diff --git a/README.md b/README.md index be5379d..8fbb8c4 100644 --- a/README.md +++ b/README.md @@ -164,6 +164,11 @@ Supported unary operators: | - | 110 | Negation | | ! | 110 | Logical not | +Operators that take numbers as arguments can either take integers or floating point numbers. +If one of the arguments is a floating point number, all others are converted to floating point numbers as well, and the resulting value is a floating point number as well. +Otherwise, the result is an integer. +An exception to this is the exponentiation operator that always returns a floating point number. + #### The Aggregation Operator The aggregation operator aggregates a set of values into a tuple. @@ -321,8 +326,8 @@ This crate offers a set of builtin functions. | `min` | >= 1 | Numeric | Returns the minimum of the arguments | | `max` | >= 1 | Numeric | Returns the maximum of the arguments | | `len` | 1 | String/Tuple | Returns the character length of a string, or the amount of elements in a tuple (not recursively) | -| `str::regex_matches` | 2 | String, String | Returns true if the first argument matches the regex in the second argument | -| `str::regex_replace` | 3 | String, String, String | Returns the first argument with all matches of the regex in the second argument replaced by the third argument | +| `str::regex_matches` | 2 | String, String | Returns true if the first argument matches the regex in the second argument (Requires `regex_support` feature flag) | +| `str::regex_replace` | 3 | String, String, String | Returns the first argument with all matches of the regex in the second argument replaced by the third argument (Requires `regex_support` feature flag) | | `str::to_lowercase` | 1 | String | Returns the lower-case version of the string | | `str::to_uppercase` | 1 | String | Returns the upper-case version of the string | | `str::trim` | 1 | String | Strips whitespace from the start and the end of the string | @@ -375,53 +380,22 @@ The type of a value can be checked using the `Value::is_[type]` methods. | `Value::from(4.4).as_float()` | `Ok(4.4)` | | `Value::from(true).as_int()` | `Err(Error::ExpectedInt {actual: Value::Boolean(true)})` | -Operators that take numbers as arguments can either take integers or floating point numbers. -If one of the arguments is a floating point number, all others are converted to floating point numbers as well, and the resulting value is a floating point number as well. -Otherwise, the result is an integer. -An exception to this is the exponentiation operator that always returns a floating point number. - Values have a precedence of 200. ### Variables This crate allows to compile parameterizable formulas by using variables. A variable is a literal in the formula, that does not contain whitespace or can be parsed as value. -The user needs to provide bindings to the variables for evaluation. -This is done with the `Context` trait. -Two structs implementing this trait are predefined. -There is `EmptyContext`, that returns `None` for each request, and `HashMapContext`, that stores mappings from literals to variables in a hash map. +For working with variables, a [context](#contexts) is required. +It stores the mappings from variables to their values. Variables do not have fixed types in the expression itself, but are typed by the context. -The `Context` trait contains a function that takes a string literal and returns a `Value` enum. -The variant of this enum decides the type on evaluation. +Once a variable is assigned a value of a specific type, it cannot be assigned a value of another type. +This might change in the future and can be changed by using a type-unsafe context (not provided by this crate as of now). -Variables have a precedence of 200. +Here are some examples and counter-examples on expressions that are interpreted as variables: -### User-Defined Functions - -This crate also allows to define arbitrary functions to be used in parsed expressions. -A function is defined as a `Function` instance. -It contains two properties, the `argument_amount` and the `function`. -The `function` is a boxed `Fn(&[Value]) -> EvalexprResult`. -The `argument_amount` determines the length of the slice that is passed to `function` if it is `Some(_)`, otherwise the function is defined to take an arbitrary amount of arguments. -It is verified on execution by the crate and does not need to be verified by the `function`. - -Functions with no arguments are not allowed. -Use variables instead. - -Be aware that functions need to verify the types of values that are passed to them. -The `error` module contains some shortcuts for verification, and error types for passing a wrong value type. -Also, most numeric functions need to differentiate between being called with integers or floating point numbers, and act accordingly. - -Functions are identified by literals, like variables as well. -A literal identifies a function, if it is followed by an opening brace `(`, another literal, or a value. - -Same as