In the Fortran version of MNBRAK (also in the C version) a part of the statement for "computing U by parabolic extension" has the code SIGN(MAX(ABS(Q-R),TINY),Q-R). This just doesn't make sense to me. Shouldn't there be only 1 argument to SIGN? Should this really be MAX(ABS(Q-R),TINY)*SIGN(Q-R)?:confused:

in fact this is not a bug, in fact the function SIGN(a, b) returns the value
abs(a) * sign(b), where sign(b) is the normal sign function.