From 248f4800febc14e360aa7cf9952d998bb719a679 Mon Sep 17 00:00:00 2001
From: Antonio Rojas <arojas@archlinux.org>
Date: Sun, 6 Oct 2024 22:50:27 +0200
Subject: [PATCH] Restore prec_words_to_bits (renamed to prec_pari_to_bits) for
 backwards compatibility

---
 cypari2/pari_instance.pxd |  1 +
 cypari2/pari_instance.pyx | 19 +++++++++++++++++++
 2 files changed, 20 insertions(+)

diff --git a/cypari2/pari_instance.pxd b/cypari2/pari_instance.pxd
index 528db5c..2dccd47 100644
--- a/cypari2/pari_instance.pxd
+++ b/cypari2/pari_instance.pxd
@@ -4,6 +4,7 @@ cimport cython
 from .gen cimport Gen
 
 cpdef long prec_bits_to_pari(unsigned long prec_in_bits) noexcept
+cpdef long prec_pari_to_bits(long prec_pari) noexcept
 cpdef long default_bitprec() noexcept
 
 cdef class Pari_auto:
diff --git a/cypari2/pari_instance.pyx b/cypari2/pari_instance.pyx
index 43ee3c7..4227919 100644
--- a/cypari2/pari_instance.pyx
+++ b/cypari2/pari_instance.pyx
@@ -366,6 +366,25 @@ cpdef long prec_bits_to_pari(unsigned long prec_in_bits) noexcept:
     return nbits2prec(prec_in_bits)
 
 
+cpdef long prec_pari_to_bits(long prec_pari) noexcept:
+    r"""
+    Convert from pari real precision to precision
+    expressed in bits. Note: this adjusts for the two codewords of a
+    pari real, and is architecture-dependent.
+    Examples:
+    >>> from cypari2.pari_instance import prec_words_to_bits
+    >>> import sys
+    >>> bitness = '64' if sys.maxsize > (1 << 32) else '32'
+    >>> prec_words_to_bits(10) == (256 if bitness == '32' else 512)
+    True
+    >>> ans32 = [(3, 32), (4, 64), (5, 96), (6, 128), (7, 160), (8, 192), (9, 224)]
+    >>> ans64 = [(3, 64), (4, 128), (5, 192), (6, 256), (7, 320), (8, 384), (9, 448)] # 64-bit
+    >>> [(n, prec_words_to_bits(n)) for n in range(3, 10)] == (ans32 if bitness == '32' else ans64)
+    True
+    """
+    return prec2nbits(prec_pari)
+
+
 cpdef long default_bitprec() noexcept:
     r"""
     Return the default precision in bits.