# formulae v0.8.0 Formulae View Source

A set of functions to deal with analytical formulae.

The typical way of using this module would be to call `Formulae.compile/1` on the binary representing the string.

``````iex|1 ▶ f = Formulae.compile "a + :math.sin(3.14 * div(b, 2)) - c"

%Formulae{
ast: {:-, [line: 1],
[
{:+, [line: 1],
[
{:a, [line: 1], nil},
{{:., [line: 1], [:math, :sin]}, [line: 1],
[{:*, [line: 1], [3.14, {:div, [line: 1], [{:b, [line: 1], nil}, 2]}]}]}
]},
{:c, [line: 1], nil}
]},
eval: &:"Elixir.Formulae.a + :math.sin(3.14 * div(b, 2)) - c".eval/1,
formula: "a + :math.sin(3.14 * div(b, 2)) - c",
module: :"Elixir.Formulae.a + :math.sin(3.14 * div(b, 2)) - c",
variables: [:a, :b, :c]
}``````

Now the formula is compiled and might be invoked by calling `Formulae.eval/2` passing a formula and bindings. First call to `eval/2` would lazily compile the module if needed.

``````iex|2 ▶ f.eval.(a: 3, b: 4, c: 2)
0.9968146982068622``````

The formulae might be curried.

``````iex|3 ▶ Formulae.curry(f, a: 3, b: 4)
%Formulae{
ast: ...,
eval: &:"Elixir.Formulae.3 + :math.sin(3.14 * div(4, 2)) - c".eval/1,
formula: "3 + :math.sin(3.14 * div(4, 2)) - c",
module: :"Elixir.Formulae.3 + :math.sin(3.14 * div(4, 2)) - c",
variables: [:c]
}``````

# Link to this section Summary

## Types

The formulae is internally represented as struct, exposing the original binary representing the formula, AST, the module this formula was compiled into, variables (bindings) this formula has and the evaluator, which is the function of arity one, accepting the bindings as a keyword list and returning the result of this formula application.

## Functions

Returns the binding this formula requires.

Revalidates the formula with bindings given. Returns true if the formula strictly evaluates to `true`, `false` otherwise. Compiles the formula before evaluation if needed.

Generated clauses for `n ∈ [1..42]` to be used with dynamic number

Compiles the formula into module.

Checks whether the formula was already compiled into module.

Curries the formula by substituting the known bindings into it.

Evaluates the formula returning the result back.

Evaluates normalized representation of formula.

normalize(input) deprecated

Returns a normalized representation for the formula given.

Generated clauses for `n ∈ [1..12]` to be used with dynamic number

Purges and discards the module for the formula given (if exists.)

Produces the normalized representation of formula. If the rho is an instance of `Integer` or `Float`, it’s left intact, otherwise it’s moved to the left side with negation.

# t()

View Source

## Specs

```t() :: %atom(){
formula: binary(),
ast: nil | tuple(),
module: nil | atom(),
variables: nil | [atom()],
eval: nil | (keyword() -> any())
}```

The formulae is internally represented as struct, exposing the original binary representing the formula, AST, the module this formula was compiled into, variables (bindings) this formula has and the evaluator, which is the function of arity one, accepting the bindings as a keyword list and returning the result of this formula application.

# bindings?(formula, bindings \\ [])

View Source
This function is deprecated. Use `Formulae.compile/1` and `%Formulae{}.variables` or `Formula.curry/2` instead.

## Specs

```bindings?(formula :: t() | binary() | tuple(), binding :: keyword()) ::
keyword()```

Returns the binding this formula requires.

## Examples

``````iex> "a > 5" |> Formulae.bindings?
~w|a|a

iex> ":math.sin(a / (3.14 * b)) > c" |> Formulae.bindings?
~w|a b c|a

iex> "a + b * 4 - :math.pow(c, 2) / d > 1.0 * e" |> Formulae.bindings?
~w|a b c d e|a``````

# check(string, bindings \\ [])

View Source
This function is deprecated. Use `Formulae.eval/2` instead.

## Specs

`check(string :: binary(), bindings :: keyword()) :: boolean()`

Revalidates the formula with bindings given. Returns true if the formula strictly evaluates to `true`, `false` otherwise. Compiles the formula before evaluation if needed.

# combinations(l, n)

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## Specs

`combinations(list :: list(), count :: non_neg_integer()) :: [list()]`

Generated clauses for `n ∈ [1..42]` to be used with dynamic number

# compile(input)

View Source

## Specs

`compile(t() | binary()) :: t()`

Compiles the formula into module.

