NAME

       fpclassify - Floating point number classification of Tcl values

SYNOPSIS

       package require tcl 9.0

       fpclassify value
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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 Kevin B. Kenny <kennykb@acm.org>. All rights reserved

Tcl                                                    9.0                                      fpclassify(3tcl)