diff options
Diffstat (limited to 'doc')
| -rw-r--r-- | doc/tclvars.n | 13 |
1 files changed, 11 insertions, 2 deletions
diff --git a/doc/tclvars.n b/doc/tclvars.n index df85aea..0c0debb 100644 --- a/doc/tclvars.n +++ b/doc/tclvars.n @@ -5,7 +5,7 @@ '\" See the file "license.terms" for information on usage and redistribution '\" of this file, and for a DISCLAIMER OF ALL WARRANTIES. '\" -'\" RCS: @(#) $Id: tclvars.n,v 1.23 2005/10/01 09:28:40 davidw Exp $ +'\" RCS: @(#) $Id: tclvars.n,v 1.24 2006/04/18 18:05:47 dgp Exp $ '\" .so man.macros .TH tclvars n 8.0 Tcl "Tcl Built-In Commands" @@ -246,6 +246,7 @@ when converting floating-point values to strings. It defaults to 0. \fIApplications should not change this value;\fR it is provided for compatibility with legacy code. .PP +.RS The default value of 0 is special, meaning that Tcl should convert numbers using as few digits as possible while still distinguishing any floating point number from its nearest @@ -254,16 +255,20 @@ for \fItcl_precision\fR in that an inexact number like \fI1.4\fR will convert as \fI1.4\fR rather than \fI1.3999999999999999\fR even though the latter is nearer to the exact value of the binary number. +.RE .VE 8.5 .PP +.RS 17 digits is ``perfect'' for IEEE floating-point in that it allows double-precision values to be converted to strings and back to binary with no loss of information. However, using 17 digits prevents any rounding, which produces longer, less intuitive results. For example, \fBexpr 1.4\fR returns 1.3999999999999999 with \fBtcl_precision\fR set to 17, vs. 1.4 if \fBtcl_precision\fR is 12. +.RE +.PP .RS -All interpreters in a process share a single \fBtcl_precision\fR value: +All interpreters in a thread share a single \fBtcl_precision\fR value: changing it in one interpreter will affect all other interpreters as well. However, safe interpreters are not allowed to modify the variable. @@ -291,8 +296,10 @@ tracking down suspected problems with the Tcl compiler. It is also occasionally useful when converting existing code to use Tcl8.0. .PP +.RS This variable and functionality only exist if \fBTCL_COMPILE_DEBUG\fR was defined during Tcl's compilation. +.RE .TP \fBtcl_traceExec\fR The value of this variable can be set to control @@ -316,8 +323,10 @@ and interpreter. It is also occasionally useful when converting code to use Tcl8.0. .PP +.RS This variable and functionality only exist if \fBTCL_COMPILE_DEBUG\fR was defined during Tcl's compilation. +.RE .TP \fBtcl_wordchars\fR The value of this variable is a regular expression that can be set to |