[bug-gawk] Gawk and NaN values

[Hermann Peifer]

Hi,

The manual states on p. 346 about nan and inf:

--- snip ---
gawk interprets the four strings ‘+inf’, ‘-inf’, ‘+nan’, and ‘-nan’ 
specially, producing the corresponding special numeric values. The 
leading sign acts a signal to gawk (and the user) that the value is 
really numeric... For example:

$ echo +nan | gawk '{ print $1 + 0 }'
-| nan
--- snip ---

The result above is 'nan', i.e. a string without a leading sign which 
means that subsequent awk processing will not detect that this is meant 
to be a special value. Simplified example:

$ echo "1 -nan" | awk '{ print $1, $1 / $2 }'
1 nan

$ echo "1 -nan" | awk '{ print $1, $1 / $2 }' | awk '{print $1 / $2}'
awk: cmd. line:1: (FILENAME=- FNR=1) fatal: division by zero attempted

This might well be a feature rather than anything else. I just came 
across it today and thought it could be worth reporting.

Hermann