From a5f4bc3fe04f697c1077d70e6c44fee2b7571c9e Mon Sep 17 00:00:00 2001
From: "Paul \"LeoNerd\" Evans" <leonerd@leonerd.org.uk>
Date: Mon, 22 Jan 2024 22:29:39 +0000
Subject: [PATCH] Add builtin::inf and builtin::nan

---
 builtin.c      | 29 +++++++++++++++++++++++++++++
 lib/builtin.pm | 19 ++++++++++++++++++-
 lib/builtin.t  | 12 ++++++++++++
 3 files changed, 59 insertions(+), 1 deletion(-)

diff --git a/builtin.c b/builtin.c
index 415c84d00d27c..4dcb2d41e2808 100644
--- a/builtin.c
+++ b/builtin.c
@@ -87,15 +87,40 @@ XS(XS_builtin_false)
     XSRETURN_NO;
 }
 
+XS(XS_builtin_inf);
+XS(XS_builtin_inf)
+{
+    dXSARGS;
+    if(items)
+        croak_xs_usage(cv, "");
+    mPUSHn(PL_inf.nv);
+    XSRETURN(1);
+}
+
+XS(XS_builtin_nan);
+XS(XS_builtin_nan)
+{
+    dXSARGS;
+    if(items)
+        croak_xs_usage(cv, "");
+    mPUSHn(PL_nan.nv);
+    XSRETURN(1);
+}
+
 enum {
     BUILTIN_CONST_FALSE,
     BUILTIN_CONST_TRUE,
+    BUILTIN_CONST_INF,
+    BUILTIN_CONST_NAN,
 };
 
 static OP *ck_builtin_const(pTHX_ OP *entersubop, GV *namegv, SV *ckobj)
 {
     const struct BuiltinFuncDescriptor *builtin = NUM2PTR(const struct BuiltinFuncDescriptor *, SvUV(ckobj));
 
+    if(builtin->is_experimental)
+        warn_experimental_builtin(builtin->name);
+
     SV *prototype = newSVpvs("");
     SAVEFREESV(prototype);
 
@@ -107,6 +132,8 @@ static OP *ck_builtin_const(pTHX_ OP *entersubop, GV *namegv, SV *ckobj)
     switch(builtin->ckval) {
         case BUILTIN_CONST_FALSE: constval = &PL_sv_no; break;
         case BUILTIN_CONST_TRUE:  constval = &PL_sv_yes; break;
+        case BUILTIN_CONST_INF:   constval = newSVnv(PL_inf.nv); break;
+        case BUILTIN_CONST_NAN:   constval = newSVnv(PL_nan.nv); break;
         default:
             DIE(aTHX_ "panic: unrecognised builtin_const value %" IVdf,
                       builtin->ckval);
@@ -516,6 +543,8 @@ static const struct BuiltinFuncDescriptor builtins[] = {
     /* constants */
     { "true",  SHORTVER(5,39), &XS_builtin_true,   &ck_builtin_const, BUILTIN_CONST_TRUE,  false },
     { "false", SHORTVER(5,39), &XS_builtin_false,  &ck_builtin_const, BUILTIN_CONST_FALSE, false },
+    { "inf",        NO_BUNDLE, &XS_builtin_inf,    &ck_builtin_const, BUILTIN_CONST_INF,   true },
+    { "nan",        NO_BUNDLE, &XS_builtin_nan,    &ck_builtin_const, BUILTIN_CONST_NAN,   true },
 
     /* unary functions */
     { "is_bool",         NO_BUNDLE, &XS_builtin_func1_scalar, &ck_builtin_func1, OP_IS_BOOL,    true  },
diff --git a/lib/builtin.pm b/lib/builtin.pm
index 7bf8d6d67ee0f..6863a4aabbe47 100644
--- a/lib/builtin.pm
+++ b/lib/builtin.pm
@@ -1,4 +1,4 @@
-package builtin 0.012;
+package builtin 0.013;
 
 use strict;
 use warnings;
@@ -18,6 +18,7 @@ builtin - Perl pragma to import built-in utility functions
 
     use builtin qw(
         true false is_bool
+        inf nan
         weaken unweaken is_weak
         blessed refaddr reftype
         created_as_string created_as_number
@@ -143,6 +144,22 @@ or any variable containing one of these results.
 This function used to be named C<isbool>. A compatibility alias is provided
 currently but will be removed in a later version.
 
+=head2 inf
+
+    $num = inf;
+
+This function is currently B<experimental>.
+
+Returns the numerical infinity value.
+
+=head2 nan
+
+    $num = nan;
+
+This function is currently B<experimental>.
+
+Returns the numerical not-a-number value.
+
 =head2 weaken
 
     weaken($ref);
diff --git a/lib/builtin.t b/lib/builtin.t
index 391c4c72a0f47..532bf2902342d 100644
--- a/lib/builtin.t
+++ b/lib/builtin.t
@@ -51,6 +51,18 @@ package FetchStoreCounter {
     is(prototype(\&builtin::is_bool), '$', 'is_bool prototype');
 }
 
+# float constants
+{
+    use builtin qw( inf nan );
+
+    ok(inf, 'inf is true');
+    ok(inf > 1E10, 'inf is bigger than 1E10');
+    ok(inf == inf, 'inf is equal to inf');
+    ok(inf == inf + 1, 'inf is equal to inf + 1');
+
+    ok(nan != nan, 'NaN is not equal to NaN');
+}
+
 # weakrefs
 {
     use builtin qw( is_weak weaken unweaken );