DAVE%UWF.BITNET@WISCVM.WISC.EDU (09/09/86)
'Ello,
I've been doing a little matrix algebra in C lately, and in the process
I have been wanting to read in some real numbers, preferably thru SCANF, but I
get nothing but 0.000 returned when i try to put the result of a SCANF in a var
declared as DOUBLE. The only thing that I could think of was either writing my
own algorithm, or reading the number in as FLOAT and storing it in the DOUBLE
variable. Perchance someone else has had this problem and found a better
solution without re-inventing several wheels? I guess there really isn't any
reason why I just couldn't use FLOAT variables, but then there shouldn't be any
reason why I can't use SCANF on DOUBLE vars either.
Thanks in advance,
Daveark@alice.UucP (Andrew Koenig) (09/10/86)
> 'Ello, > I've been doing a little matrix algebra in C lately, and in the process > I have been wanting to read in some real numbers, preferably thru SCANF, but I > get nothing but 0.000 returned when i try to put the result of a SCANF in a var > declared as DOUBLE. The only thing that I could think of was either writing my > own algorithm, or reading the number in as FLOAT and storing it in the DOUBLE > variable. Perchance someone else has had this problem and found a better > solution without re-inventing several wheels? I guess there really isn't any > reason why I just couldn't use FLOAT variables, but then there shouldn't be any > reason why I can't use SCANF on DOUBLE vars either. > Thanks in advance, > Dave float f; double d; scanf ("%f", &f); /* should work */ scanf ("%f", &d); /* garbage */ scanf ("%lf", &d); /* should work */ scanf ("%lf", &f); /* garbage */
phnch@phuxc.UUCP (N.C. Hauth [Courtney]) (09/16/86)
Yes, there is a solution to your problem. You have to use the scanf with a long float. For example: sscanf(line,"%*1d %1d %6lf\n",&division_1,&dc1); Happy Hunting. Courtney
apn@nonvon.UUCP (apn) (09/22/86)
In article <3672@brl-smoke.ARPA>, DAVE%UWF.BITNET@WISCVM.WISC.EDU writes: > I have been wanting to read in some real numbers, preferably thru SCANF, but I > get nothing but 0.000 returned when i try to put the result of a SCANF in a var > declared as DOUBLE. The only thing that I could think of was either writing my > own algorithm, or reading the number in as FLOAT and storing it in the DOUBLE What about using atof to read in the float ?
vaughan@orion.UUCP (Robert Vaughan) (09/26/86)
>> I have been wanting to read in some real numbers, preferably thru SCANF >> ... >> declared as DOUBLE. (...) Well, go ahead! K&R, page 149 gives the key to reading in double precision number using the scanf family: "the conversion characters e or f may be preceeded by l (letter l) to indicate that .. a pointer to double rather than float is expected" The code would look like double foo; scanf("%lf",&foo); After having my code bomb several times (unfortunately, I was not as lucky as you - instead of zeroes, I got core dumps), I discovered this little gem in K&R.
kneller@ucsfcgl.UUCP (Don Kneller%Langridge) (09/29/86)
In article <22@orion.UUCP> vaughan@orion.UUCP (Robert Vaughan) writes: >>> I have been wanting to read in some real numbers, preferably thru SCANF >>> ... >>> declared as DOUBLE. (...) > >double foo; > > scanf("%lf",&foo); > Except, of course, in the infinite wisdom of Silicon Graphics whose floats and doubles are the same size so one must use %f for both. The "justification" is that they have yet another floating point type called long float with gets the %lf format. It's painfully nonportable. Sigh. -- Don Kneller UUCP: ...ucbvax!ucsfcgl!kneller ARPA: kneller@cgl.ucsf.edu BITNET: kneller@ucsfcgl.BITNET
chris@umcp-cs.UUCP (Chris Torek) (10/01/86)
In article <9939@cgl.ucsf.edu.ucsfcgl.UUCP> kneller@cgl.ucsf.edu.UUCP (Don Kneller%Langridge) writes: >[In the] Silicon Graphics [compiler] floats and doubles are the same >size so one must use %f for both. The "justification" is that they >have yet another floating point type called long float with gets the >%lf format. It's painfully nonportable. Sigh. Indeed. It may be too late now, but they should have used `long double', and perhaps `%llf'. `long float' is an alias for `double' (per K&R p. 193). (The arrogation of `%lf' is to me more distressing than that of `long float'.) -- In-Real-Life: Chris Torek, Univ of MD Comp Sci Dept (+1 301 454 1516) UUCP: seismo!umcp-cs!chris CSNet: chris@umcp-cs ARPA: chris@mimsy.umd.edu