diff options
Diffstat (limited to 'doc')
| -rw-r--r-- | doc/PrintDbl.3 | 9 | ||||
| -rw-r--r-- | doc/tclvars.n | 57 |
2 files changed, 3 insertions, 63 deletions
diff --git a/doc/PrintDbl.3 b/doc/PrintDbl.3 index 99b0113..baa415c 100644 --- a/doc/PrintDbl.3 +++ b/doc/PrintDbl.3 @@ -18,10 +18,7 @@ Tcl_PrintDouble \- Convert floating value to string .SH ARGUMENTS .AS Tcl_Interp *interp out .AP Tcl_Interp *interp in -Before Tcl 8.0, the \fBtcl_precision\fR variable in this interpreter -controlled the conversion. As of Tcl 8.0, this argument is ignored and -the conversion is controlled by the \fBtcl_precision\fR variable -that is now shared by all interpreters. +This argument is ignored. .AP double value in Floating-point value to be converted. .AP char *dst out @@ -41,9 +38,7 @@ so that it does not look like an integer. Where \fB%g\fR would generate an integer with no decimal point, \fBTcl_PrintDouble\fR adds .QW .0 . .PP -If the \fBtcl_precision\fR value is non-zero, the result will have -precisely that many digits of significance. If the value is zero -(the default), the result will have the fewest digits needed to +The string generated has the fewest digits needed to represent the number in such a way that \fBTcl_NewDoubleObj\fR will generate the same number when presented with the given string. IEEE semantics of rounding to even apply to the conversion. diff --git a/doc/tclvars.n b/doc/tclvars.n index 44a8e11..2ea08c9 100644 --- a/doc/tclvars.n +++ b/doc/tclvars.n @@ -10,7 +10,7 @@ .BS '\" Note: do not modify the .SH NAME line immediately below! .SH NAME -argc, argv, argv0, auto_path, env, errorCode, errorInfo, tcl_interactive, tcl_library, tcl_nonwordchars, tcl_patchLevel, tcl_pkgPath, tcl_platform, tcl_precision, tcl_rcFileName, tcl_traceCompile, tcl_traceEval, tcl_wordchars, tcl_version \- Variables used by Tcl +argc, argv, argv0, auto_path, env, errorCode, errorInfo, tcl_interactive, tcl_library, tcl_nonwordchars, tcl_patchLevel, tcl_pkgPath, tcl_platform, tcl_rcFileName, tcl_traceCompile, tcl_traceEval, tcl_wordchars, tcl_version \- Variables used by Tcl .BE .SH DESCRIPTION .PP @@ -356,61 +356,6 @@ This gives the size of the native-machine word in bytes (strictly, it is same as the result of evaluating \fIsizeof(long)\fR in C.) .RE .TP -\fBtcl_precision\fR -. -This variable controls the number of digits to generate -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 -neighbours. It differs from using an arbitrarily high value -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 -.PP -.RS -If \fBtcl_precision\fR is not zero, then when Tcl converts a floating -point number, it creates a decimal representation of at most -\fBtcl_precision\fR significant digits; the result may be shorter if -the shorter result represents the original number exactly. If no -result of at most \fBtcl_precision\fR digits is an exact representation -of the original number, the one that is closest to the original -number is chosen. -If the original number lies precisely between two equally accurate -decimal representations, then the one with an even value for the least -significant digit is chosen; for instance, if \fBtcl_precision\fR is 3, then -0.3125 will convert to 0.312, not 0.313, while 0.6875 will convert to -0.688, not 0.687. Any string of trailing zeroes that remains is trimmed. -.RE -.PP -.RS -a \fBtcl_precision\fR value of 17 digits is -.QW 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. For this reason, you will often -see it as a value in legacy code that must run on Tcl versions before -8.5. It is no longer recommended; as noted above, a zero value is the -preferred method. -.RE -.PP -.RS -All interpreters in a thread share a single \fBtcl_precision\fR value: -changing it in one interpreter will affect all other interpreters as -well. Safe interpreters are not allowed to modify the -variable. -.RE -.PP -.RS -Valid values for \fBtcl_precision\fR range from 0 to 17. -.RE -.TP \fBtcl_rcFileName\fR . This variable is used during initialization to indicate the name of a |