-d:nimPreviewFloatRoundtrip becomes the default (#24217)

changelog.md

@@ -3,6 +3,10 @@
 
 ## Changes affecting backward compatibility
 
+- `-d:nimPreviewFloatRoundtrip` becomes the default. `system.addFloat` and `system.$` now can produce string representations of
+floating point numbers that are minimal in size and possess round-trip and correct
+rounding guarantees (via the
+[Dragonbox](https://raw.githubusercontent.com/jk-jeon/dragonbox/master/other_files/Dragonbox.pdf) algorithm). Use `-d:nimLegacySprintf` to emulate old behaviors.
 
 ## Standard library additions and changes
 

compiler/nim.cfg

@@ -4,7 +4,6 @@ hint[XDeclaredButNotUsed]:off
 
 define:booting
 define:nimcore
-define:nimPreviewFloatRoundtrip
 define:nimPreviewSlimSystem
 define:nimPreviewCstringConversion
 define:nimPreviewProcConversion

lib/std/formatfloat.nim

@@ -79,10 +79,10 @@ proc writeFloatToBufferSprintf*(buf: var array[65, char]; value: BiggestFloat):
       result = 3
 
 proc writeFloatToBuffer*(buf: var array[65, char]; value: BiggestFloat | float32): int {.inline.} =
-  when defined(nimPreviewFloatRoundtrip) or defined(nimPreviewSlimSystem):
-    writeFloatToBufferRoundtrip(buf, value)
-  else:
+  when defined(nimLegacySprintf):
     writeFloatToBufferSprintf(buf, value)
+  else:
+    writeFloatToBufferRoundtrip(buf, value)
 
 proc addFloatRoundtrip*(result: var string; x: float | float32) =
   when nimvm:
@@ -127,10 +127,10 @@ proc addFloat*(result: var string; x: float | float32) {.inline.} =
     s.addFloat(45.67)
     assert s == "foo:45.67"
   template impl =
-    when defined(nimPreviewFloatRoundtrip) or defined(nimPreviewSlimSystem):
-      addFloatRoundtrip(result, x)
-    else:
+    when defined(nimLegacySprintf):
       addFloatSprintf(result, x)
+    else:
+      addFloatRoundtrip(result, x)
   when defined(js):
     when nimvm: impl()
     else:

testament/important_packages.nim

@@ -61,7 +61,7 @@ pkg "comprehension", "nimble test", "https://github.com/alehander92/comprehensio
 pkg "constantine", "nimble make_lib"
 pkg "cowstrings"
 pkg "criterion", allowFailure = true # needs testing binary
-pkg "datamancer"
+pkg "datamancer", url = "https://github.com/nim-lang/Datamancer"
 pkg "dashing", "nim c tests/functional.nim"
 pkg "delaunay"
 pkg "dnsclient", allowFailure = true # super fragile

tests/config.nims

@@ -35,7 +35,6 @@ hint("Processing", off)
 switch("define", "nimExperimentalLinenoiseExtra")
 
 # preview APIs are expected to be the new default in upcoming versions
-switch("define", "nimPreviewFloatRoundtrip")
 #switch("define", "nimPreviewDotLikeOps") # deprecated?
 switch("define", "nimPreviewJsonutilsHoleyEnum")
 switch("define", "nimPreviewHashRef")

tests/float/tfloats.nim

@@ -1,5 +1,4 @@
 discard """
-  matrix: "-d:nimPreviewFloatRoundtrip; -u:nimPreviewFloatRoundtrip"
   targets: "c cpp js"
 """
 
@@ -66,29 +65,18 @@ template main =
     block: # example 1
       let a = 0.1+0.2
       doAssert a != 0.3
-      when defined(nimPreviewFloatRoundtrip):
-        doAssert $a == "0.30000000000000004"
-      else:
-        whenRuntimeJs: discard
-        do: doAssert $a == "0.3"
+      doAssert $a == "0.30000000000000004"
     block: # example 2
       const a = 0.1+0.2
-      when defined(nimPreviewFloatRoundtrip):
-        doAssert $($a, a) == """("0.30000000000000004", 0.30000000000000004)"""
-      else:
-        whenRuntimeJs: discard
-        do: doAssert $($a, a) == """("0.3", 0.3)"""
+      doAssert $($a, a) == """("0.30000000000000004", 0.30000000000000004)"""
     block: # example 3
       const a1 = 0.1+0.2
       let a2 = a1
       doAssert a1 != 0.3
-      when defined(nimPreviewFloatRoundtrip):
-        doAssert $[$a1, $a2] == """["0.30000000000000004", "0.30000000000000004"]"""
-      else:
-        whenRuntimeJs: discard
-        do: doAssert $[$a1, $a2] == """["0.3", "0.3"]"""
+      doAssert $[$a1, $a2] == """["0.30000000000000004", "0.30000000000000004"]"""
 
-  when defined(nimPreviewFloatRoundtrip):
+
+  when true:
     block: # bug #18148
       var a = 1.1'f32
       doAssert $a == "1.1", $a # was failing