问题描述
我刚刚写完这篇模式匹配(下面附上)。无论我如何尝试修复它,当我尝试编译它时仍然出现“错误:语法错误”。
let rec stmt (s:Ast.stmt) : X86.inst list =
let get_label e =
let inst = stmt e in
let pattern = (List.nth (List.rev inst) 0) in
let label = match pattern with
|Memory (Store (Addr (Label l),Reg r)) -> l
|_ -> "Error"
in
match s with
|Exp e -> (match e with
|Int i -> [movei RAX i; store new_temp() RAX]
|Var v -> [load RBX v; store new_temp() RBX]
|Binop (e1,op,e2) -> let (label1,label2) = (get_label e1,get_label e2)
in let operation =
match op with
|Plus -> [Arith (Add (RAX,Reg RBX))]
|Minus -> [Arith (Sub (RAX,Reg RBX))]
|Times -> [Arith (Mul RBX)]
|Div -> [Arith (Div RBX)]
|Eq -> [Arith (Cmp (RAX,RBX))]
|Neq -> [Arith (Cmp (RAX,Reg RBX)); set NE RAX]
|Lt -> [Arith (Cmp (RAX,Reg RBX)); set L RAX]
|Lte -> [Arith (Cmp (RAX,Reg RBX)); set LE RAX]
|Gt -> [Arith (Cmp (RAX,Reg RBX)); set G RAX]
|Gte -> [Arith (Cmp (RAX,Reg RBX)); set GE RAX]
in [load RAX label1; load RBX label2] @ operation @ [store (new_temp()) RAX]
|Not e -> let label = get_label e in
[load RBX label; Arith (Neg RBX); store (new_temp()) RAX]
|And (e1,get_label e2) in
[load RAX label1; load RBX label2; Bitop (And (RAX,Reg RBX)); store (new_temp()) RAX]
|Or (e1,get_label e2) in
[load RAX label1; load RBX label2; Bitop (Or (RAX,Reg RBX)); store (new_temp()) RAX]
|Assign (e1,e2) -> let label = get_label e2 in
[movei RAX label; store e1 RAX; store (new_temp()) RAX]
|_ -> [])
|Block e -> []
|If (l,m,r) -> []
|While (l,r) -> []
|For (l,m1,m2,r) -> []
|Return e -> []
|_ -> []
let compile (p : Ast.program) : result =
let _ = reset() in
let _ = collect_vars(p) in
let insts = List.concat_map stmt p in
{ code = insts; data = VarSet.elements !variables }
错误位于 let compile (p: Ast.program) : result =
这是(来自外壳):
110 | let compile (p : Ast.program) : result =
^^^
Error: Syntax error
解决方法
由于没有正确完成 get_label
函数而导致的错误:
let get_label e =
let inst = stmt e in
let pattern = (List.nth (List.rev inst) 0) in
let label = match pattern with
|Memory (Store (Addr (Label l),Reg r)) -> l
|_ -> "Error"
因此,尽管有缩进,它后面的 in
与 let label = ...
相关联,而不是 let get_label e = ...
。
我怀疑您想要的是跳过 label
绑定:
let get_label e =
let inst = stmt e in
let pattern = (List.nth (List.rev inst) 0) in
match pattern with
| Memory (Store (Addr (Label l),Reg r)) -> l
| _ -> "Error"
使用像 ocp-indent
这样的工具可能是个好主意,它会根据编译器如何解释代码来缩进你的代码,而不是你希望编译器如何解释它。这通常有助于避免这样的错误:)