Examples:

``````iex> f = Formulae.compile("rem(a, 5) - b == 0")
iex> f.formula
"rem(a, 5) - b == 0"
iex> f.variables
[:a, :b]
iex> f.module
:"Elixir.Formulae.rem(a, 5) - b == 0"
iex> f.module.eval(a: 12, b: 2)
true

iex> f = Formulae.compile("rem(a, 5) + b == a")
iex> f.variables
[:a, :b]
iex> f.eval.(a: 7, b: 5)
true
iex> f.eval.(a: 7, b: 0)
false``````

# compiled?(input)

View Source

## Specs

`compiled?(binary() | t()) :: boolean()`

Checks whether the formula was already compiled into module.

Typically one does not need to call this function, since this check would be nevertheless transparently performed before the evaluation.

Examples:

``````iex> Formulae.compiled?("foo > 42")
false
iex> Formulae.compile("foo > 42")
iex> Formulae.compiled?("foo > 42")
true``````

# curry(input, binding \\ [], opts \\ [])

View Source

## Specs

`curry(input :: t() | binary(), binding :: keyword(), opts :: keyword()) :: t()`

Curries the formula by substituting the known bindings into it.

## Example

``````iex> Formulae.curry("(temp - foo * 4) > speed / 3.14", temp: 7, speed: 3.14).formula
"7 - foo * 4 > 3.14 / 3.14"``````

# eval(string, bindings \\ [])

View Source

## Specs

`eval(string :: binary(), bindings :: keyword()) :: term()`

Evaluates the formula returning the result back.

Examples:

``````iex> Formulae.eval("rem(a, 5) + rem(b, 4) == 0", a: 20, b: 20)
true
iex> Formulae.eval("rem(a, 5) == 0", a: 21)
false
iex> Formulae.eval("rem(a, 5) + rem(b, 4)", a: 21, b: 22)
3``````

# evaluate(input, binding \\ [], opts \\ [])

View Source
This function is deprecated. Use `Formulae.eval/2` instead.

## Specs

```evaluate(input :: binary() | tuple(), binding :: keyword(), opts :: keyword()) ::
boolean() | no_return()```

Evaluates normalized representation of formula.

## Examples

``````iex> Formulae.evaluate(Formulae.unit("3 > 2"))
true

iex> Formulae.evaluate(Formulae.unit("3 < 2"))
false

iex> Formulae.evaluate(Formulae.unit("a < 2"), [a: 1])
true

iex> Formulae.evaluate(Formulae.unit("a > 2"), [a: 1])
false

iex> Formulae.evaluate(Formulae.unit("a < 2"), [])
** (Formulae.RunnerError) Formula failed to run (compile): incomplete binding to evaluate a formula, lacking: [:a].

iex> Formulae.evaluate(Formulae.unit("a + 2 = 3"), [a: 1])
true

iex> Formulae.evaluate(Formulae.unit("a + 2 = 3"), [a: 2])
false

iex> Formulae.evaluate(Formulae.unit(~S|a = "3"|), [a: "3"])
true

iex> Formulae.evaluate(Formulae.unit(~S|a = "3"|), [a: 3])
false

iex> Formulae.evaluate(Formulae.unit(~S|a = "3"|), [a: "hello"])
false

iex> Formulae.evaluate("a + 2 = 3", [a: 2])
false

iex> Formulae.evaluate(~S|a = "3"|, [a: "3"])
true

iex> Formulae.evaluate(Formulae.unit("a_b_c_490000 > 2"), [a_b_c_490000: 3])
true``````

# normalize(input)

View Source
This function is deprecated. Use `Formulae.compile/1` and `%Formulae{}.variables` instead.

Returns a normalized representation for the formula given.

# permutations(l, n)

View Source

## Specs

`permutations(list :: list(), count :: non_neg_integer()) :: [list()]`

Generated clauses for `n ∈ [1..12]` to be used with dynamic number

# purge(input)

View Source

## Specs

`purge(t() | binary()) :: :ok | {:error, :not_compiled} | {:error, :code_delete}`

Purges and discards the module for the formula given (if exists.)

# unit(input, env \\ [])

View Source
This function is deprecated. Use `Formulae.eval/2` instead.

Produces the normalized representation of formula. If the rho is an instance of `Integer` or `Float`, it’s left intact, otherwise it’s moved to the left side with negation.

## Examples

``````iex> Formulae.unit("3 > 2")
{"3 > 2", {:>, [], [3, 2]}}

iex> Formulae.unit("3 - a > 2")
{"3 - a > 2", {:>, [], [{:-, [line: 1], [3, {:a, [line: 1], nil}]}, 2]}}

iex> Formulae.unit("3 > A + 2")
{"3 > a + 2",
{:>, [],
[{:-, [context: Formulae, import: Kernel],
[3, {:+, [line: 1], [{:a, [line: 1], nil}, 2]}]}, 0]}}

iex> Formulae.unit("3 >= a + 2")
{"3 >= a + 2",
{:>=, [],
[{:-, [context: Formulae, import: Kernel],
[3, {:+, [line: 1], [{:a, [line: 1], nil}, 2]}]}, 0]}}

iex> Formulae.unit("3 a > A + 2")
** (Formulae.SyntaxError) Formula [3 a > A + 2] syntax is incorrect (parsing): syntax error before: “a”.

iex> Formulae.unit("a + 2 = 3")
{"a + 2 = 3", {:==, [], [{:+, [line: 1], [{:a, [line: 1], nil}, 2]}, 3]}}

iex> Formulae.unit(~S|A = "3"|)
{"a = \"3\"", {:==, [], [{:a, [line: 1], nil}, "3"]}}``````