'\"
'\" Copyright (c) 2018 Kevin B. Kenny <kennykb@acm.org>. All rights reserved
'\" Copyright (c) 2019 Donal Fellows
'\"
'\" See the file "license.terms" for information on usage and redistribution
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.TH fpclassify n 9.0 Tcl "Tcl Float Classifier"
.so man.macros
.BS
'\" Note:  do not modify the .SH NAME line immediately below!
.SH NAME
fpclassify \- Floating point number classification of Tcl values
.SH SYNOPSIS
\fBpackage require tcl 9.0\fR
.sp
\fBfpclassify \fIvalue\fR
.BE
.SH DESCRIPTION
The \fBfpclassify\fR command takes a floating point number, \fIvalue\fR, and
returns one of the following strings that describe it:
.IP \fBzero\fR
\fIvalue\fR is a floating point zero.
.IP \fBsubnormal\fR
\fIvalue\fR is the result of a gradual underflow.
.IP \fBnormal\fR
\fIvalue\fR is an ordinary floating-point number (not zero, subnormal,
infinite, nor NaN).
.IP \fBinfinite\fR
\fIvalue\fR is a floating-point infinity.
.IP \fBnan\fR
\fIvalue\fR is Not-a-Number.
.PP
The \fBfpclassify\fR command throws an error if value is not a floating-point
value and cannot be converted to one.
.SH EXAMPLE
.PP
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.)
.PP
.CS
set value [command-that-computes-a-value]
switch [\fBfpclassify\fR $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"
    }
}
.CE
.SH "SEE ALSO"
expr(n), mathfunc(n)
.SH KEYWORDS
floating point
.SH STANDARDS
This command depends on the \fBfpclassify\fR() C macro conforming to
.QW "ISO C99"
(i.e., to ISO/IEC 9899:1999).
.SH COPYRIGHT
.nf
Copyright \(co 2018 Kevin B. Kenny <kennykb@acm.org>. All rights reserved
.fi
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