sci2exp

Arguments

a

a scilab object. The supported types are:

• booleans
• encoded integers of any inttype
• real or complex numbers
• sparse matrices
• polynomials
• strings, that may include some NewLine (ascii(10)) sequences
• a structures array or cells array with any number of dimensions
• a simple list whose components types are supported by sci2exp
• a typed list tlist() and mlist()
• a single graphic handle (only of figure or uicontrol).

For booleans, encoded integers, real or complex numbers, polynomials and strings, any of a single element or a vector or a matrix or an hypermatrix is accepted.

LHSname

Optional string: The name of the variable building the assignment prefix LHSname+" = ". When it is provided, LHSname+" = " is prepended to the raw expression yielded from the a object. Then, the result string t can no longer be evaluated with evstr() but with execstr().

t

Column of strings. A single whole string is returned when lmax is not used or is set to 0: The Scilab literal expression, with possibly the left-hand affectation part on the first line when LHSname is provided.

lmax

Positive integer setting the maximal length of the t components. The default value 0 ignores such a constrain and returns t as a single (long) string. Otherwise, some continuation marks .. are used to break too long rows.

Since continuation marks .. prevent using evstr() and execstr(), using this lmax option mostly cancels the main sci2exp() purpose.

Description

"sci2exp" stands for the conversion of a scilab object into a literal executable expression.

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.

Examples

With a numerical matrix:

a = [%i 2 ; 3 4-2*%i]
sci2exp(a)
sci2exp(a, 'aa')
sci2exp(a, 'aa', 10)

--> a = [%i 2 ; 3 4-2*%i]
 a  =
   i      2.
   3.     4. - 2.i

--> sci2exp(a)
 ans  =
 [%i,2;3,4-%i*2]

--> sci2exp(a, 'aa')
 ans  =
 aa = [%i,2;3,4-%i*2]

--> sci2exp(a, 'aa', 10)
 ans  =
!aa = [     !
!%i,2;      !
!3,4-%i*2]  !

With some other types of objects:

sci2exp(ssrand(2,2,2))                      // a typed list created with tlist()

sci2exp(figure("figure_name","figure1"))    // a graphic handle

Impact of format() on literal output numbers:

p = [0.123456789, %z-%pi*%i];
pol2str(p)                      // also impacted by format()
format(20);
Lp = sci2exp(p)                 // Literal encoding
Rp = evstr(Lp); pol2str(Rp)     // Regenerated from literal
Rp == p
format(10);                     // Let's truncate the literal output before calling sci2exp()
Lp = sci2exp(p)
Rp = evstr(Lp); format(20); pol2str(Rp)
Rp == p

--> p = [0.123456789, %z-%pi*%i];

--> pol2str(p)
 ans  =
!0.1234568  -%i*3.1415927+z  !

--> format(20)

--> Lp = sci2exp(p)
 Lp  =
 [0.12345678900000000,-%i*3.14159265358979310+%z]

--> Rp = evstr(Lp); pol2str(Rp)
 ans  =
!0.12345678900000000  -%i*3.14159265358979310+z  !

--> Rp == p
 ans  =
  T T


--> format(10)          // Let's truncate the literal output before calling sci2exp()

--> Lp = sci2exp(p)
 Lp  =
 [0.1234568,-%i*3.1415927+%z]

--> Rp = evstr(Lp); format(20); pol2str(Rp)
 ans  =
!0.12345680000000001  -%i*3.14159269999999990+z  !

--> Rp == p
 ans  =
  F F

See also

• string — преобразование в строку
• prettyprint — Converts a Scilab object into some corresponding LaTeX, TeX, MathML or HTML strings
• format — установка выходного формата десятичных чисел по умолчанию
• pol2str — polynomial to string conversion
• evstr — вычисление выражений
• execstr — execute Scilab code in strings

History