New global control over float print precision.

* configure (have_dbl_decimal_dig): New variable.
New configure test to test for DBL_DECIMAL_DIG
or __DBL_DECIMAL_DIG__, resulting in FLO_MAX_DIG
macro being deposited in config.h.

* arith.c (arith_init): Register flo-max-dig variable.

* stream.c (print_flo_precision_s): New symbol variable.
(formatv): Obtain default precision from *print-flo-precision*
special variable, rather than hard coded DBL_DIG.
(stream_init): Initialize print_flo_precision_s variable,
and register *print-flo-precision* special.

* txr.1: Document flo-max-dig, *print-flo-precision*,
and change of behavior in format.

1 files changed, 32 insertions, 0 deletions

diff --git a/configure b/configure
index 8ee9c4e0..528f77ad 100755
--- a/configure
+++ b/configure
@@ -112,6 +112,7 @@ lit_align=
 extra_debugging=
 debug_support=y
 gen_gc=y
+have_dbl_decimal_dig=
 have_unistd=
 have_sys_time=
 have_syslog=
@@ -1265,6 +1266,37 @@ printf '"%s"\n' "$inline"
 printf "#define INLINE $inline\n" >> $config_h
 
 #
+# DBL_DECIMAL_DIG
+#
+
+printf "Checking for DBL_DECIMAL_DIG ... "
+
+for try_sym in DBL_DECIMAL_DIG __DBL_DECIMAL_DIG__ ; do
+  cat > conftest.c <<!
+#include <float.h>
+
+#ifndef $try_sym
+#error $try_sym not defined
+#else
+int main(void)
+{
+  return 0;
+}
+#endif
+!
+  if conftest ; then
+    printf "yes (%s)\n" $try_sym
+    printf "#define FLO_MAX_DIG $try_sym\n" >> $config_h
+    have_dbl_decimal_dig=y
+  fi
+done
+
+if ! [ $have_dbl_decimal_dig ] ; then
+    printf "no\n"
+    printf "#define FLO_MAX_DIG (DBL_DIG + 2)\n" >> $config_h
+fi
+
+#
 # Valgrind
 #