Ethiopian multiplication: Difference between revisions

=={{header|Ursala}}==

The first implementation below relies on the representation of natural numbers as lists of bits,

lsb first, so that halving is the same as taking the tail, doubling

is inserting a zero, and filtering for oddness is filtering by the head,

all of which are expressible as primitives.

<lang Ursala>

#import nat

emul = @lrtK33PDNlCrXK9rhPFlS sum:-0

</lang>

Here is a more verbose version (in keeping with the spirit of the task) treating natural numbers

as abstract types, and explicitly using the operators for distribution (*-), triangular iteration (|\),

and filtering (*~) among others.

<lang Ursala>

#import nat

emul = sum:-0@rS+ (odd@l)*~+ ^|(~&,double)|\+ *-^|\~& @iNC ~&h->tx :^/half@h ~&

</lang>

test program:

<lang Ursala>

#cast %n

test = emul(34,17)

</lang>

output:

<pre>

578

</pre>