Provided by: tcl8.5-doc_8.5.19-1_all 

NAME
Tcl_PrintDouble - Convert floating value to string
SYNOPSIS
#include <tcl.h>
Tcl_PrintDouble(interp, value, dst)
ARGUMENTS
Tcl_Interp *interp (in) Before Tcl 8.0, the tcl_precision variable in this interpreter
controlled the conversion. As of Tcl 8.0, this argument is ignored and
the conversion is controlled by the tcl_precision variable that is now
shared by all interpreters.
double value (in) Floating-point value to be converted.
char *dst (out) Where to store the string representing value. Must have at least
TCL_DOUBLE_SPACE characters of storage.
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DESCRIPTION
Tcl_PrintDouble generates a string that represents the value of value and stores it in memory at the
location given by dst. It uses %g format to generate the string, with one special twist: the string is
guaranteed to contain either a “.” or an “e” so that it does not look like an integer. Where %g would
generate an integer with no decimal point, Tcl_PrintDouble adds “.0”. 2
If the tcl_precision value is non-zero, the result will have precisely that many digits of significance. 2
If the value is zero (the default), the result will have the fewest digits needed to represent the number 2
in such a way that Tcl_NewDoubleObj will generate the same number when presented with the given string. 2
IEEE semantics of rounding to even apply to the conversion.
KEYWORDS
conversion, double-precision, floating-point, string
Tcl 8.0 Tcl_PrintDouble(3tcl)