12.6.1.1470
F>D
f-to-d
FLOATING
 
( -- d ) ( F: r -- ) or ( r -- d )

d is the double-cell signed-integer equivalent of the integer portion of r. The fractional portion of r is discarded. An ambiguous condition exists if the integer portion of r cannot be represented as a double-cell signed integer.

Note:
Rounding the floating-point value prior to calling F>D is advised, because F>D rounds towards zero.