Convert A String to List in Prolog -


i prolog newbie , stuck @ parsing string list. have string of form. want read polynomial string , convert string. want convert input string

2x^3 + x^2 - 4x^1 - 8

to

[[2,3], [1,2], [-4, 1], [-8, 0]]

how can achieve functionality?

this problem solved in 2 steps:

  1. lexical analysis / tokenizer: convert string list of tokens represent each of possible elements of expression: numbers, variable names , operators. representations maybe, instance, terms number(v), vname(n) , op(op); may wish use different terms additive operators separate monomials , exponent operator.
  2. syntactic analysis / parser: apply grammar rules list of tokens identify monomials , convert them required representation. in case each rule have form of clause inspects appears @ beginning of tokens list find monomial , convert it.
sample rules be

monom([number(n),vname(x),op(exp),number(e)|ts],[[n,e]|ms]) :-   !, monom(ts,ms).  monom([number(n),vname(x),op(+)|ts],[[n,1]|ms]) :-   !, monom([op(+)|ts],ms).

note these rules not check whether variables have same name. issue using minus sign of monomial. hope able cope this.


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