP
.SH Macintosh commands:
.PP

*** NOTE ***
.PP

Many MacOS specific functions and commands are only
documented in the Chipmunk Basic quick reference file.

.TP
.B gotoxy VAL, VAL

Set the horizontal and vertical location of the
text output cursor.  (0,0) is the upper left corner.

.TP
.B moveto VAL, VAL

Sets the (x,y) location of the graphics pen.

.TP
.B lineto VAL, VAL

Draws a line from the current pen location to location
(x,y) in the graphics window.

.TP
.B window x, y, char_cols, char_lines

Change the text console window position and size.

.TP
.B morse STRINGVAL { , VAL, VAL, VAL, VAL }

Plays morse code through the speaker.
The parameters are: dot-speed-wpm, volume{0..100},
word-speed-wpm, frequency{in Hz or cps}

.TP
.B sound VAL, VAL, VAL 

The parameters are:
frequency{in Hz}, seconds_duration, volume{0..100}

.TP
.B say STRINGVAL

Speaks STRINGVAL if the Speech Manager Extension is
resident.  Try "say a$,200,46,1" for faster speech.

.TP
.B open "SFGetFile" for input  as #FNUM
.TP
.B open "SFPutFile" for output as #FNUM

Puts up a standard file dialog for the file name.

.TP
.B files { STRINGVAL }

Displays a listing of files in the named or current
directory.

.SH Macintosh functions:
.PP

.TP
.B fre
Returns the amount of memory left for program use. 

.TP
.B date$
Returns a string corresponding to the current date.

.TP
.B time$
Returns a string corresponding to the current time.

.TP
.B pos(VAL)

Returns the horizontal position of the text cursor.
If VAL is negative returns the vertical position.

.TP
.B errorstatus$

Also returns the full path name of the program and
files opened by SFGetFile and SFPutFile. (Only under System 7
and also only if the name fits in a string variable)


.SH Macintosh menu items:
.PP

.TP
.B Open 
or 
.B cmd-O

will put up a dialog to allow selection
of a program file to load.  Basic Program
file names must end with a ".bas" suffix.

.TP
.B Copy
will allow copying picts from the graphics
window.

.TP .
Command-period will stop program execution.

.TP
.B Print

Print graphics window if it's the frontmost
window. Only the graphics window can be printed.
.PP
.SH RESERVED WORDS AND SYMBOLS
.PP

+ - * / ^ mod  and or xor not  > < >= <= <> = ()
sqr log exp sin cos tan atn  pi
abs sgn int rnd peek val asc len
mid$ right$ left$ str$ chr$  lcase$ ucase$
goto  if then else endif  gosub return
for to step next  while wend  select case
rem  let  dim erase  data read restore   field$
input print open for output append as close# load save
random lof loc get put   
inkey$  input$ eof  files  fgetbyte# fseek# fputbyte
run stop end exit quit cont  renum  new clear
date$ time$ timer  sound morse say  doevents
home cls gotoxy htab vtab pos 
graphics sprite pset moveto lineto window scrn mouse
varptr peek poke fre push pop  isarray
sub call usr  def fn
type class extends  string integer single double
asin acos sinh cosh tanh log10 floor true false ubound
eqv imp  static  option degrees radians redim
msgbox  do loop until break
method private public local   menu dialog memstat()
draw play  bload bsave  min max mat
each  resume  function
key is each set width swap


.SH CONVENTIONS
.PP

.TP
.B EXPR            an expression that evaluates to a numeric value.
.TP
.B STRINGEXPR      a string expression.
.TP
.B VAR             a numeric variable.
.TP
.B STRINGVAR       a string variable. Name must end with a "$".
.TP
.B INTEGERVAR      a 16-bit variable. Name must end with a "%".

All program lines must begin with a line number.
Using spaces (indentation) between the line number and
program statements is legal.  Line numbers can be
between 1 and 2147483647.  Programs lines must be no
longer than 254 characters in length.

Subroutine names starting with "fn" are reserved for the
(obsolete) def fn functions.

Hexadecimal numbers can be entered by preceding them with
a "0x" as in 0x02ae, or by "&h" as in &h0172.

Multiple statements may be given on one line, separated by
colons:

10 INPUT X : PRINT X : STOP
.PP
.SH DIAGNOSTICS

Some errors can be caught by the user program using the
"on error goto" command. If no error trapping routine has been
supplied then program execution is terminated and a message is
printed with the corresponding line number.

Graphics (MacOS) may require that the preferred memory
requirements be increased using the Finder "Get Info" dialog
box.
.PP
.SH CHANGES

  v3.6.1    - changed exponentiation/negation precedence
            - changed default mat origin
  v3.6.0    - added atn(x,y), exit() status, fn kill file.
  v3.5.8b5  - changed int() to round toward negative infinity.
  
  v3.5.7b3  - added network socket i/o
  v3.5.7b2  - fixed rnd() function
  v3.5.7b1  - fixed a problem with array indexes > 65k
  v3.5.3    - allow integer (i%) variables as for/next loop indices
  v3.4.7    - lowered precedence of NOT operator
            - disabled ON GOTO range checking
  v3.4.6    - added MAT matrix statements
  v3.4.0    - OPEN ELSE added
  v3.3.4    - changed integer conversion to rounding
            - changed sub return values to: sub_name = x
            - added reserved words for: true false
  v3.3.3    - added acos, tanh, log10
  v3.2.8    - added class definitions

Many others ...

.SH BUGS
.PP

Many.  Perhaps competitive with Central American rain forests.

FOR/NEXT loops with integer indices require a variable in the
NEXT statement. Integer arrays can only have a dimension of
one and will only work in assignment (LET) statements.  All
arithmetic on integer variables is done using floating point
arithmetic.  DIM AS DOUBLE and DIM AS INTEGER statements are
ignored.

Many string functions (except +, MID$, LEN and INSTR) silently
truncate their results to 254 characters (e.g. without
warning). All string function may silently truncate strings
longer than 32766 characters. Any operation on strings longer
than 254 characters will cause the program to run slower.

Comments starting with ' sometimes can't be used after
statements that can end with a string parameter. ( : '
should always work.)

Any variables used as a CLASS, or TYPE, globally overide all
local variables of the same names.  Local TYPE'd variables
must be declared globally as TYPE'd variables.  Named SUBroutines
are slower than GOSUBs. The combined length of a SUBroutine name
and any local variables declared STATIC must be less than 29
characters.

Can't CONTinue from an error inside a named SUB subroutine.

The PRINT USING format string doesn't recognize comma's,
underscores and many other common format characters.

Macintosh screen editing will only recognise the last line
modified before a RETURN or ENTER key.  The EDIT command and
Mac screen editing are incompatible.

There are many undocumented graphics and sprite commands
and keywords in the Macintosh port.  See the accompanying
README and Chipmunk Basic quick-reference file.


.SH DISCLAIMER
.PP

There is no warranty that this document is accurate.

.SH SEE ALSO
The Chipmunk Basic Home Page:
.TP
  <http://www.nicholson.com/rhn/basic.html >


.SH AUTHORS

David Gillespie wrote basic.p 1.0 and the p2c lib.
Ron Nicholson ([e-mail]) added file i/o, graphics
and did the Unix, Macintosh and PowerMac port. (1990Aug-2002Jan)
David Forrest ([e-mail]) converted man page to nroff (1999 March)

Portions of this document are Copyright (C) 1989 Dave Gillespie.
Portions of this document are
Copyright (C)1994,2002 Ronald H. Nicholson, Jr.  All rights reserved.
"Applesoft" is a trademark of Apple Computer, Inc., etc.