Ethiopian multiplication: Difference between revisions

=={{header|Metafont}}==

Implemented without the ''tutor''.

<lang metafont>vardef halve(expr x) = floor(x/2) enddef;

vardef double(expr x) = x*2 enddef;

vardef iseven(expr x) = if (x mod 2) = 0: true else: false fi enddef;

primarydef a ethiopicmult b =

begingroup

save r_, plier_, plicand_;

plier_ := a; plicand_ := b;

r_ := 0;

forever: exitif plier_ < 1;

if not iseven(plier_): r_ := r_ + plicand_; fi

plier_ := halve(plier_);

plicand_ := double(plicand_);

endfor

r_

endgroup

enddef;

show( (17 ethiopicmult 34) );

end</lang>