Maze in TCL

maze.tcl

#!/usr/bin/env tclsh --

set maze [list [list 2 2 2 2 2 2 2 2 2] \
               [list 0 0 2 2 2 2 0 2 2] \
               [list 2 0 0 0 0 0 0 0 2] \
               [list 2 0 2 2 0 2 2 0 2] \
               [list 0 2 0 2 0 2 2 0 2] \
               [list 2 2 0 2 0 2 2 0 2] \
               [list 2 2 0 2 0 0 0 0 2] \
               [list 2 2 0 2 0 2 2 2 2] \
               [list 2 2 2 2 0 2 2 2 2]]

proc lpop {listVar} {
        upvar 1 $listVar l
        set r [lindex $l end]
        set l [lreplace $l [set l end] end] ; # Make sure [lreplace] operates on unshared object
        return $r
}

proc is_empty {listVar} {
    upvar 1 $listVar l
    return [expr {[llength $l] == 0}]
}

proc print_maze {} {
    global maze
    for {set x 0} {$x < 9} {incr x} {
        for {set y 0} {$y < 10} {incr y} {
            if {[lindex $maze $x $y] == 2} {
                puts -nonewline {■}
            } elseif {[lindex $maze $x $y] == 1} {
                puts -nonewline {☆}
            } else {
                puts -nonewline {□}
            }
        }
        puts {}
    }
}

proc visit {listVar x y} {
    global maze
    upvar 1 $listVar l
    lset maze $x $y 1
    lappend l [list $x $y]
    puts "$x $y"
}

proc main {} {
    global maze
    print_maze
    set x 1
    set y 0
    lappend stack [list $x $y]
    while {! [is_empty stack]} {
        set p [lpop stack]
        set x [lindex $p 0]
        set y [lindex $p 1]
        if {$x == 8 && $y == 4} {
            break
        }
        if {$x+1 < 9 && [lindex $maze $x+1 $y] == 0} {
            visit stack [expr {$x+1}] $y
        }
        if {$y+1 < 9 && [lindex $maze $x $y+1] == 0} {
            visit stack $x [expr {$y+1}]
        }
        if {$x-1 >= 0 && [lindex $maze $x-1 $y] == 0} {
            visit stack [expr {$x-1}] $y
        }
        if {$y-1 >= 0 && [lindex $maze $x $y-1] == 0} {
            visit stack $x [expr {$y-1}]
        }
    }
    print_maze
}

main