push-float ket
push the float coefficient c onto the ket label
so that c is now the "value" of the ket
often useful if you want to swap between manipulating the coeff versus the value of a ket
NB: it uses default-decimal-places as the max number of digits to use
NB: the max of which seems to be 5, probably due to the limit in precision of floats
push-float is the approximate inverse of pop-float