- NAME
- fpclassify — Floating point number classification of Tcl values
- SYNOPSIS
- DESCRIPTION
- zero
- subnormal
- normal
- infinite
- nan
- EXAMPLE
- SEE ALSO
- KEYWORDS
- STANDARDS
- COPYRIGHT
fpclassify — Floating point number classification of Tcl values
package require tcl 8.7
fpclassify value
The fpclassify command takes a floating point number, value, and
returns one of the following strings that describe it:
- zero
-
value is a floating point zero.
- subnormal
-
value is the result of a gradual underflow.
- normal
-
value is an ordinary floating-point number (not zero, subnormal,
infinite, nor NaN).
- infinite
-
value is a floating-point infinity.
- nan
-
value is Not-a-Number.
The fpclassify command throws an error if value is not a floating-point
value and cannot be converted to one.
This shows how to check whether the result of a computation is numerically
safe or not. (Note however that it does not guard against numerical errors;
just against representational problems.)
set value [command-that-computes-a-value]
switch [fpclassify $value] {
normal - zero {
puts "Result is $value"
}
infinite {
puts "Result is infinite"
}
subnormal {
puts "Result is $value - WARNING! precision lost"
}
nan {
puts "Computation completely failed"
}
}
expr, mathfunc
floating point
This command depends on the fpclassify() C macro conforming to
“ISO C99”
(i.e., to ISO/IEC 9899:1999).
Copyright © 2018 by Kevin B. Kenny <[email protected]>. All rights reserved
Copyright © 2018 Kevin B. Kenny <kennykb(at)acm.org>. All rights reserved
Copyright © 2019 Donal Fellows