[Haskell-cafe] Specify array or list size?

Marcin 'Qrczak' Kowalczyk qrczak at knm.org.pl
Sat May 7 15:28:32 EDT 2005

Antti-Juhani Kaijanaho <antti-juhani at kaijanaho.info> writes:

>> No, it introduces a variable of type "array of 50 ints", which can be
>> converted to "pointer to int".
> ISO 9899:1999 (C99) section says that its type is "array of
> int", not "array of 50 ints":

Ok, so in C terminology "type" is different from most statically typed
languages in this respect. The dimension is used together with the
type to determine static properties, and says:

       [#4]  For  two array types to be compatible, both shall have
       compatible element types, and if both  size  specifiers  are
       present,  and  are  integer  constant expressions, then both
       size specifiers shall have the same constant value.  If  the
       two array types are used in a context which requires them to
       be compatible, it is undefined  behavior  if  the  two  size
       specifiers evaluate to unequal values.

In C++ the size is considered a part of the type:

  8.3.4  Arrays                                              [dcl.array]

1 In a declaration T D where D has the form
          D1 [constant-expressionopt]
  and  the  type  of the identifier in the declaration T D1 is "derived-
  declarator-type-list T," then the type of the identifier of  D  is  an
  array  type.   T is called the array element type; this type shall not
  be a reference type, the type void, a function  type  or  an  abstract
  class  type.  If the constant-expression (_expr.const_) is present, it
  shall be an integral  constant  expression  and  its  value  shall  be
  greater  than  zero.   The  constant expression specifies the bound of
  (number of elements in) the array.   If  the  value  of  the  constant
  expression  is  N, the array has N elements numbered 0 to N-1, and the
  type of the identifier of D is "derived-declarator-type-list array  of
  N  T."

In both languages lvalueness is also not considered a part of the type
but an alternative language presentation could use a wording where it is.

   __("<         Marcin Kowalczyk
   \__/       qrczak at knm.org.pl
    ^^     http://qrnik.knm.org.pl/~qrczak/

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