How to change this function, “car” got problems
问题 I want to write a function, which converts from a "normal" notation like this: "1+4*2-8" to this pre-notation: "+1-*428". I hope you get the point here. Important: It must be in Strings. What I get so far: (define (converter lst ) (let ((operand1 (car lst)) (operator (car (cdr lst))) (operand2 (caddr lst))) (list operator (converter operand1) (converter operand2))) ) (infixLst->prefixLst '(1 + 2 * 3)) I got two problems here. 1) It's for Lists, I need it work for Strings like "1+3" and not '