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How to judge if it is a number in C++

How to judge if it is a number in C++# Programming - 葵花宝典

n*r2007-01-31 08:01

1 楼

in C++ How to judge a variable is a number (double type) or N/A, anybody
could help. I spent several hours in searching the document. Thanks very
much!

h*k2007-01-31 08:01

2 楼

wot do u mean judge a variable?
a variable should declared first, then u know the type

X*r2007-01-31 08:01

3 楼

Google "IEEE 754"
e.g. on http://steve.hollasch.net/cgindex/coding/ieeefloat.html , see the "Summary" section.

anybody

【在 n*******r 的大作中提到】

: in C++ How to judge a variable is a number (double type) or N/A, anybody
: could help. I spent several hours in searching the document. Thanks very
: much!

n*e2007-01-31 08:01

4 楼

#include
numeric_limits::quiet_NaN()
Actually there should be many representation of NaN for IEE754
So to determine whether a number is NaN one use isnan(double) in math.h

anybody

【在 n*******r 的大作中提到】

: in C++ How to judge a variable is a number (double type) or N/A, anybody
: could help. I spent several hours in searching the document. Thanks very
: much!