Print float values with full precision.

src/libexpr/eval.cc

@@ -16,6 +16,7 @@
 #include <sys/time.h>
 #include <sys/resource.h>
 #include <iostream>
+#include <iomanip>
 #include <fstream>
 
 #include <sys/resource.h>
@@ -125,7 +126,7 @@ static void printValue(std::ostream & str, std::set<const Value *> & active, con
         str << *v.external;
         break;
     case tFloat:
-        str << v.fpoint;
+        str << std::setprecision(std::numeric_limits<double>::max_digits10) << v.fpoint;
         break;
     default:
         throw Error("invalid value");

src/libexpr/nixexpr.cc

@@ -3,6 +3,7 @@
 #include "util.hh"
 
 #include <cstdlib>
+#include <iomanip>
 
 
 namespace nix {
@@ -70,7 +71,7 @@ void ExprInt::show(std::ostream & str) const
 
 void ExprFloat::show(std::ostream & str) const
 {
-    str << nf;
+    str << std::setprecision(std::numeric_limits<double>::max_digits10) << nf;
 }
 
 void ExprString::show(std::ostream & str) const

src/libutil/json.cc

@@ -30,8 +30,8 @@ template<> void toJSON<long>(std::ostream & str, const long & n) { str << n; }
 template<> void toJSON<unsigned long>(std::ostream & str, const unsigned long & n) { str << n; }
 template<> void toJSON<long long>(std::ostream & str, const long long & n) { str << n; }
 template<> void toJSON<unsigned long long>(std::ostream & str, const unsigned long long & n) { str << n; }
-template<> void toJSON<float>(std::ostream & str, const float & n) { str << n; }
-template<> void toJSON<double>(std::ostream & str, const double & n) { str << n; }
+template<> void toJSON<float>(std::ostream & str, const float & n) { str << std::setprecision(std::numeric_limits<float>::max_digits10) << n; }
+template<> void toJSON<double>(std::ostream & str, const double & n) { str << std::setprecision(std::numeric_limits<double>::max_digits10) << n; }
 
 template<> void toJSON<std::string>(std::ostream & str, const std::string & s)
 {

tests/lang/eval-okay-float.exp

@@ -1 +1 @@
-[ 3.4 3.5 2.5 1.5 ]
+[ 3.3999999999999999 3.5 2.5 1.5 ]

