Info: (asymptote) Interactive mode

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 10 Interactive mode
 *******************
 
 Interactive mode is entered by executing the command 'asy' with no file
 arguments.  When the '-multiline' option is disabled (the default), each
 line must be a complete 'Asymptote' statement (unless explicitly
 continued by a final backslash character '\'); it is not necessary to
 terminate input lines with a semicolon.  If one assigns
 'settings.multiline=true', interactive code can be entered over multiple
 lines; in this mode, the automatic termination of interactive input
 lines by a semicolon is inhibited.  Multiline mode is useful for cutting
 and pasting 'Asymptote' code directly into the interactive input buffer.
 
    Interactive mode can be conveniently used as a calculator:
 expressions entered at the interactive prompt (for which a corresponding
 'write' function exists) are automatically evaluated and written to
 'stdout'.  If the expression is non-writable, its type signature will be
 printed out instead.  In either case, the expression can be referred to
 using the symbol '%' in the next line input at the prompt.  For example:
 > 2+3
 5
 > %*4
 20
 > 1/%
 0.05
 > sin(%)
 0.0499791692706783
 > currentpicture
 <picture currentpicture>
 > %.size(200,0)
 >
 
    The '%' symbol, when used as a variable, is shorthand for the
 identifier 'operator answer', which is set by the prompt after each
 written expression evaluation.
 
    The following special commands are supported only in interactive mode
 and must be entered immediately after the prompt:
 
 'help'
      view the manual;
 'erase'
      erase 'currentpicture';
 'reset'
      reset the 'Asymptote' environment to its initial state, except for
      changes to the settings module (settings), the current
      directory (cd), and breakpoints (Debugger);
 'input FILE'
      does an interactive reset, followed by the command 'include FILE'.
      If the file name 'FILE' contains nonalphanumeric characters,
      enclose it with quotation marks.  A trailing semi-colon followed by
      optional 'Asymptote' commands may be entered on the same line.
 'quit'
      exit interactive mode ('exit' is a synonym; the abbreviation 'q' is
      also accepted unless there exists a top-level variable named 'q').
      A history of the most recent 1000 (this number can be changed with
      the 'historylines' configuration variable) previous commands will
      be retained in the file '.asy/history' in the user's home directory
      (unless the command-line option '-localhistory' was specified, in
      which case the history will be stored in the file '.asy_history' in
      the current directory).
 
    Typing 'ctrl-C' interrupts the execution of 'Asymptote' code and
 returns control to the interactive prompt.
 
    Interactive mode is implemented with the GNU 'readline' library, with
 command history and auto-completion.  To customize the key bindings,
 see: <http://cnswww.cns.cwru.edu/php/chet/readline/readline.html>
 
    The file 'asymptote.py' in the 'Asymptote' system directory provides
 an alternative way of entering 'Asymptote' commands interactively,
 coupled with the full power of 'Python'.  Copy this file to your 'Python
 path' and then execute from within 'Python' the commands
 from asymptote import *
 g=asy()
 g.size(200)
 g.draw("unitcircle")
 g.send("draw(unitsquare)")
 g.fill("unitsquare, blue")
 g.clip("unitcircle")
 g.label("\"$O$\", (0,0), SW")