yabasic.1

Linux下VB解释器

   clear, circle, rectangle, triangle
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Name

   clear screen - erases the text window

Synopsis

clear screen

Description

   clear screen erases the text window (the window where the output of print
   appears).

   It must be issued at least once, before some advanced screen-commands (e.g.
   print at or inkey$) may be called; this requirement is due to some
   limitations of the curses-library, which is used by yabasic under Unix for
   some commands.

Example

clear screen
print "Please press a key : ";
a$=inkey$
print a$
          

   The clear screen command is essential here; if it would be omitted, yabasic
   would issue an error ("need to call 'clear screen' first") while trying to
   execute the inkey$-function.

See also

   inkey$
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Name

   clear window - clear the graphic window and begin a new page, if printing is
   under way

Synopsis

clear window

Description

   clear window clears the graphic window. If you have started printing the
   graphic via open printer, the clear window-command starts a new page as
   well.

Example

open window 200,200
open printer "t.ps"

for a=1 to 10
if (a>1) clear window
text 100,100,"Hallo "+str$(a)
next a

close printer
close window
          

   This example prints 10 pages, with the text "Hello 1", "Hello 2", ... and so
   on. The clear screen-command clears the graphics window and starts a new
   page.

See also

   open window, open printer
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Name

   close - close a file, which has been opened before

Synopsis

close filenum
close # filenum

Description

   The close-command closes an open file. You should issue this command as soon
   as you are done with reading from or writing to a file.

Example

open "my.data" for reading as 1
input #1 a
print a
close 1
          

   This program opens the file "my.data", reads a number from it, prints this
   number and closes the file again.

See also

   open
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Name

   close curve - close a curve, that has been drawn by the line-command

Synopsis

new curve
line to x1,y1
...
close curve

Description

   The close curve-command closes a sequence of lines, that has been drawn by
   repeated line to-commands.

Example

open window 200,200
new curve
line to 100,50
line to 150,150
line to 50,150
close curve
          

   This example draws a triangle: The three line to-commands draw two lines;
   the final line is however not drawn explicitly, but drawn by the close
   curve-command.

See also

   line, new curve
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Name

   close printer - stops printing of graphics

Synopsis

close printer

Description

   The close printer-command ends the printing graphics. Between open printer
   and close printer everything you draw (e.g. circles, lines ...) is sent to
   your printer. close printer puts an end to printing and will make your
   printer eject the page.

Example

open window 200,200
open printer
circle 100,100,50
close printer
close window
          

   As soon as close printer is executed, your printer will eject a page with a
   circle on it.

See also

   open printer
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Name

   close window - close the graphics-window

Synopsis

close window

Description

   The close window-command closes the graphics-window, i.e. it makes it
   disappear from your screen. It includes an implicit close printer, if a
   printer has been opened previously.

Example

open window 200,200
circle 100,100,50
close window
          

   This example will open a window, draw a circle and close the window again;
   all this without any pause or delay, so the window will be closed before you
   may regard the circle..

See also

   open window
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Name

   color - change color for any subsequent drawing-command

Synopsis

colour red,green,blue
colour "red,green,blue"

Description

   Change the color, in which lines, dots, circles, rectangles or triangles are
   drawn. The color-command accepts three numbers in the range 0 ... 255 (as in
   the first line of the synopsis above). Those numbers specify the intensity
   for the primary colors red, green and blue respectively. As an example
   255,0,0 is red and 255,255,0 is yellow.

   Alternatively you may specify the color with a single string (as in the
   second line of the synopsis above); this string should contain three
   numbers, separated by commas. As an example "255,0,255" would be violet.
   Using this variant of the colour-command, you may use symbolic names for
   colours:
open window 100,100
yellow$="255,255,0"
color yellow$
text 50,50,"Hallo"

   , which reads much clearer.

Example

open window 255,255
for x=10 to 235 step 10:for y=10 to 235 step 10
        colour x,y,0
        fill rectangle x,y,x+10,y+10
next y:next x
          

   This fills the window with colored rectangles. However, none of the used
   colours contains any shade of blue, because the color-command has always 0
   as a third argument.

See also

   open window, backcolor, line, rectangle, triangle, circle
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Name

   colour - see color

Synopsis

colour red,green,blue
colour "red,green,blue"

See also

   color
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Name

   compile - compile a string with yabasic-code on the fly

Synopsis

compile(code$)

Description

   This is an advanced command (closely related with the execute-command). It
   allows you to compile a string of yabasic-code (which is the only argument).
   Afterwards the compiled code is a normal part of your program.