tests/lang/eval-okay-fromTOML.exp

@@ -1 +1 @@
-[ { clients = { data = [ [ "gamma" "delta" ] [ 1 2 ] ]; hosts = [ "alpha" "omega" ]; }; database = { connection_max = 5000; enabled = true; ports = [ 8001 8001 8002 ]; server = "192.168.1.1"; }; owner = { name = "Tom Preston-Werner"; }; servers = { alpha = { dc = "eqdc10"; ip = "10.0.0.1"; }; beta = { dc = "eqdc10"; ip = "10.0.0.2"; }; }; title = "TOML Example"; } { "1234" = "value"; "127.0.0.1" = "value"; a = { b = { c = { }; }; }; arr1 = [ 1 2 3 ]; arr2 = [ "red" "yellow" "green" ]; arr3 = [ [ 1 2 ] [ 3 4 5 ] ]; arr4 = [ "all" "strings" "are the same" "type" ]; arr5 = [ [ 1 2 ] [ "a" "b" "c" ] ]; arr7 = [ 1 2 3 ]; arr8 = [ 1 2 ]; bare-key = "value"; bare_key = "value"; bin1 = 214; bool1 = true; bool2 = false; "character encoding" = "value"; d = { e = { f = { }; }; }; dog = { "tater.man" = { type = { name = "pug"; }; }; }; flt1 = 1; flt2 = 3.1415; flt3 = -0.01; flt4 = 5e+22; flt5 = 1e+06; flt6 = -0.02; flt7 = 6.626e-34; flt8 = 9.22462e+06; fruit = [ { name = "apple"; physical = { color = "red"; shape = "round"; }; variety = [ { name = "red delicious"; } { name = "granny smith"; } ]; } { name = "banana"; variety = [ { name = "plantain"; } ]; } ]; g = { h = { i = { }; }; }; hex1 = 3735928559; hex2 = 3735928559; hex3 = 3735928559; int1 = 99; int2 = 42; int3 = 0; int4 = -17; int5 = 1000; int6 = 5349221; int7 = 12345; j = { "ʞ" = { l = { }; }; }; key = "value"; key2 = "value"; name = "Orange"; oct1 = 342391; oct2 = 493; physical = { color = "orange"; shape = "round"; }; products = [ { name = "Hammer"; sku = 738594937; } { } { color = "gray"; name = "Nail"; sku = 284758393; } ]; "quoted \"value\"" = "value"; site = { "google.com" = true; }; str = "I'm a string. \"You can quote me\". Name\tJosé\nLocation\tSF."; table-1 = { key1 = "some string"; key2 = 123; }; table-2 = { key1 = "another string"; key2 = 456; }; x = { y = { z = { w = { animal = { type = { name = "pug"; }; }; name = { first = "Tom"; last = "Preston-Werner"; }; point = { x = 1; y = 2; }; }; }; }; }; "ʎǝʞ" = "value"; } { metadata = { "checksum aho-corasick 0.6.4 (registry+https://github.com/rust-lang/crates.io-index)" = "d6531d44de723825aa81398a6415283229725a00fa30713812ab9323faa82fc4"; "checksum ansi_term 0.11.0 (registry+https://github.com/rust-lang/crates.io-index)" = "ee49baf6cb617b853aa8d93bf420db2383fab46d314482ca2803b40d5fde979b"; "checksum ansi_term 0.9.0 (registry+https://github.com/rust-lang/crates.io-index)" = "23ac7c30002a5accbf7e8987d0632fa6de155b7c3d39d0067317a391e00a2ef6"; "checksum arrayvec 0.4.7 (registry+https://github.com/rust-lang/crates.io-index)" = "a1e964f9e24d588183fcb43503abda40d288c8657dfc27311516ce2f05675aef"; }; package = [ { dependencies = [ "memchr 2.0.1 (registry+https://github.com/rust-lang/crates.io-index)" ]; name = "aho-corasick"; source = "registry+https://github.com/rust-lang/crates.io-index"; version = "0.6.4"; } { name = "ansi_term"; source = "registry+https://github.com/rust-lang/crates.io-index"; version = "0.9.0"; } { dependencies = [ "libc 0.2.42 (registry+https://github.com/rust-lang/crates.io-index)" "termion 1.5.1 (registry+https://github.com/rust-lang/crates.io-index)" "winapi 0.3.5 (registry+https://github.com/rust-lang/crates.io-index)" ]; name = "atty"; source = "registry+https://github.com/rust-lang/crates.io-index"; version = "0.2.10"; } ]; } { a = [ [ { b = true; } ] ]; c = [ [ { d = true; } ] ]; e = [ [ 123 ] ]; } ]
