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The shunting yard algorithm can also be applied to produce prefix notation (also known as Polish notation). To do this one would simply start from the end of a string of tokens to be parsed and work backwards, reverse the output queue (therefore making the output queue an output stack), and flip the left and right parenthesis behavior ...
In computer science, an operator-precedence parser is a bottom-up parser that interprets an operator-precedence grammar.For example, most calculators use operator-precedence parsers to convert from the human-readable infix notation relying on order of operations to a format that is optimized for evaluation such as Reverse Polish notation (RPN).
Infix notation is the notation commonly used in arithmetical and logical formulae and statements. It is characterized by the placement of operators between operands —"infixed operators"—such as the plus sign in 2 + 2 .
An operator which is non-associative cannot compete for operands with operators of equal precedence. In Prolog for example, the infix operator :-is non-associative, so constructs such as a :- b :- c are syntax errors. Unary prefix operators such as − (negation) or sin (trigonometric function) are typically associative prefix operators.
Order of operations arose due to the adaptation of infix notation in standard mathematical notation, which can be notationally ambiguous without such conventions, as opposed to postfix notation or prefix notation, which do not need orders of operations.
Compound terms with functors that are declared as operators can be written in prefix or infix notation. For example, the terms -(z), +(a,b) and =(X,Y) can also be written as -z, a+b and X=Y, respectively. Users can declare arbitrary functors as operators with different precedences to allow for domain-specific notations.
By convention, this prefix is only used in cases when the identifier would otherwise be either a reserved keyword (such as for and while), which may not be used as an identifier without the prefix, or a contextual keyword (such as from and where), in which cases the prefix is not strictly required (at least not at its declaration; for example ...
Expressions can be represented in prefix, postfix or infix notations and conversion from one form to another may be accomplished using a stack. Many compilers use a stack to parse syntax before translation into low-level code. Most programming languages are context-free languages, allowing them to be parsed with stack-based machines.