programming/glk/floo/model.floo

#FLOO

# model.floo: Model program for Floo, using Glk.
# Designed by Andrew Plotkin <erkyrath@netcom.com>
# http://www.eblong.com/zarf/glk/floo/index.html
# This program is in the public domain.

# This is an even simpler model of a text adventure which uses the Glk API.
# It is written in Floo. If you don't know anything about Floo, start with
# the fact that it's all reverse polish.

# Define an input buffer.
/inbuffer 80 string def

# Define a procedure to draw the status line.
/draw_status_line {
    # Only proceed if there *is* a status line.
    statuswin 0 ne {
        # Set and clear the window
        statuswin glk_set_window
        statuswin glk_window_clear
        # Define a string to put in the window
        /statusstring "Welcome to Floo" def
        # Compute the width of the window...
        statuswin true false glk_window_get_size
        # ...and then compute (win-strlen) / 2.
        statusstring strlen
        sub 2 idiv
        # Move the cursor and print.
        statuswin exch 0 glk_window_move_cursor
        statusstring glk_put_string
        # Reset the window.
        mainwin glk_set_window
    } if
} def

# Now the actual program begins.

# Open the main window.
0 0 0 wintype_TextBuffer 1 glk_window_open
/mainwin exch def

# If we couldn't do that, forget it.
mainwin 0 eq {
    glk_exit
} if

# Open the status window.
mainwin 
winmethod_Above winmethod_Fixed or
1 wintype_TextGrid 2 glk_window_open
/statuswin exch def

# Set the current stream to the main window stream.
mainwin glk_set_window

"Welcome to a simple sample parser in Floo.\n"
glk_put_string
"Type \"help\" for the short list of commands.\n"
glk_put_string

# Begin the program loop.
{
    # Draw the status line, and then print the prompt.
    draw_status_line
    "\n>" glk_put_string
    # Request a line of input.
    mainwin inbuffer 0 glk_request_line_event
    
    # Here's the event loop.
    {
        glk_select /ev exch def
        # ev is now a four-element event array: [type window val1 val2]
        # Define evtype to the first element (type)
        ev 0 get
            /evtype exch def
        # If it was a line input event, exit the event loop.
        evtype evtype_LineInput eq { exit } if
        # If it was a window-arrangement event, redraw the status line.
        evtype evtype_Arrange eq { draw_status_line } if
    } loop
    
    # Trim the buffer down to the returned length.
    inbuffer  ev 2 get  0 put
    
    # Parse the buffer, very simply and stupidly.
    
    inbuffer "quit" eq {
        "Thanks for playing.\n" glk_put_string
        glk_exit
    } if

    inbuffer "jump" eq {
        "You jump.\n" glk_put_string
        continue
    } if
    
    inbuffer "help" eq {
        "This is an even simpler model program.\n\
HELP: Display this list\n\
JUMP: Jump.\n\
QUIT: Quit.\n" glk_put_string
        continue
    } if
    
    inbuffer "" eq {
        continue
    } if
    
    "I don't know the command \"" glk_put_string
    inbuffer glk_put_string 
    "\".\n" glk_put_string
} loop