+[ { clients = { data = [ [ "gamma" "delta" ] [ 1 2 ] ]; hosts = [ "alpha" "omega" ]; }; database = { connection_max = 5000; enabled = true; ports = [ 8001 8001 8002 ]; server = "192.168.1.1"; }; owner = { name = "Tom Preston-Werner"; }; servers = { alpha = { dc = "eqdc10"; ip = "10.0.0.1"; }; beta = { dc = "eqdc10"; ip = "10.0.0.2"; }; }; title = "TOML Example"; } { "1234" = "value"; "127.0.0.1" = "value"; a = { b = { c = { }; }; }; arr1 = [ 1 2 3 ]; arr2 = [ "red" "yellow" "green" ]; arr3 = [ [ 1 2 ] [ 3 4 5 ] ]; arr4 = [ "all" "strings" "are the same" "type" ]; arr5 = [ [ 1 2 ] [ "a" "b" "c" ] ]; arr7 = [ 1 2 3 ]; arr8 = [ 1 2 ]; bare-key = "value"; bare_key = "value"; bin1 = 214; bool1 = true; bool2 = false; "character encoding" = "value"; d = { e = { f = { }; }; }; dog = { "tater.man" = { type = { name = "pug"; }; }; }; flt1 = 1; flt2 = 3.1415000000000002; flt3 = -0.01; flt4 = 4.9999999999999996e+22; flt5 = 1000000; flt6 = -0.02; flt7 = 6.6259999999999998e-34; flt8 = 9224617.4459912274; fruit = [ { name = "apple"; physical = { color = "red"; shape = "round"; }; variety = [ { name = "red delicious"; } { name = "granny smith"; } ]; } { name = "banana"; variety = [ { name = "plantain"; } ]; } ]; g = { h = { i = { }; }; }; hex1 = 3735928559; hex2 = 3735928559; hex3 = 3735928559; int1 = 99; int2 = 42; int3 = 0; int4 = -17; int5 = 1000; int6 = 5349221; int7 = 12345; j = { "ʞ" = { l = { }; }; }; key = "value"; key2 = "value"; name = "Orange"; oct1 = 342391; oct2 = 493; physical = { color = "orange"; shape = "round"; }; products = [ { name = "Hammer"; sku = 738594937; } { } { color = "gray"; name = "Nail"; sku = 284758393; } ]; "quoted \"value\"" = "value"; site = { "google.com" = true; }; str = "I'm a string. \"You can quote me\". Name\tJosé\nLocation\tSF."; table-1 = { key1 = "some string"; key2 = 123; }; table-2 = { key1 = "another string"; key2 = 456; }; x = { y = { z = { w = { animal = { type = { name = "pug"; }; }; name = { first = "Tom"; last = "Preston-Werner"; }; point = { x = 1; y = 2; }; }; }; }; }; "ʎǝʞ" = "value"; } { metadata = { "checksum aho-corasick 0.6.4 (registry+https://github.com/rust-lang/crates.io-index)" = "d6531d44de723825aa81398a6415283229725a00fa30713812ab9323faa82fc4"; "checksum ansi_term 0.11.0 (registry+https://github.com/rust-lang/crates.io-index)" = "ee49baf6cb617b853aa8d93bf420db2383fab46d314482ca2803b40d5fde979b"; "checksum ansi_term 0.9.0 (registry+https://github.com/rust-lang/crates.io-index)" = "23ac7c30002a5accbf7e8987d0632fa6de155b7c3d39d0067317a391e00a2ef6"; "checksum arrayvec 0.4.7 (registry+https://github.com/rust-lang/crates.io-index)" = "a1e964f9e24d588183fcb43503abda40d288c8657dfc27311516ce2f05675aef"; }; package = [ { dependencies = [ "memchr 2.0.1 (registry+https://github.com/rust-lang/crates.io-index)" ]; name = "aho-corasick"; source = "registry+https://github.com/rust-lang/crates.io-index"; version = "0.6.4"; } { name = "ansi_term"; source = "registry+https://github.com/rust-lang/crates.io-index"; version = "0.9.0"; } { dependencies = [ "libc 0.2.42 (registry+https://github.com/rust-lang/crates.io-index)" "termion 1.5.1 (registry+https://github.com/rust-lang/crates.io-index)" "winapi 0.3.5 (registry+https://github.com/rust-lang/crates.io-index)" ]; name = "atty"; source = "registry+https://github.com/rust-lang/crates.io-index"; version = "0.2.10"; } ]; } { a = [ [ { b = true; } ] ]; c = [ [ { d = true; } ] ]; e = [ [ 123 ] ]; } ]

tests/lang/eval-okay-tojson.exp

@@ -1 +1 @@
-"{\"a\":123,\"b\":-456,\"c\":\"foo\",\"d\":\"foo\\n\\\"bar\\\"\",\"e\":true,\"f\":false,\"g\":[1,2,3],\"h\":[\"a\",[\"b\",{\"foo\\nbar\":{}}]],\"i\":3,\"j\":1.44,\"k\":\"foo\"}"
+"{\"a\":123,\"b\":-456,\"c\":\"foo\",\"d\":\"foo\\n\\\"bar\\\"\",\"e\":true,\"f\":false,\"g\":[1,2,3],\"h\":[\"a\",[\"b\",{\"foo\\nbar\":{}}]],\"i\":3,\"j\":1.4399999999999999,\"k\":\"foo\",\"l\":50.03125}"

tests/lang/eval-okay-tojson.nix

@@ -10,4 +10,5 @@ builtins.toJSON
     i = 1 + 2;
     j = 1.44;
     k = { __toString = self: self.a; a = "foo"; };
+    l = 50.03125;
   }