bug#74031: [PATCH v2] srfi-64: Accept complex numbers in test-approximate.

[Tomas Volf <~@wolfsden.cz>]

The specification mandates reals, but the reference implementation
supports complex numbers.  So as implementation extension, support them
as well.

* module/srfi/srfi-64.scm (within-epsilon): Support complex arguments.
---
Require error to be real number and check using (checks notes) Chebyshev
distance.

 module/srfi/srfi-64.scm | 14 ++++++++++++--
 1 file changed, 12 insertions(+), 2 deletions(-)

diff --git a/module/srfi/srfi-64.scm b/module/srfi/srfi-64.scm
index 1f60a72e5..453296364 100644
--- a/module/srfi/srfi-64.scm
+++ b/module/srfi/srfi-64.scm
@@ -776,8 +776,14 @@ Test whether result of @var{test-expr} matches @var{expected} using

 (define (within-epsilon ε)
   (λ (expected actual)
-    (and (>= actual (- expected ε))
-         (<= actual (+ expected ε)))))
+    (let ((e-r (real-part expected))
+          (e-i (imag-part expected))
+          (a-r (real-part actual))
+          (a-i (imag-part actual)))
+      (and (>= a-r (- e-r ε))
+           (<= a-r (+ e-r ε))
+           (>= a-i (- e-i ε))
+           (<= a-i (+ e-i ε))))))

 (define-syntax %test-approximate
   (λ (x)
@@ -808,6 +814,10 @@ Test whether result of @var{test-expr} matches @var{expected} using
 Test whether result of @var{test-expr} is within @var{error} of
 @var{expected}.

+As implementation extension, complex numbers are supported as well.  It tests
+whether real parts are within @code{(real-part @var{error})}, and imaginary
+parts within @code{(imag-part @var{error})}.
+
 @end defspec")

 (define-syntax %test-error
--
2.46.0