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Scilab Help >> Advanced functions > overloading


display, functions and operators overloading capabilities


In Scilab, variable display, functions and operators may be defined for new objects using functions (Scilab coded or primitives).


The display of new objects defined by tlist structure may be overloaded (the default display is similar to list's one). The overloading function must have no output argument and a single input argument. It's name is formed as follow %<tlist_type>_p where %<tlist_type> stands for the first entry of the tlist type component truncated to the first 9 characters.


Each operator which is not defined for given operands type may be defined. The overloading function must have a single output argument and one or two inputs according to the number of operands. The function name is formed as follow:

for binary operators: %<first_operand_type>_<op_code>_<second_operand_type>;

for unary operators: %<operand_type>_<op_code>;

extraction and insertion operators which are n-nary operators are described below.

Be careful, only the types registered by the typename function can be used in an overloading macros.

<operand_type>, <first_operand_type>, <second_operand_type> are sequence of characters associated with each data type as described in the following table:

data type char code typeof comments
double matrix s constant
polynomial matrix p polynomial
boolean matrix b boolean
sparse matrix sp sparse
boolean sparse matrix spb boolean sparse
Matlab sparse matrix msp Matlab sparse
integer matrix i int8, int16, int32, uint8, uint16, uint32
string matrix c string
handle h handle
compiled function fptr fptr
script function mc function
library f library
list l list
tlist tlist type tlist type the first string in the first tlist entry
mlist mlist type mlist type the first string in the first mlist entry
hypermatrix hm hypermat
pointer ptr pointer
cell ce ce
structure st st
rational r rational
linear state space lss state-space
implicit polynom ip size implicit 1:1:$

<op_code> is a single character associated with each operator as described in the following table:

op char code
' t
+ a
- s
* m
/ r
\ l
^ p
.* x
./ d
.\ q
.*. k
./. y
.\. z
: b
*. u
/. v
\. w
[a,b] c
[a;b] f
() extraction e
() insertion i
== o
<> n
| g
& h
.^ j
.' 0
< 1
> 2
<= 3
>= 4
~ 5
iext 6

The overloading function for extraction syntax b= a(i1, ..., in) has the following calling sequence: b = %<type_of_a>_e_(i1, ..., in, a)

and the syntax [x1, .., xm] = a(i1, ..., in) has the following calling sequence: [x1, .., xm] = %<type_of_a>_e_(i1, ..., in, a) .

The overloading function associated to the insertion syntax a(i1, ..., in) = b has the following calling sequence: a = %<type_of_b>_i_<type_of_a>(i1, ..., in, b, a) .

The 6 char code may be used for some complex insertion algorithm like x.b(2) = 33 where b field is not defined in the structure x. The insertion is automatically decomposed into temp = x.b; temp(2) = 33; x.b = temp. The 6 char code is used for the first step of this algorithm. The 6 overloading function is very similar to the e's one.

Functions :

Some basic primitive function may also be overloaded for new data type. When such function is undefined for a particular data types the function %<type_of_an_argument>_<function_name> is called. User may add in this called function the definition associated with the input data types.


            var = tlist('tab', ['a', 'b'], ['x'; 'y'], rand(2, 2)) // the type of var is 'tab'
            function []=%tab_p(l)
            disp([[' '; l(3)] [l(2); string(l(4))]])
            var // after overloading
            's' + 1 // it is impossible to add a number to a string
            function x=%c_a_s(a, b)
            x = a + string(b);
            's' + 1 // after overloading
            sin('2 * x') // the sin function does not work with a string
            function x=%c_sin(a)
            x = 'sin(' + a + ')'
            sin('2 * x') // after overloading

See Also

  • tlist — Scilab object and typed list definition.
  • disp — displays variables
  • symbols — scilab operator names
  • typeof — object type
  • type — returns the type of a variable
  • typename — associates a name to variable type
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Last updated:
Thu Oct 02 13:47:02 CEST 2014