Add Nat to initial ghci environment for lols

1 files changed, 19 insertions, 0 deletions

diff --git a/bwrap-files/workdir/initdefs.hs b/bwrap-files/workdir/initdefs.hs
new file mode 100644
index 0000000..7083fe0
--- /dev/null
+++ b/bwrap-files/workdir/initdefs.hs
@@ -0,0 +1,19 @@
+:{
+data Nat = Z | S Nat deriving (Show, Eq, Ord)
+
+instance Num Nat where
+  Z + n = n
+  S m + n = S (m + n)
+  Z * _ = Z
+  S m * n = n + m * n
+  negate _ = error "negate on Nat"
+  abs = id
+  signum Z = Z
+  signum _ = 1
+  fromInteger n
+    | n < 0 = error "fromInteger to Nat on negative number"
+    | otherwise =
+        let go 0 = Z
+            go m = S (go (m-1))
+        in go n
+:}