variables, function bindings are provided by the user via a `Context`. -Functions have a precedence of 190. - -### Examplary variables and functions in expressions: - -| Expression | Valid? | Explanation | +| Expression | Variable? | Explanation | |------------|--------|-------------| | `a` | yes | | | `abc` | yes | | @@ -431,6 +405,38 @@ Functions have a precedence of 190. | `true` | no | Expression is interpreted as `Value::Bool` | | `.34` | no | Expression is interpreted as `Value::Float` | +Variables have a precedence of 200. + +### User-Defined Functions + +This crate also allows to define arbitrary functions to be used in parsed expressions. +A function is defined as a `Function` instance, wrapping a boxed `Fn(&[Value]) -> EvalexprResult`. +The definition needs to be included in the [`Context`](#contexts) that is used for evaluation. +As of now, functions cannot be defined within the expression, but that might change in the future. + +The function gets passed what ever value is directly behind it, be it a tuple or a single values. +If there is no value behind a function, it is interpreted as a variable instead. +More specifically, a function needs to be followed by either an opening brace `(`, another literal, or a value. +While not including special support for multi-valued functions, they can be realized by requiring a single tuple argument. + +Be aware that functions need to verify the types of values that are passed to them. +The `error` module contains some shortcuts for verification, and error types for passing a wrong value type. +Also, most numeric functions need to differentiate between being called with integers or floating point numbers, and act accordingly. + +Here are some examples and counter-examples on expressions that are interpreted as function calls: + +| Expression | Variable? | Explanation | +|------------|--------|-------------| +| `a v` | yes | | +| `x 5.5` | yes | | +| `a (3, true)` | yes | | +| `a b 4` | yes | Call `a` with the result of calling `b` with `4` | +| `5 b` | no | Error, value cannot be followed by a literal | +| `12 3` | no | Error, value cannot be followed by a value | +| `a 5 6` | no | Error, function call cannot be followed by a value | + +Functions have a precedence of 190. + ### [Serde](https://serde.rs) To use this crate with serde, the `serde_support` feature flag has to be set. diff --git a/src/lib.rs b/src/lib.rs index b3184d6..f9e915b 100644 --- a/src/lib.rs +++ b/src/lib.rs @@ -151,6 +151,11 @@ //! | - | 110 | Negation | //! | ! | 110 | Logical not | //! +//! Operators that take numbers as arguments can either take integers or floating point numbers. +//! If one of the arguments is a floating point number, all others are converted to floating point numbers as well, and the resulting value is a floating point number as well. +//! Otherwise, the result is an integer. +//! An exception to this is the exponentiation operator that always returns a floating point number. +//! //! #### The Aggregation Operator //! //! The aggregation operator aggregates a set of values into a tuple. @@ -308,8 +313,8 @@ //! | `min` | >= 1 | Numeric | Returns the minimum of the arguments | //! | `max` | >= 1 | Numeric | Returns the maximum of the arguments | //! | `len` | 1 | String/Tuple | Returns the character length of a string, or the amount of elements in a tuple (not recursively) | -//! | `str::regex_matches` | 2 | String, String | Returns true if the first argument matches the regex in the second argument | -//! | `str::regex_replace` | 3 | String, String, String | Returns the first argument with all matches of the regex in the second argument replaced by the third argument | +//! | `str::regex_matches` | 2 | String, String | Returns true if the first argument matches the regex in the second argument (Requires `regex_support` feature flag) | +//! | `str::regex_replace` | 3 | String, String, String | Returns the first argument with all matches of the regex in the second argument replaced by the third argument (Requires `regex_support` feature flag) | //! | `str::to_lowercase` | 1 | String | Returns the lower-case version of the string | //! | `str::to_uppercase` | 1 | String | Returns the upper-case version of the string | //! | `str::trim` | 1 | String | Strips whitespace from the start and the end of the string | @@ -362,53 +367,22 @@ //! | `Value::from(4.4).as_float()` | `Ok(4.4)` | //! | `Value::from(true).as_int()` | `Err(Error::ExpectedInt {actual: Value::Boolean(true)})` | //! -//! Operators that take numbers as arguments can either take integers or floating point numbers. -//! If one of the arguments is a floating point number, all others are converted to floating point numbers as well, and the resulting value is a floating point number as well. -//! Otherwise, the result is an integer. -//! An exception to this is the exponentiation operator that always returns a floating point number. -//! //! Values have a precedence of 200. //! //! ### Variables //! //! This crate allows to