.
-- concatenate objectsobject1.object2
concatenates two objects.
_concat(object1, object2, ...)
concatenates an
arbitrary number of objects.
object1 . object2
_concat(object1, object2...)
object1 |
- | a character string, an identifier, or a list |
object2 |
- | a character string, an identifier, an integer, or a list |
an object of the same type as object1
.
object1
, object2
, ...
_concat(object1, object2)
is equivalent to
object1.object2
. The function call _concat(object1,
object2, object3, ...)
is equivalent to
((object1.object2).object3). ...
._concat()
returns the void object of type
DOM_NULL
.object1 |
object2 |
object1.object2 |
string | string | string |
string | identifier | string |
string | integer | string |
identifier | string | identifier |
identifier | identifier | identifier |
identifier | integer | identifier |
list | list | list |
x.1
creates the identifier x1
.x := y
, i := 1
, the
concatenation x.i
produces the identifier y1
.
However, the resulting identifier y1
is not fully
evaluated. Cf. example 2._concat
is a function of the system kernel.We demonstrate all possible combinations of types that can be concatenated. Strings are produced if the first object is a string:
>> "x"."1", "x".y, "x".1
"x1", "xy", "x1"
Identifiers are produced if the first object is an identifier:
>> x."1", x.y , x.1
x1, xy, x1
The concatenation operator .
also serves
for concatenating lists:
>> [1, 2] . [3, 4]
[1, 2, 3, 4]
>> L := []: for i from 1 to 10 do L := L . [x.i] end_for: L
[x1, x2, x3, x4, x5, x6, x7, x8, x9, x10]
>> delete L:
We demonstrate the evaluation strategy of concatenation. Before concatenation, the objects are evaluated:
>> x := "Val": i := ue: x.i
"Value"
>> ue := 1: x.i
"Val1"
An identifier produced via concatenation is not fully evaluated:
>> delete x: x1 := 17: x.1, eval(x.1)
x1, 17
The .
operator can be used to create
variables dynamically. They can be assigned values immediately:
>> delete x: for i from 1 to 5 do x.i := i^2 end_for:
Again, the result of the concatenation is not fully evaluated:
>> x.i $ i= 1..5
x1, x2, x3, x4, x5
>> eval(%)
1, 4, 9, 16, 25
>> delete i, ue: (delete x.i) $ i = 1..5:
The function _concat
can be used to
concatenate an arbitrary number of objects:
>> _concat("an", " ", "ex", "am", "ple")
"an example"
>> _concat("0", " ".i $ i = 1..15)
"0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15"
>> _concat([], [x.i] $ i = 1..10)
[x1, x2, x3, x4, x5, x6, x7, x8, x9, x10]