Struct Context

pub struct Context {
    pub prev_ans: Option<f64>,
    /* private fields */
}

Object passed to the calculate() function to track state of the calculator, including defined variables, functions, and equation history

Fields

prev_ans: Option<f64>

Stores the value of the last successful calculation result, used when evaluating the ans builtin variable;

Implementations

impl Context

pub fn new() -> Self

pub fn lookup_var(&self, query: &String) -> Option<Result<f64, CalcError>>

Takes in a query string and returns an Option that is none if the variable doesn’t exist in the var table. The option contains a result that will be Ok with the var’s value if the var can be read from, otherwise an error.

pub fn try_function( &self, name: &String, args: Vec<f64>, ) -> Option<Result<f64, CalcError>>

This function looks up a function with the specified name, returning a None Option if the function doesn’t exist, an Err inside the Option if there’s an issue with the arguments, otherwise it executes the function with the given arguments and returns the answer

pub fn assign_var(&mut self, query: &String, val: f64) -> Result<(), CalcError>

This function triest to assign a value to variable, returning an empty Ok if successful, otherwise an Err