- experimental 8.7.0~a5+dfsg-3
fpclassify(3tcl) | Tcl Float Classifier | fpclassify(3tcl) |
NAME¶
fpclassify - Floating point number classification of Tcl values
SYNOPSIS¶
package require tcl 8.7
fpclassify value
DESCRIPTION¶
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.
EXAMPLE¶
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"
} }
SEE ALSO¶
expr(3tcl), mathfunc(3tcl)
KEYWORDS¶
floating point
STANDARDS¶
This command depends on the fpclassify() C macro conforming to “ISO C99” (i.e., to ISO/IEC 9899:1999).
COPYRIGHT¶
Copyright © 2018 by Kevin B. Kenny <kennykb@acm.org>. All rights reserved
8.7 | Tcl |