compile parameterizable formulas by using variables. //! A variable is a literal in the formula, that does not contain whitespace or can be parsed as value. -//! The user needs to provide bindings to the variables for evaluation. -//! This is done with the `Context` trait. -//! Two structs implementing this trait are predefined. -//! There is `EmptyContext`, that returns `None` for each request, and `HashMapContext`, that stores mappings from literals to variables in a hash map. +//! For working with variables, a [context](#contexts) is required. +//! It stores the mappings from variables to their values. //! //! Variables do not have fixed types in the expression itself, but are typed by the context. -//! The `Context` trait contains a function that takes a string literal and returns a `Value` enum. -//! The variant of this enum decides the type on evaluation. +//! Once a variable is assigned a value of a specific type, it cannot be assigned a value of another type. +//! This might change in the future and can be changed by using a type-unsafe context (not provided by this crate as of now). //! -//! Variables have a precedence of 200. +//! Here are some examples and counter-examples on expressions that are interpreted as variables: //! -//! ### User-Defined Functions -//! -//! This crate also allows to define arbitrary functions to be used in parsed expressions. -//! A function is defined as a `Function` instance. -//! It contains two properties, the `argument_amount` and the `function`. -//! The `function` is a boxed `Fn(&[Value]) -> EvalexprResult`. -//! The `argument_amount` determines the length of the slice that is passed to `function` if it is `Some(_)`, otherwise the function is defined to take an arbitrary amount of arguments. -//! It is verified on execution by the crate and does not need to be verified by the `function`. -//! -//! Functions with no arguments are not allowed. -//! Use variables instead. -//! -//! Be aware that functions need to verify the types of values that are passed to them. -//! The `error` module contains some shortcuts for verification, and error types for passing a wrong value type. -//! Also, most numeric functions need to differentiate between being called with integers or floating point numbers, and act accordingly. -//! -//! Functions are identified by literals, like variables as well. -//! A literal identifies a function, if it is followed by an opening brace `(`, another literal, or a value. -//! -//! Same as variables, function bindings are provided by the user via a `Context`. -//! Functions have a precedence of 190. -//! -//! ### Examplary variables and functions in expressions: -//! -//! | Expression | Valid? | Explanation | +//! | Expression | Variable? | Explanation | //! |------------|--------|-------------| //! | `a` | yes | | //! | `abc` | yes | | @@ -418,6 +392,38 @@ //! | `true` | no | Expression is interpreted as `Value::Bool` | //! | `.34` | no | Expression is interpreted as `Value::Float` | //! +//! Variables have a precedence of 200. +//! +//! ### User-Defined Functions +//! +//! This crate also allows to define arbitrary functions to be used in parsed expressions. +//! A function is defined as a `Function` instance, wrapping a boxed `Fn(&[Value]) -> EvalexprResult`. +//! The definition needs to be included in the [`Context`](#contexts) that is used for evaluation. +//! As of now, functions cannot be defined within the expression, but that might change in the future. +//! +//! The function gets passed what ever value is directly behind it, be it a tuple or a single values. +//! If there is no value behind a function, it is interpreted as a variable instead. +//! More specifically, a function needs to be followed by either an opening brace `(`, another literal, or a value. +//! While not including special support for multi-valued functions, they can be realized by requiring a single tuple argument. +//! +//! Be aware that functions need to verify the types of values that are passed to them. +//! The `error` module contains some shortcuts for verification, and error types for passing a wrong value type. +//! Also, most numeric functions need to differentiate between being called with integers or floating point numbers, and act accordingly. +//! +//! Here are some examples and counter-examples on expressions that are interpreted as function calls: +//! +//! | Expression | Variable? | Explanation | +//! |------------|--------|-------------| +//! | `a v` | yes | | +//! | `x 5.5` | yes | | +//! | `a (3, true)` | yes | | +//! | `a b 4` | yes | Call `a` with the result of calling `b` with `4` | +//! | `5 b` | no | Error, value cannot be followed by a literal | +//! | `12 3` | no | Error, value cannot be followed by a value | +//! | `a 5 6` | no | Error, function call cannot be followed by a value | +//! +//! Functions have a precedence of 190. +//! //! ### [Serde](https://serde.rs) //! //! To use this crate with serde, the `serde_support` feature flag has to be set.