Get back to basics, with some basic tests working.

generation/src/Conversions.hs

@@ -0,0 +1,98 @@
+module Conversions(
+    conversions
+  )
+ where
+
+import Data.List(intercalate)
+import File
+import Gen
+
+conversions :: File
+conversions = File {
+  predicate = \ _ _ -> True,
+  outputName = "conversions",
+  generator = declareConversions
+}
+
+declareConversions :: Word -> Gen ()
+declareConversions bitsize =
+  do let name = "U" ++ show bitsize
+         entries = bitsize `div` 64
+     out "use core::convert::{From,TryFrom};"
+     out "#[cfg(test)]"
+     out "use quickcheck::quickcheck;"
+     out ("use super::" ++ name ++ ";")
+     blank
+     buildUnsignedPrimConversions name entries "u8"    >> blank
+     buildUnsignedPrimConversions name entries "u16"   >> blank
+     buildUnsignedPrimConversions name entries "u32"   >> blank
+     buildUnsignedPrimConversions name entries "u64"   >> blank
+     buildUnsignedPrimConversions name entries "usize" >> blank
+     buildSignedPrimConversions   name entries "i8"    >> blank
+     buildSignedPrimConversions   name entries "i16"   >> blank
+     buildSignedPrimConversions   name entries "i32"   >> blank
+     buildSignedPrimConversions   name entries "i64"   >> blank
+     buildSignedPrimConversions   name entries "isize"
+     blank
+     out ("#[cfg(test)]")
+     wrapIndent "quickcheck!" $
+       do roundTripTest name "u8"     >> blank
+          roundTripTest name "u16"    >> blank
+          roundTripTest name "u32"    >> blank
+          roundTripTest name "u64"    >> blank
+          roundTripTest name "usize"
+
+buildUnsignedPrimConversions :: String -> Word -> String -> Gen ()
+buildUnsignedPrimConversions name entries primtype =
+  do implFor ("From<" ++ primtype ++ ">") name $
+       wrapIndent ("fn from(x: " ++ primtype ++ ") -> Self") $
+         do let zeroes = replicate (fromIntegral (entries - 1)) "0,"
+                values =  ("x as u64," : zeroes)
+            out (name ++ " { value: [ ")
+            indent $ printBy 8 values
+            out ("] }")
+     blank
+     implFor ("From<" ++ name ++ ">") primtype $
+       wrapIndent ("fn from(x: " ++ name ++ ") -> Self") $
+         out ("x.value[0] as " ++ primtype)
+     blank
+     implFor' ("From<&'a " ++ name ++ ">") primtype $
+       wrapIndent ("fn from(x: &" ++ name ++ ") -> Self") $
+         out ("x.value[0] as " ++ primtype)
+
+buildSignedPrimConversions :: String -> Word -> String -> Gen ()
+buildSignedPrimConversions name entries primtype =
+  do implFor ("TryFrom<" ++ primtype ++ ">") name $
+       do out ("type Error = &'static str;")
+          blank
+          wrapIndent ("fn try_from(x: " ++ primtype ++ ") -> Result<Self,Self::Error>") $
+            do wrapIndent ("if x < 0") $
+                 out ("return Err(\"Attempt to convert negative number to " ++
+                      name ++ ".\");")
+               blank
+               let zeroes = replicate (fromIntegral (entries - 1)) "0,"
+                   values =  ("x as u64," : zeroes)
+               out ("Ok(" ++ name ++ " { value: [ ")
+               indent $ printBy 8 values
+               out ("] })")
+     blank
+     implFor ("From<" ++ name ++ ">") primtype $
+       wrapIndent ("fn from(x: " ++ name ++ ") -> Self") $
+         out ("x.value[0] as " ++ primtype)
+     blank
+     implFor' ("From<&'a " ++ name ++ ">") primtype $
+       wrapIndent ("fn from(x: &" ++ name ++ ") -> Self") $
+         out ("x.value[0] as " ++ primtype)
+
+roundTripTest :: String -> String -> Gen ()
+roundTripTest name primtype =
+  wrapIndent ("fn " ++ primtype ++ "_roundtrips(x: " ++ primtype ++ ") -> bool") $
+    do out ("let big = " ++ name ++ "::from(x);");
+       out ("let small = " ++ primtype ++ "::from(big);")
+       out ("x == small")
+
+printBy :: Int -> [String] -> Gen ()
+printBy amt xs
+  | length xs <= amt = out (intercalate " " xs)
+  | otherwise        = printBy amt (take amt xs) >>
+                       printBy amt (drop amt xs)