* Change in behavior of & operator between 83 and 9x? @ 1994-10-05 16:04 Paul Graham 0 siblings, 0 replies; 2+ messages in thread From: Paul Graham @ 1994-10-05 16:04 UTC (permalink / raw) If an array type A has component type B which is itself an array type, is it possible to concatenate two arrays of type B to produce an array of type A? For instance: package foo is type my_string is array(1 .. 3) of character; type my_string_vector is array(positive range <>) of my_string; c1 : my_string_vector := "abc" & "def"; end; In this example, I want the value of the concanenation to be equivalent to ("abc", "def") -- my_string_vector(1 to 2) But it can also be interpreted as "abcdef" -- string(1 to 6), my_string(1 to 6), ??? which does not match the type of c1. The 83 RM (4.5.3(4)) states "if both operands are one-dimensional arrays, the result of the concatenation is a one-dimensional array whose length is the sum of the lengths of the operands ...". Clearly the concatenation of two strings is always a string, and never an array of strings. But the 9x RM defines the result of a concatenation in terms of its result type. In the above example the result type is known to be my_string_vector. Thus the "&" should be "&"(x, y : my_string) return my_string_vector. Is my understanding wrong, or is this an incompatibility between the 83 and 9x versions of Ada? Paul -- Paul Graham graham@compass-da.com Compass Design Automation, Inc. (speaking only for myself) "Cekoslovakyalilastiramadiklarimizdanmissiniz." ^ permalink raw reply [flat|nested] 2+ messages in thread
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* Re: Change in behavior of & operator between 83 and 9x? [not found] <19941006.090935.490@vnet.ibm.com> @ 1994-10-13 1:43 ` Keith Thompson @pulsar 0 siblings, 0 replies; 2+ messages in thread From: Keith Thompson @pulsar @ 1994-10-13 1:43 UTC (permalink / raw) In <19941006.090935.490@vnet.ibm.com> karthurs@vnet.ibm.com (Keith Arthurs) writes: > In article <GRAHAM.94Oct5120449@canopus.clsi.COM>, > on 05 Oct 1994 16:04:49 GMT, > Paul Graham <graham@clsi.COM> writes: > > > >If an array type A has component type B which is itself an array type, is it > >possible to concatenate two arrays of type B to produce an array of type A? > >For instance: > > > > package foo is > > type my_string is array(1 .. 3) of character; > > type my_string_vector is array(positive range <>) of my_string; > > c1 : my_string_vector := "abc" & "def"; > > In Ada 83 'my_string_vector' would need to be constrained (1 .. 2) > (lrm 3.6.1:6) > > > end; > > > >In this example, I want the value of the concanenation to be equivalent to > > > > ("abc", "def") -- my_string_vector(1 to 2) > > This is a correct interpretation of 'my_string_vector', it is a two > dimensional array A quibble: it's not a two dimensional array, it's a one dimensional array whose component type is also a one dimensional array. (Unlike Pascal, for example, Ada does distinguish between these two cases.) For example: type Array_1d is array(1 .. 3) of Integer; type Array_1d_1d is array(1 .. 3) of Array_1d; -- -- Array_1d_1d is a 1-d array of 1-d arrays -- type Array_2d is array(1 .. 3, 1 .. 3) of Integer; -- -- Array_2d is a 2-d array -- Just to add to the confusion, both types use the same syntax for aggregates: Obj_1d_1d: Array_1d_1d := (1 => (1, 2, 3), 2 => (4, 5, 6), 3 => (7, 8, 9)); Obj_2d: Array_2d := (1 => (1, 2, 3), 2 => (4, 5, 6), 3 => (7, 8, 9)); -- Keith Thompson (The_Other_Keith) kst@alsys.com TeleSoft^H^H^H^H^H^H^H^H Alsys, Inc. 10251 Vista Sorrento Parkway, Suite 300, San Diego, CA, USA, 92121-2718 /user/kst/.signature: I/O error (core dumped) ^ permalink raw reply [flat|nested] 2+ messages in thread
end of thread, other threads:[~1994-10-13 1:43 UTC | newest] Thread overview: 2+ messages (download: mbox.gz / follow: Atom feed) -- links below jump to the message on this page -- 1994-10-05 16:04 Change in behavior of & operator between 83 and 9x? Paul Graham [not found] <19941006.090935.490@vnet.ibm.com> 1994-10-13 1:43 ` Keith Thompson @pulsar
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