reval 0.4.5

Simple Rust expression evaluator
Documentation 
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use super::BoxedFunction;
use crate::{Error, Result};
use std::collections::HashMap;

/// Stores user-functions so they can be easilly called
#[derive(Default)]
pub struct UserFunctions {
    functions: HashMap<&'static str, BoxedFunction>,
}

impl UserFunctions {
    /// Get a userfunction by name
    pub fn get(&self, name: &str) -> Result<&BoxedFunction> {
        self.functions
            .get(name)
            .ok_or_else(|| Error::UnknownUserFunction(name.to_owned()))
    }

    /// Add a user-function to the collection
    pub fn add_function(&mut self, function: BoxedFunction) {
        // TODO: Check if function name is valid
        self.functions.insert(function.name(), function);
    }

    pub fn add_functions<I: IntoIterator<Item = BoxedFunction>>(&mut self, functions: I) {
        for function in functions {
            self.add_function(function);
        }
    }

    /// Merge two sets of user-functions
    pub fn merge(&mut self, functions: UserFunctions) -> &mut Self {
        self.functions.extend(functions.functions.into_iter());
        self
    }
}