chap 2.5.0

Chap is an easy to learn, interpretive, scripting language written in Rust
Documentation 
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use crate::builtin_function::utils::{param_to_datatype, returns};
use crate::common::data_type::DataType;
use crate::common::errors::{ChapError, Result};
use crate::{common::executable::ExecutableLine, runtime::Runtime};

pub fn get(runtime: &mut Runtime, executable: &ExecutableLine) -> Result<()> {
    let p1 = param_to_datatype(runtime, executable.params.first(), executable.line_number)?;
    let p2 = param_to_datatype(runtime, executable.params.get(1), executable.line_number)?;

    match (p1, p2) {
        (DataType::List(list), DataType::Int(index)) => {
            if let Ok(x) = usize::try_from(*index) {
                if x == 0 {
                    return Err(ChapError::runtime_with_msg(
                        executable.line_number,
                        "list index starts from 1".to_string(),
                    ));
                }
                let x = x - 1;
                let value = list.get(x);
                if let Some(value) = value {
                    returns(runtime, executable, value.clone())
                } else {
                    Err(ChapError::runtime_with_msg(
                        executable.line_number,
                        "index out of bound".to_string(),
                    ))
                }
            } else {
                Err(ChapError::runtime_with_msg(
                    executable.line_number,
                    "negative index".to_string(),
                ))
            }
        }
        (DataType::Map(map), DataType::String(key)) => {
            let value = map.get(key);

            if let Some(value) = value {
                returns(runtime, executable, value.clone())
            } else {
                Err(ChapError::runtime_with_msg(
                    executable.line_number,
                    "key not found".to_string(),
                ))
            }
        }
        _ => Err(ChapError::runtime_with_msg(
            executable.line_number,
            "correct form of 'get' function: <list | map>, <index | key> -> get -> $item"
                .to_string(),
        )),
    }
}