sci2exp

Literal values of decimal real or complex numbers or coefficients are output in t according to the current format setting. So, they may be truncated with respect to the full numerical accuracy.

When a are polynomials, the resulting expression t can be executed to regenerate a ONLY if the formal variable of the polynomials is defined in the current scope:

• For polynomials in s or z, the predefined Scilab variables %s or %z are used, and the regeneration can be straightforward:

                                  --> p = [1+%z 1-%z^2];
                                  
                                  --> tp = pol2str(p)
                                   tp  =
                                  !1+z  1-z^2  !
                                  
                                  --> evstr(tp)
                                  at line     1 of executed string
                                  at line    38 of function        evstr ( SCI\modules\string\macros\evstr.sci line 52 )
                                  Undefined variable: z
                                  
                                  --> tp = sci2exp(p)
                                   tp  =
                                   [1+%z,1-%z^2]        <<< sci2exp() uses the variable %z as predefined "z" generator
                                  
                                  --> t = evstr(tp)     // .. straigntforward regeneration
                                   t  =
                                                2
                                     1 +z   1 -z
                                  
                                  --> typeof(t)
                                   ans  =
                                   polynomial
                                  

• Otherwise: The formal variable of a -- say "x" -- must be explicitly defined with (say) x = poly(0,"x"):

                                  --> p = poly([1 2 3], "x")
                                   p  =
                                               2   3
                                    -6 +11x -6x  +x
                                  
                                  --> tp = sci2exp(p)
                                   tp  =
                                   -6+11*x-6*x^2+x^3
                                  
                                  --> // Evaluating tp now would yield an error: x is not yet defined. We must prioly do:
                                  
                                  --> x = poly(0,"x")  // Defines the symbolic variable "x" in the actual variable with the SAME name
                                   x  =
                                     x
                                  
                                  --> // Then evaluating tp to regenerate p is OK:
                                  --> rp = evstr(tp)
                                   rp  =
                                               2   3
                                    -6 +11x -6x  +x
                                  
                                  --> rp==p
                                   ans  =
                                    T
                                  

When a is a graphic handle, sci2exp ignores its parent (empty) and its children.