Erlang Dialyzer整数范围

问题描述

-module(test).
-export([f/0, g/0]).

-spec f() -> RESULT when
      RESULT :: 0..12 .

-spec g() -> RESULT when
      RESULT :: 0..13 .

f () -> 100 .

g () -> 100 .

仅运行功能f的透析器(和键入器)正在运行.

Running dialyzer (and typer) only the function f is caught.

dialyzer test.erl
Checking whether the PLT /Users/ben/.dialyzer_plt is up-to-date... yes
Proceeding with analysis...
test.erl:4: Invalid type specification for function test:f/0. The success typing is () -> 100
 done in 0m0.53s
done (warnings were emitted)

与打字机相同

typer test.erl
typer: Error in contract of function test:f/0
         The contract is: () -> RESULT when RESULT :: 0..12
         but the inferred signature is: () -> 100

这是预期"行为吗?

推荐答案

是的，它似乎确实是预期的".查看源代码此处它针对

Yes it does seem to be "expected".Looking at the source code hereIt tests against the value of

-define(SET_LIMIT, 13).

在测试中

t_from_range(X, Y) when is_integer(X), is_integer(Y) ->
  case ((Y - X) < ?SET_LIMIT) of 
    true -> t_integers(lists:seq(X, Y));
    false ->
      case X >= 0 of
    false -> 
      if Y < 0 -> ?integer_neg;
         true -> t_integer()
      end;
    true ->
      if Y =< ?MAX_BYTE, X >= 1 -> ?int_range(1, ?MAX_BYTE);
         Y =< ?MAX_BYTE -> t_byte();
         Y =< ?MAX_CHAR, X >= 1 -> ?int_range(1, ?MAX_CHAR);
         Y =< ?MAX_CHAR -> t_char();
         X >= 1         -> ?integer_pos;
         X >= 0         -> ?integer_non_neg
      end
      end
  end;

恕我直言，这似乎很危险，并且没有提供任何真正的保证.绝对应该清楚地记录下来.在学习一些Erlang网站上.

IMHO this seems dangerous, and does not provide any real guarantees. It should definitely be documented clearly. there is passing reference on the learn you some Erlang website.

但是使用关键字dialyzer integer ranges

编辑...再仔细一点，您会发现，如果尝试:

Edit... looking a bit closer you can see that if you try:

-module(test).
-export([h/0]).

-spec h() -> RESULT when
      RESULT :: 1..13 .

h () -> 100 .

Dialyzer将捕获该错误！ (Typer不会)...

Dialyzer will catch the error! (Typer will not) ...

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