Add some misc fuzzers

lib/aiken/fuzz.ak

@@ -1,5 +1,8 @@
 use aiken/builtin
+use aiken/bytearray
+use aiken/hash.{blake2b_256}
 use aiken/list
+use aiken/math
 
 // Internal
 
@@ -95,11 +98,12 @@ pub fn bool() -> Fuzzer<Bool> {
 }
 
 pub fn bytearray() -> Fuzzer<ByteArray> {
-  fail
+  bytearray_between(0, 1024)
 }
 
-pub fn bytearray_between(_min: Int, _max: Int) -> Fuzzer<ByteArray> {
-  fail
+pub fn bytearray_between(min: Int, max: Int) -> Fuzzer<ByteArray> {
+  let bytes <- and_then(list_between(byte(), min, max))
+  constant(list.foldl(bytes, #"", bytearray.concat))
 }
 
 /// Generate a random integer value. It favors small values near zero, but generate across the whole range [-2^64; 2^64 - 1]
@@ -113,33 +117,33 @@ pub fn int() -> Fuzzer<Int> {
           Some((Seeded { seed: builtin.blake2b_256(seed), choices }, choice))
         }
           |> fn(return) {
-               if fst_choice < 128 {
-                 return(fst_choice, builtin.cons_bytearray(fst_choice, choices))
-               } else if fst_choice < 224 {
-                 return(
-                   fst_choice % 16,
-                   builtin.cons_bytearray(fst_choice % 16, choices),
-                 )
-               } else if fst_choice < 236 {
-                 let snd_choice = builtin.index_bytearray(seed, 1)
-                 return(
-                   -snd_choice,
-                   builtin.cons_bytearray(
-                     snd_choice,
-                     builtin.cons_bytearray(fst_choice, choices),
-                   ),
-                 )
-               } else {
-                 let snd_choice = builtin.index_bytearray(seed, 1)
-                 return(
-                   u16(fst_choice, snd_choice),
-                   builtin.cons_bytearray(
-                     snd_choice,
-                     builtin.cons_bytearray(fst_choice, choices),
-                   ),
-                 )
-               }
-             }
+              if fst_choice < 128 {
+                return(fst_choice, builtin.cons_bytearray(fst_choice, choices))
+              } else if fst_choice < 224 {
+                return(
+                  fst_choice % 16,
+                  builtin.cons_bytearray(fst_choice % 16, choices),
+                )
+              } else if fst_choice < 236 {
+                let snd_choice = builtin.index_bytearray(seed, 1)
+                return(
+                  -snd_choice,
+                  builtin.cons_bytearray(
+                    snd_choice,
+                    builtin.cons_bytearray(fst_choice, choices),
+                  ),
+                )
+              } else {
+                let snd_choice = builtin.index_bytearray(seed, 1)
+                return(
+                  u16(fst_choice, snd_choice),
+                  builtin.cons_bytearray(
+                    snd_choice,
+                    builtin.cons_bytearray(fst_choice, choices),
+                  ),
+                )
+              }
+            }
       }
 
       Replayed { cursor, choices } ->
@@ -166,6 +170,18 @@ pub fn int() -> Fuzzer<Int> {
   }
 }
 
+pub fn positive_int() -> Fuzzer<Int> {
+  int() |> map(math.abs) |> map(fn(x) { x + 1 })
+}
+
+pub fn nonnegative_int() -> Fuzzer<Int> {
+  int() |> map(math.abs)
+}
+
+pub fn negative_int() -> Fuzzer<Int> {
+  int() |> map(fn(x) { -math.abs(x + 1) })
+}
+
 pub fn int_between(min: Int, max: Int) -> Fuzzer<Int> {
   if max < min {
     int_between(max, min)
@@ -176,19 +192,117 @@ pub fn int_between(min: Int, max: Int) -> Fuzzer<Int> {
     let delta = ( max - min ) / 2
     int()
       |> and_then(
-           fn(lo) {
-             int()
-               |> map(fn(hi) { mid - lo % ( delta + 1 ) + hi % ( delta + 1 ) })
-           },
-         )
+          fn(lo) {
+            int()
+              |> map(fn(hi) { mid - lo % ( delta + 1 ) + hi % ( delta + 1 ) })
+          },
+        )
   }
 }
 
+pub fn uniform(bits: Int) -> Fuzzer<Int> {
+  // TODO: switch to Han-Hoshi for better uniform, and support min/max?
+  if bits == 0 {
+    constant(0)
+  } else {
+    let bit <- and_then(bool())
+    let rest <- and_then(uniform(bits - 1))
+    if bit {
+      constant(rest * 2 + 1)
+    } else {
+      constant(rest * 2)
+    }
+  }
+}
+
+pub fn byte() -> Fuzzer<ByteArray> {
+  let byte <- and_then(int_between(0, 255))
+  constant(bytearray.push(#"", byte))
+}
+
+pub fn hash() -> Fuzzer<ByteArray> {
+  let b <- and_then(byte())
+  let hash = blake2b_256(b)
+  constant(bytearray.take(hash, 28))
+}
+
 /// Generate a random list of elements from a given element.
 pub fn list(fuzzer: Fuzzer<a>) -> Fuzzer<List<a>> {
   list_between(fuzzer, 0, 32)
 }
 
+pub fn nonempty_list(fuzzer: Fuzzer<a>) -> Fuzzer<List<a>> {
+  list_between(fuzzer, 1, 32)
+}
+
+pub fn sorted(
+  fuzzer: Fuzzer<List<a>>,
+  compare: fn(a, a) -> Ordering,
+) -> Fuzzer<List<a>> {
+  let ls <- and_then(fuzzer)
+  constant(list.sort(ls, compare))
+}
+
+pub fn list_with_elem(fuzzer: Fuzzer<a>) -> Fuzzer<(List<a>, a)> {
+  let xs <- and_then(nonempty_list(fuzzer))
+  let x <- and_then(one_of(xs))
+  constant((xs, x))
+}
+
+pub fn list_with_subset(fuzzer: Fuzzer<a>) -> Fuzzer<(List<a>, List<a>)> {
+  let xs <- and_then(list(fuzzer))
+  let bits <- and_then(list_between(bool(), 0, list.length(xs)))
+  let ys =
+    list.filter(
+      list.zip(xs, bits),
+      fn(pair) {
+        let (_, b) = pair
+        b
+      },
+    )
+  let (ys, _) = list.unzip(ys)
+  constant((xs, ys))
+}
+
+pub fn filter(fuzzer: Fuzzer<a>, predicate: fn(a) -> Bool) -> Fuzzer<a> {
+  do_filter(fuzzer, predicate, 100)
+}
+
+fn do_filter(
+  fuzzer: Fuzzer<a>,
+  predicate: fn(a) -> Bool,
+  max_tries: Int,
+) -> Fuzzer<a> {
+  if max_tries <= 0 {
+    fail
+  } else {
+    let x <- and_then(fuzzer)
+    if predicate(x) {
+      constant(x)
+    } else {
+      do_filter(fuzzer, predicate, max_tries - 1)
+    }
+  }
+}
+
+pub fn distinct(fuzzer: Fuzzer<List<a>>) -> Fuzzer<List<a>> {
+  let xs <- and_then(fuzzer)
+  constant(dedup(xs, []))
+}
+
+fn dedup(xs: List<a>, seen: List<a>) -> List<a> {
+  when xs is {
+    [] ->
+      []
+    [x, ..xs] ->
+      if list.has(seen, x) {
+        dedup(xs, seen)
+      } else {
+        [x, ..dedup(xs, [x, ..seen])]
+      }
+  }
+}
+
 /// Generate a random list of elements with length within specified bounds.
 pub fn list_between(fuzzer: Fuzzer<a>, min: Int, max: Int) -> Fuzzer<List<a>> {
   if min > max {
@@ -212,38 +326,38 @@ fn do_list_between(avg, fuzzer, min, max, length, xs) -> Fuzzer<List<a>> {
     with_choice(min_rand)
       |> and_then(always(fuzzer, _))
       |> and_then(
-           fn(x) {
-             do_list_between(avg, fuzzer, min, max, length + 1, [x, ..xs])
-           },
-         )
+          fn(x) {
+            do_list_between(avg, fuzzer, min, max, length + 1, [x, ..xs])
+          },
+        )
   } else if length >= max {
     with_choice(max_rand)
       |> map(fn(_) { xs })
   } else {
     rand
       |> and_then(
-           fn(n) {
-             // This is the probability above but simplified to use only
-             // multiplications since division on-chain is expensive.
-             if n + n * avg <= max_rand * avg {
-               fuzzer
-                 |> and_then(
-                      fn(x) {
-                        do_list_between(
-                          avg,
-                          fuzzer,
-                          min,
-                          max,
-                          length + 1,
-                          [x, ..xs],
-                        )
-                      },
-                    )
-             } else {
-               constant(xs)
-             }
-           },
-         )
+          fn(n) {
+            // This is the probability above but simplified to use only
+            // multiplications since division on-chain is expensive.
+            if n + n * avg <= max_rand * avg {
+              fuzzer
+                |> and_then(
+                    fn(x) {
+                      do_list_between(
+                        avg,
+                        fuzzer,
+                        min,
+                        max,
+                        length + 1,
+                        [x, ..xs],
+                      )
+                    },
+                  )
+            } else {
+              constant(xs)
+            }
+          },
+        )
   }
 }
 
@@ -253,32 +367,55 @@ fn do_list_between(avg, fuzzer, min, max, length, xs) -> Fuzzer<List<a>> {
 pub fn one_of(xs: List<a>) -> Fuzzer<a> {
   let len = list.length(xs)
   expect len > 0
-  int_between(0, len - 1)
+  uniform(math.log(len, 2) + 1)
     |> map(
-         fn(ix: Int) {
-           expect Some(item) = list.at(xs, ix)
-           item
-         },
-       )
+        fn(ix: Int) {
+          expect Some(item) = list.at(xs, ix % len)
+          item
+        },
+      )
 }
 
 // Combining Fuzzers
 
-pub fn either(_fuzz_a: Fuzzer<a>, _fuzz_b: Fuzzer<a>) -> Fuzzer<a> {
-  fail
+pub fn either(fuzz_a: Fuzzer<a>, fuzz_b: Fuzzer<a>) -> Fuzzer<a> {
+  bool()
+    |> and_then(
+        fn(b) {
+          if b {
+            fuzz_a
+          } else {
+            fuzz_b
+          }
+        },
+      )
+}
+
+pub fn ordered_pair(
+  fuzz_a: Fuzzer<a>,
+  fuzz_b: Fuzzer<a>,
+  compare: fn(a, a) -> Ordering,
+) -> Fuzzer<(a, a)> {
+  let a <- and_then(fuzz_a)
+  let b <- and_then(fuzz_b)
+  if compare(a, b) == Greater {
+    constant((b, a))
+  } else {
+    constant((a, b))
+  }
 }
 
 pub fn option(fuzz_a: Fuzzer<a>) -> Fuzzer<Option<a>> {
   bool()
     |> and_then(
-         fn(predicate) {
-           if predicate {
-             fuzz_a |> map(Some)
-           } else {
-             constant(None)
-           }
-         },
-       )
+        fn(predicate) {
+          if predicate {
+            fuzz_a |> map(Some)
+          } else {
+            constant(None)
+          }
+        },
+      )
 }
 
 /// Combine a [Fuzzer](https://aiken-lang.github.io/prelude/aiken.html#Fuzzer) with the result of a another one.
@@ -608,6 +745,6 @@ pub fn map9(
 
 pub fn label(str: String) -> Void {
   str
-    |> builtin.append_string(@"", _)
+    |> builtin.append_string(@"\0", _)
     |> builtin.debug(Void)
 }