sci_files

How to write conversion functions

Description

To convert calls to Matlab functions, mfile2sci uses a function called sci_<Matlab_function_name>. All these functions are defined in sci_files in directory SCI/modules/m2sci/macros/sci_files/. The set of sci_files given in Scilab distribution does not allow to convert calls to all Matlab functions yet. However, a Scilab user can add sci_files (for Matlab functions or for user defined functions) to Scilab using the following tips.

In M2SCI, a function call is considered as a “tree” (it is also the case for the instructions of the file to convert), represented in Scilab by a tlist with following fields:

• :name Matlab function name : :lhsnb number of Matlab function output parameters : :lhs list of Matlab function output parameters : :rhs list of Matlab function input parameters :

A sci_function has one input called tree which is also the output of the function. A sci_function has to convert this incoming “tree” so that it is compatible with Scilab by changing name, lhsnb, lhs and/or rhs. The other task that has to be done by this function is inference. Incoming tree contains inference data in its lhs that have to be updated with what can be infered for the outputs of this function.

Some useful functions have been written to help to create M2SCI tlists while writing this conversion function:

• :Funcall create a tree representing a function call : :Operation create a tree representing an operation : :Variable create a tree representing a variable : :Cste create a tree representing a constante value : :Infer create a tree representing inference data : :Type create a tree representing type for inference : :Equal create a tree representing an instruction :

Some other functions have been designed to get properties of operands/inputs. Considering A is tlist used in macro tree, you can use the following functions: Function returns %T if... is_empty(A) all dimensions of A are 0 not_empty(A) all dimensions of A are known and at least one dimension of A is not 0 is_a_scalar(A) all dimensions of A are 1 not_a_scalar(A) all dimensions of A are known and at least one dimension of A is not 1 is_a_vector(A) all dimensions of A are known and all dimensions of A but one are equal to 1 not_a_vector(A) all dimensions of A are known and at least two dimensions of A are greater than one is_real(A) A is real is_complex(A) A is complex isdefinedvar(A) A is a variable already created in M-file currently converted allunknown(A) all dimensions of A are unknown Some other functions have been written for specific needs while writing conversion files:

• :first_non_singleton is an equivalent to firstnonsingleton for an

  M2SCI tlist. Calling sequence: dim = first_non_singleton(A)

  : :gettempvar generates a temporary variable having a name which does

  not already exist. Calling sequence: v = gettempvar()

  : :insert allows to insert instructions. Calling sequence:

  insert(Equal(...),opt) with opt~=1 to insert before current instruction and opt=1 to insert after it.

  : :getoperands can be used to get each operand as a variable. Calling

  sequence: [A,B] = getoperands(operation_tlist)

  : :getrhs can be used to get each parameter as a variable. Calling

  sequence: [A,...] = getrhs(funcall_tlist)

  : :convert2double change type of input when this type is not

  implemented for a particular function is Scilab. Calling sequence: A = convert2double(A)

  :

To have more information about how to write such files, refer to directory SCI/modules/m2sci/macros/sci_files/ which gives many examples from very simple ones (e.g. sci_abs.sci) to very complex ones (e.g. sci_zeros.sci).

See Also

• m2scideclare Giving tips to help M2SCI...
• Funcall Create a tree representing a function call
• Operation Create a tree representing an operation
• Variable Create a tree representing a variable
• Cste Create a tree representing a constant
• Infer Create a tree containing inference data
• Type Create a tree containing type inference data
• Equal Create a tree representing an instruction