From 171d80ac1e5bd006c2c600f36a42440dfb635605 Mon Sep 17 00:00:00 2001
From: Bruce Hill <bruce@bruce-hill.com>
Date: Fri, 18 Apr 2025 15:52:21 -0400
Subject: Make Int.prev_prime() optional instead of erroring

---
 src/environment.c     | 2 +-
 src/stdlib/integers.c | 4 ++--
 src/stdlib/integers.h | 2 +-
 3 files changed, 4 insertions(+), 4 deletions(-)

(limited to 'src')

diff --git a/src/environment.c b/src/environment.c
index 35c76fe5..651bc9ca 100644
--- a/src/environment.c
+++ b/src/environment.c
@@ -121,7 +121,7 @@ env_t *global_env(bool source_mapping)
             {"power", "Int$power", "func(base:Int,exponent:Int -> Int)"},
 #if __GNU_MP_VERSION >= 6
 #if __GNU_MP_VERSION_MINOR >= 3
-            {"prev_prime", "Int$prev_prime", "func(x:Int -> Int)"},
+            {"prev_prime", "Int$prev_prime", "func(x:Int -> Int?)"},
 #endif
 #endif
             {"right_shifted", "Int$right_shifted", "func(x,y:Int -> Int)"},
diff --git a/src/stdlib/integers.c b/src/stdlib/integers.c
index b4ca69d3..bb39d99c 100644
--- a/src/stdlib/integers.c
+++ b/src/stdlib/integers.c
@@ -434,12 +434,12 @@ public Int_t Int$next_prime(Int_t x)
 
 #if __GNU_MP_VERSION >= 6
 #if __GNU_MP_VERSION_MINOR >= 3
-public Int_t Int$prev_prime(Int_t x)
+public OptionalInt_t Int$prev_prime(Int_t x)
 {
     mpz_t p;
     mpz_init_set_int(p, x);
     if (unlikely(mpz_prevprime(p, p) == 0))
-        fail("There is no prime number before ", x);
+        return NONE_INT;
     return Int$from_mpz(p);
 }
 #endif
diff --git a/src/stdlib/integers.h b/src/stdlib/integers.h
index c7643a8d..7b7cf12e 100644
--- a/src/stdlib/integers.h
+++ b/src/stdlib/integers.h
@@ -144,7 +144,7 @@ bool Int$is_prime(Int_t x, Int_t reps);
 Int_t Int$next_prime(Int_t x);
 #if __GNU_MP_VERSION >= 6
 #if __GNU_MP_VERSION_MINOR >= 3
-Int_t Int$prev_prime(Int_t x);
+OptionalInt_t Int$prev_prime(Int_t x);
 #endif
 #endif
 Int_t Int$choose(Int_t n, Int_t k);
-- 
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