- find the LCD of two natural numbers

- test whether an array of reals is pointwise convergent. Spoiler:

    !grep abs( $array[ $_ ] ) < abs( $array[ $_ + 1 ] ), ( 0..$#array-
+1 );
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- write a program for a robot to explore and map an orthogonal maze 40m x 40m. The robot can see one metre in each of four directions North, South, East or West and perceives the presence or absence of a wall. A wall is a one metre cube. The robot receives only the instructions N, S, E and W (to move one metre in that direction). It then returns four binary digits to your program indicating the presence or absence of walls in these directions and awaits further instructions. If the robot is told to hit a wall, it will, but will emergency shut down after that, so the program must not instruct this. The maze has an entrance and an exit which are interchangeable for these purposes. The goal of the program should be to produce a map of any such maze as efficiently as possible. Include an iteration counter and fail at a million iterations to prevent accidental looping of the program. Communication with the robot takes place via STDIN/STDOUT. (advanced version: extend this to N robots exploring the same maze. Robots cannot discern between walls and other robots. In this case messages to and from robots begin with a numeric robot id followed by a space.)