# HG changeset patch
# User jbe
# Date 1407693876 -7200
# Node ID e61bf25f3d04d5fe4cb337abc18d96222231094a
# Parent  2c0db49591be4d17e47decb6d256948c4f72fc59
Dynamic determination of decimal floating point precision in json.export(...)

diff -r 2c0db49591be -r e61bf25f3d04 libraries/json/json.c
--- a/libraries/json/json.c	Sun Aug 10 19:48:09 2014 +0200
+++ b/libraries/json/json.c	Sun Aug 10 20:04:36 2014 +0200
@@ -1093,8 +1093,12 @@
       if (isnan(num)) return luaL_error(L, "JSON export not possible for NaN value");
       // throw error if number is positive or negative infinity:
       if (isinf(num)) return luaL_error(L, "JSON export not possible for infinite numbers");
-      // add Lua's string encoding of the number to the output buffer:
-      sprintf(numstr, "%.17g", num);
+      // determine necessary precision to represent double precision floating point number:
+      sprintf(numstr, "%.14g", num);
+      if (strtod(numstr, NULL) != num) sprintf(numstr, "%.15g", num);
+      if (strtod(numstr, NULL) != num) sprintf(numstr, "%.16g", num);
+      if (strtod(numstr, NULL) != num) sprintf(numstr, "%.17g", num);
+      // add string encoding of the number to the output buffer:
       luaL_addstring(&buf, numstr);
       break;
     // value to encode is of type boolean: