|
| 1 | +---- MODULE LambdaOP ---- |
| 2 | +EXTENDS Naturals, Sequences, TLC |
| 3 | + |
| 4 | +CONSTANT MaxDepth |
| 5 | + |
| 6 | +VARIABLE evalStack, depth, currentOp |
| 7 | + |
| 8 | +ToNumber(churchNumeral) == |
| 9 | + CASE churchNumeral.type = "ChurchNumeral" -> churchNumeral.value |
| 10 | + [] OTHER -> 0 |
| 11 | + |
| 12 | +Max(a, b) == IF a > b THEN a ELSE b |
| 13 | + |
| 14 | +(* Basic Lambda Calculus *) |
| 15 | +Variable(name) == [type |-> "Variable", value |-> name, left |-> [type |-> "", value |-> ""], right |-> [type |-> "", value |-> ""]] |
| 16 | + |
| 17 | +Abstraction(param, body) == [type |-> "Abstraction", value |-> "lambda", left |-> Variable(param), right |-> body] |
| 18 | + |
| 19 | +Application(func, arg) == [type |-> "Application", value |-> "apply", left |-> func, right |-> arg] |
| 20 | + |
| 21 | +(* Church Numerals *) |
| 22 | +ChurchNumeral(n) == |
| 23 | + [type |-> "ChurchNumeral", |
| 24 | + value |-> n, |
| 25 | + left |-> [type |-> "", value |-> ""], |
| 26 | + right |-> [type |-> "", value |-> ""]] |
| 27 | + |
| 28 | +Succ == |
| 29 | + [type |-> "Builtin", value |-> "succ", |
| 30 | + left |-> [type |-> "", value |-> ""], |
| 31 | + right |-> [type |-> "", value |-> ""]] |
| 32 | + |
| 33 | +Pred == |
| 34 | + [type |-> "Builtin", value |-> "pred", |
| 35 | + left |-> [type |-> "", value |-> ""], |
| 36 | + right |-> [type |-> "", value |-> ""]] |
| 37 | + |
| 38 | +IsZero == |
| 39 | + [type |-> "Builtin", value |-> "is_zero", |
| 40 | + left |-> [type |-> "", value |-> ""], |
| 41 | + right |-> [type |-> "", value |-> ""]] |
| 42 | + |
| 43 | +Multiply == |
| 44 | + [type |-> "Builtin", value |-> "multiply", |
| 45 | + left |-> [type |-> "", value |-> ""], |
| 46 | + right |-> [type |-> "", value |-> ""]] |
| 47 | + |
| 48 | +(* Church Booleans *) |
| 49 | +ChurchTrue == |
| 50 | + Abstraction("x", Abstraction("y", Variable("x"))) |
| 51 | + |
| 52 | +ChurchFalse == |
| 53 | + Abstraction("x", Abstraction("y", Variable("y"))) |
| 54 | + |
| 55 | +And == |
| 56 | + [type |-> "Builtin", value |-> "and", |
| 57 | + left |-> [type |-> "", value |-> ""], |
| 58 | + right |-> [type |-> "", value |-> ""]] |
| 59 | + |
| 60 | +Or == |
| 61 | + [type |-> "Builtin", value |-> "or", |
| 62 | + left |-> [type |-> "", value |-> ""], |
| 63 | + right |-> [type |-> "", value |-> ""]] |
| 64 | + |
| 65 | +Not == |
| 66 | + [type |-> "Builtin", value |-> "not", |
| 67 | + left |-> [type |-> "", value |-> ""], |
| 68 | + right |-> [type |-> "", value |-> ""]] |
| 69 | + |
| 70 | +(* Control Flow *) |
| 71 | +IfThenElse == |
| 72 | + [type |-> "Builtin", value |-> "ifthenelse", |
| 73 | + left |-> [type |-> "", value |-> ""], |
| 74 | + right |-> [type |-> "", value |-> ""]] |
| 75 | + |
| 76 | +(* Pairs *) |
| 77 | +Pair == |
| 78 | + [type |-> "Builtin", value |-> "pair", |
| 79 | + left |-> [type |-> "", value |-> ""], |
| 80 | + right |-> [type |-> "", value |-> ""]] |
| 81 | + |
| 82 | +First == |
| 83 | + [type |-> "Builtin", value |-> "first", |
| 84 | + left |-> [type |-> "", value |-> ""], |
| 85 | + right |-> [type |-> "", value |-> ""]] |
| 86 | + |
| 87 | +Second == |
| 88 | + [type |-> "Builtin", value |-> "second", |
| 89 | + left |-> [type |-> "", value |-> ""], |
| 90 | + right |-> [type |-> "", value |-> ""]] |
| 91 | + |
| 92 | +(* Recursion *) |
| 93 | +YCombinator == |
| 94 | + [type |-> "Builtin", value |-> "Y", |
| 95 | + left |-> [type |-> "", value |-> ""], |
| 96 | + right |-> [type |-> "", value |-> ""]] |
| 97 | + |
| 98 | +EvalSucc == |
| 99 | + /\ Len(evalStack) > 0 |
| 100 | + /\ depth < MaxDepth |
| 101 | + /\ LET n == Head(evalStack) |
| 102 | + IN /\ evalStack' = Tail(evalStack) \o <<ChurchNumeral(ToNumber(n) + 1)>> |
| 103 | + /\ depth' = depth + 1 |
| 104 | + |
| 105 | +EvalPred == |
| 106 | + /\ Len(evalStack) > 0 |
| 107 | + /\ depth < MaxDepth |
| 108 | + /\ LET n == Head(evalStack) |
| 109 | + IN /\ evalStack' = Tail(evalStack) \o <<ChurchNumeral(Max(0, ToNumber(n) - 1))>> |
| 110 | + /\ depth' = depth + 1 |
| 111 | + |
| 112 | +EvalIsZero == |
| 113 | + /\ Len(evalStack) > 0 |
| 114 | + /\ LET n == Head(evalStack) |
| 115 | + IN /\ evalStack' = Tail(evalStack) \o <<IF ToNumber(n) = 0 THEN ChurchTrue ELSE ChurchFalse>> |
| 116 | + /\ depth' = depth + 1 |
| 117 | + |
| 118 | +EvalMultiply == |
| 119 | + /\ Len(evalStack) > 1 |
| 120 | + /\ depth < MaxDepth |
| 121 | + /\ LET n == Head(evalStack) |
| 122 | + m == Head(Tail(evalStack)) |
| 123 | + IN /\ evalStack' = Tail(Tail(evalStack)) \o <<ChurchNumeral(ToNumber(n) * ToNumber(m))>> |
| 124 | + /\ depth' = depth + 1 |
| 125 | + |
| 126 | +EvalAnd == |
| 127 | + /\ Len(evalStack) > 1 |
| 128 | + /\ LET b1 == Head(evalStack) |
| 129 | + b2 == Head(Tail(evalStack)) |
| 130 | + IN /\ evalStack' = Tail(Tail(evalStack)) \o <<IF b1 = ChurchTrue /\ b2 = ChurchTrue THEN ChurchTrue ELSE ChurchFalse>> |
| 131 | + /\ depth' = depth + 1 |
| 132 | + |
| 133 | +EvalOr == |
| 134 | + /\ Len(evalStack) > 1 |
| 135 | + /\ LET b1 == Head(evalStack) |
| 136 | + b2 == Head(Tail(evalStack)) |
| 137 | + IN /\ evalStack' = Tail(Tail(evalStack)) \o <<IF b1 = ChurchTrue \/ b2 = ChurchTrue THEN ChurchTrue ELSE ChurchFalse>> |
| 138 | + /\ depth' = depth + 1 |
| 139 | + |
| 140 | +EvalNot == |
| 141 | + /\ Len(evalStack) > 0 |
| 142 | + /\ LET b == Head(evalStack) |
| 143 | + IN /\ evalStack' = Tail(evalStack) \o <<IF b = ChurchTrue THEN ChurchFalse ELSE ChurchTrue>> |
| 144 | + /\ depth' = depth + 1 |
| 145 | + |
| 146 | +EvalIfThenElse == |
| 147 | + /\ Len(evalStack) > 2 |
| 148 | + /\ LET condition == Head(evalStack) |
| 149 | + thenBranch == Head(Tail(evalStack)) |
| 150 | + elseBranch == Head(Tail(Tail(evalStack))) |
| 151 | + IN /\ evalStack' = Tail(Tail(Tail(evalStack))) \o <<IF condition = ChurchTrue THEN thenBranch ELSE elseBranch>> |
| 152 | + /\ depth' = depth + 1 |
| 153 | + |
| 154 | +EvalPair == |
| 155 | + /\ Len(evalStack) > 1 |
| 156 | + /\ LET first == Head(evalStack) |
| 157 | + second == Head(Tail(evalStack)) |
| 158 | + IN /\ evalStack' = Tail(Tail(evalStack)) \o <<[type |-> "Pair", left |-> first, right |-> second]>> |
| 159 | + /\ depth' = depth + 1 |
| 160 | + |
| 161 | +EvalFirst == |
| 162 | + /\ Len(evalStack) > 0 |
| 163 | + /\ LET pair == Head(evalStack) |
| 164 | + IN /\ evalStack' = Tail(evalStack) \o <<pair.left>> |
| 165 | + /\ depth' = depth + 1 |
| 166 | + |
| 167 | +EvalSecond == |
| 168 | + /\ Len(evalStack) > 0 |
| 169 | + /\ LET pair == Head(evalStack) |
| 170 | + IN /\ evalStack' = Tail(evalStack) \o <<pair.right>> |
| 171 | + /\ depth' = depth + 1 |
| 172 | + |
| 173 | +EvalYCombinator == |
| 174 | + (* Y combinator implementation *) |
| 175 | + UNCHANGED <<evalStack, depth>> |
| 176 | + |
| 177 | +Init == |
| 178 | + /\ evalStack = <<ChurchNumeral(3), ChurchNumeral(2)>> |
| 179 | + /\ depth = 0 |
| 180 | + /\ currentOp = "none" |
| 181 | + |
| 182 | +Next == |
| 183 | + /\ depth < MaxDepth |
| 184 | + /\ \/ /\ currentOp = "none" |
| 185 | + /\ \/ /\ currentOp' = "succ" |
| 186 | + /\ UNCHANGED <<evalStack, depth>> |
| 187 | + \/ /\ currentOp' = "pred" |
| 188 | + /\ UNCHANGED <<evalStack, depth>> |
| 189 | + \/ /\ currentOp' = "multiply" |
| 190 | + /\ UNCHANGED <<evalStack, depth>> |
| 191 | + \/ /\ UNCHANGED <<currentOp, evalStack, depth>> |
| 192 | + \/ /\ currentOp = "succ" |
| 193 | + /\ EvalSucc |
| 194 | + /\ currentOp' = "none" |
| 195 | + \/ /\ currentOp = "pred" |
| 196 | + /\ EvalPred |
| 197 | + /\ currentOp' = "none" |
| 198 | + \/ /\ currentOp = "multiply" |
| 199 | + /\ EvalMultiply |
| 200 | + /\ currentOp' = "none" |
| 201 | + \/ /\ depth >= MaxDepth |
| 202 | + /\ UNCHANGED <<evalStack, depth, currentOp>> |
| 203 | + |
| 204 | +Termination == depth >= MaxDepth |
| 205 | + |
| 206 | +Spec == Init /\ [][Next]_<<evalStack, depth, currentOp>> /\ WF_<<evalStack, depth, currentOp>>(Next) /\ SF_<<evalStack, depth, currentOp>>(Termination) |
| 207 | + |
| 208 | +TypeOK == |
| 209 | + /\ evalStack \in Seq([type: {"ChurchNumeral"}, |
| 210 | + value: Nat, |
| 211 | + left: [type: STRING, value: STRING], |
| 212 | + right: [type: STRING, value: STRING]]) |
| 213 | + /\ depth \in 0..MaxDepth |
| 214 | + /\ currentOp \in {"none", "succ", "pred", "multiply"} |
| 215 | + |
| 216 | +DepthInvariant == depth <= MaxDepth |
| 217 | + |
| 218 | +THEOREM Spec => [](TypeOK /\ DepthInvariant) |
| 219 | + |
| 220 | +==== |
0 commit comments