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The associativity and precedence of an operator is a part of the definition of the programming language; different programming languages may have different associativity and precedence for the same type of operator. Consider the expression a ~ b ~ c. If the operator ~ has left associativity, this expression would be interpreted as (a ~ b) ~ c.
The rank of an operation is called its precedence, and an operation with a higher precedence is performed before operations with lower precedence. Calculators generally perform operations with the same precedence from left to right, [ 1 ] but some programming languages and calculators adopt different conventions.
Operator associativity determines what happens when an operand is surrounded by operators of the same precedence, as in 1-2-3: An operator can be left-associative, right-associative, or non-associative. Left-associative operators are applied to operands in left-to-right order while right-associative operators are the other way round.
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).
Many operators differ syntactically from user-defined functions. In most languages, a function is prefix notation with fixed precedence level and associativity and often with compulsory parentheses (e.g. Func(a) or (Func a) in Lisp). In contrast, many operators are infix notation and involve different use of delimiters such as parentheses.
Unlike with functions, notational ambiguities can be overcome by means of additional definitions (e.g., rules of precedence, associativity of the operator). For example, in the programming language C , the operator - for subtraction is left-to-right-associative , which means that a-b-c is defined as (a-b)-c , and the operator = for assignment ...
The precedence of the conditional operator in Perl is the same as in C, not as in C++. This is conveniently of higher precedence than a comma operator but lower than the precedence of most operators used in expressions within the ternary operator, so the use of parentheses is rarely required.
Python sets are very much like mathematical sets, and support operations like set intersection and union. Python also features a frozenset class for immutable sets, see Collection types. Dictionaries (class dict) are mutable mappings tying keys and corresponding values. Python has special syntax to create dictionaries ({key: value})