Greetings,
LabWindows/CVI 9.0.1's implementation of <stdio.h> *scanf and <stdlib.h> strtod functions appears not to support reading back "NaN", "Inf", "+Inf" or "-Inf" values, although printf() can generate them. May I suggest to add functionality like described below.
Practical use would be that it's easier to propagate "invalid measurement" through strings if strto*() and *scanf() understand all classes of strings that *printf() family functions will generate.
This suggestion is in alignment with ISO 9899:1999 (withdrawn) and its successor ISO 9899:2011, i. e. C99 and C11. Note that there is a "stronger" suggestion to implement all of the C11 standard library in the idea exchange already, which - if implemented - would subsume this suggestion, but as the bare minimum, I'd certainly appreciate seeing this in CVI 2012.
Demo code:
printf("%g\n", -NotANumber());
printf("%+g\n", PositiveInfinity());
printf("%g\n", NegativeInfinity());
double x = 0; int i;
i = sscanf("NaN", "%lf", &x); printf("i=%d, x=%g\n", i, x);
i = sscanf("Inf", "%lf", &x); printf("i=%d, x=%g\n", i, x);
errno = 0; x = strtod("NaN", NULL); printf("x=%g, errno=%d\n", x, errno);
Desired result:
-NaN
+Inf
-Inf
i=1, x=NaN
i=1, x=Inf
x=NaN, errno=0
Actual result: we see that printf supports NaN/Inf, but scanf and strtod do not:
NaN
+Inf
-Inf
i=0, x=0
i=0, x=0
x=0, errno=0
Thank you.