   Note, that there is no way to remove the compiled code.

Example

compile("sub mysub(a):print a:end sub")
mysub(2)
          

   This example creates a function named mysub, which simply prints its single
   argument.

See also

   execute
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Name

   continue - start the next iteration of a for-, do-, repeat- or while-loop

Synopsis

continue

Description

   You may use continue within any loop to start the next iteration
   immediately. Depending on the type of the loop, the loop-condition will or
   will not be checked. Especially: for- and while-loops will evaluate their
   respective conditions, do- and repeat-loops will not.

   Remark: Another way to change the flow of execution within a loop, is the
   break-command.

Example

for a=1 to 100
  if mod(a,2)=0 continue
  print a
next a
          

   This example will print all odd numbers between 1 and 100.

See also

   for, do, repeat, while, break
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Name

   cos() - return the cosine of its single argument

Synopsis

x=cos(angle)

Description

   The cos-function expects an angle (in radian) and returns its cosine.

Example

print cos(pi)
          

   This example will print -1.

See also

   acos, sin

D

   data - introduces a list of data-items
   date$ - returns a string with various components of the current date
   dec() - convert a base 2 or base 16 number into decimal form
   default - mark the default-branch within a switch-statement
   dim - create an array prior to its first use
   do - start a (conditionless) do-loop
   doc - special comment, which might be retrieved by the program itself
   docu$ - special array, containing the contents of all docu-statement within
          the program

   dot - draw a dot in the graphic-window

Name

   data - introduces a list of data-items

Synopsis

data 9,"world"
...
read b,a$

Description

   The data-keyword introduces a list of comma-separated list of strings or
   numbers, which may be retrieved with the read-command.

   The data-command itself does nothing; it just stores data. A single
   data-command may precede an arbitrarily long list of values, in which
   strings or numbers may be mixed at will.

   yabasic internally uses a data-pointer to keep track of the current location
   within the data-list; this pointer may be reset with the restore-command.

Example

do
  restore
  for a=1 to 4
    read num$,num
    print num$,"=",num
  next a
loop
data "eleven",11,"twelve",12,"thirteen",13,"fourteen",14
          

   This example just prints a series of lines eleven=11 up to fourteen=14 and
   so on without end.

   The restore-command ensures that the list of data-items is read from the
   start with every iteration.

See also

   read, restore
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Name

   date$ - returns a string with various components of the current date

Synopsis

a$=date$

Description

   The date$-function (which must be called without parentheses; i.e. date$()
   would be an error) returns a string containing various components of a date;
   an example would be 4-05-27-2004-Thu-May. This string consists of various
   fields separated by hyphens ("-"):
     * The day within the week as a number in the range 0 (=Sunday) to 6
       (=Saturday) (in the example above: 4, i.e. thursday).
     * The month as a number in the range 1 (=January) to 12 (=December) (in
       the example: 5 which stands for May).
     * The day within the month as a number in the range 1 to 31 (in the
       example: 27).
     * The full, 4-digit year (in the example: 2004, which reminds me that I
       should adjust the clock within my computer ...).
     * The abbreviated name of the day within the week (Mon to Sun).
     * The abbreviated name of the month (Jan to Dec).

   Therefore the whole example above (4-05-27-2004-Thu-May) would read: day 4
   in the week (counting from 0), May 27 in the year 2004, which is a Thursday
   in May.

   Note, that all fields within the string returned by date$ have a fixed with
   (numbers are padded with zeroes); therefore it is easy to extract the
   various fields of a date format with mid$.

Example

rem   Two ways to print the same ...

print mid$(date$,3,10)

dim fields$(6)
a=split(date$,fields$(),"-")
print fields$(2),"-",fields$(3),"-",fields$(4)
          

   This example shows two different techniques to extract components from the
   value returned by date$. The mid$-function is the preferred way, but you
   could just as well split the return-value of date$ at every "-" and store
   the result within an array of strings.

See also

   time$
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Name

   dec() - convert a base 2 or base 16 number into decimal form

Synopsis

a=dec(number$)
a=dec(number$,base)

Description

   The dec-function takes the string-representation of a base-2 or base-16
   (which is the default) number and converts it into a decimal number. The
   optional second argument (base) might