[gnuastro-commits] master b0efc465: Library (type.c): gal_type_to_string uses 6 and 14 digits for floats

[Mohammad Akhlaghi]

branch: master
commit b0efc465a21a2b1b4a85f94484dccac396b3d543
Author: Mohammad Akhlaghi <mohammad@akhlaghi.org>
Commit: Mohammad Akhlaghi <mohammad@akhlaghi.org>

    Library (type.c): gal_type_to_string uses 6 and 14 digits for floats
    
    Until now, this function (which is used to print numbers as strings) was
    using '%.6g' and '%.10g' for 32-bit and 64-bit floating point
    numbers. However, the '%g' format will (in some situations) not print
    statistically significant digits and generally, it is hard to predict if it
    will print a fixed point or exponential notation.
    
    With this commit, the printing formats for this function have been changed
    to '%.6f' and '%.14f'. This will always print fixed point, and will print
    the required number of digits after the decimal point. Making the result
    more predictable and without any possible loss of precision.
---
 lib/type.c | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/lib/type.c b/lib/type.c
index 8f1d5086..1ca0b49f 100644
--- a/lib/type.c
+++ b/lib/type.c
@@ -427,8 +427,13 @@ gal_type_to_string(void *ptr, uint8_t type, int 
quote_if_str_has_space)
     case GAL_TYPE_INT32:   TO_STRING( int32_t,  "%"PRId32 );  break;
     case GAL_TYPE_UINT64:  TO_STRING( uint64_t, "%"PRIu64 );  break;
     case GAL_TYPE_INT64:   TO_STRING( int64_t,  "%"PRId64 );  break;
-    case GAL_TYPE_FLOAT32: TO_STRING( float,    "%.6g"    );  break;
-    case GAL_TYPE_FLOAT64: TO_STRING( double,   "%.10g"   );  break;
+
+    /* We aren't using '%g' for floating points because it can remove
+       statisically significant digits in some scenarios and its result is
+       generally not easily predictable (can be fixed-point or
+       exponential). The most conservative format is therefore '%f'. */
+    case GAL_TYPE_FLOAT32: TO_STRING( float,    "%.6f"    );  break;
+    case GAL_TYPE_FLOAT64: TO_STRING( double,   "%.14f"   );  break;
 
     default:
       error(EXIT_FAILURE, 0, "%s: type code %d not recognized",