Struct wlambda::compiler::GlobalEnv

pub struct GlobalEnv { /* fields omitted */ }

Holds global environment variables.

This data structure is part of the API. It's there to make functions or values available to a WLambda program.

This environment structure is usually wrapped inside an EvalContext which augments it for calling the compiler and allows evaluation of the code.

See also:

• GlobalEnv::add_func() of how to create a function and put it into the global variable.
• And GlobalEnv::set_module() of how to supply your own importable modules. See also SymbolTable has a good example how that could work.
• And GlobalEnv::set_var().
• And GlobalEnv::get_var().

Methods

impl GlobalEnv

pub fn add_func<T>(
    &mut self,
    fnname: &str,
    fun: T,
    min_args: Option<usize>,
    max_args: Option<usize>
) where
    T: 'static + Fn(&mut Env, usize) -> Result<VVal, StackAction>, 

Adds a function to a GlobalEnv.

This is an example of how to add a function:

use wlambda::compiler::GlobalEnv;
use wlambda::vval::{Env, VVal};

let g = GlobalEnv::new();
g.borrow_mut().add_func(
    "push",
    |env: &mut Env, argc: usize| {
        if argc < 2 { return Ok(VVal::Nul); }
        let v = env.arg(0);
        v.push(env.arg(1).clone());
        Ok(v.clone())
    }, Some(2), Some(2));

pub fn set_var(&mut self, var: &str, val: &VVal)

Sets a global variable to a value.

See also EvalContext::set_global_var()

pub fn get_var(&mut self, var: &str) -> Option<VVal>

Returns the value of a global variable.

See also EvalContext::get_global_var()

pub fn set_module(&mut self, mod_name: &str, symtbl: SymbolTable)

Sets a symbol table for a module before a module asks for it. Modules set via this function have precedence over resolved modules via set_resolver().

Here is an example how to setup your own module:

 use wlambda::{VVal, EvalContext, GlobalEnv, SymbolTable};

 let my_mod = SymbolTable::new();

pub fn import_module_as(&mut self, mod_name: &str, prefix: &str)

Imports all symbols from the designated module with the specified prefix applied. This does not call out to the resolver and only works on previously set_module modules.

pub fn set_resolver(&mut self, res: Rc<RefCell<dyn ModuleResolver>>)

Sets the module resolver. There is a LocalFileModuleResolver available which loads the modules relative to the current working directory.

Please note that modules made available using set_module have priority over modules that are provided by the resolver.

 use std::rc::Rc;
 use std::cell::RefCell;

 let global = wlambda::compiler::GlobalEnv::new_default();

 let lfmr = Rc::new(RefCell::new(
     wlambda::compiler::LocalFileModuleResolver::new()));

 global.borrow_mut().set_resolver(lfmr);

pub fn new() -> GlobalEnvRef

Creates a new completely empty GlobalEnv.

There is no core language, no std lib. You have to add all that on your own via set_var and set_module.

pub fn new_default() -> GlobalEnvRef

Returns a default global environment. Where default means what the author of WLambda decided what is default at the moment. For more precise global environment, that is not a completely moving target consider the alternate constructor variants.

Global environments constructed with this typically contain:

• set_module("wlambda", wlambda::prelude::core_symbol_table())
• set_module("std", wlambda::prelude::std_symbol_table())
• set_resolver(Rc::new(RefCell::new(wlambda::compiler::LocalFileModuleResolver::new()))
• import_module_as("wlambda", "")
• import_module_as("std", "std")

On top of that, the WLambda module has been imported without a prefix and the std module has been loaded with an std: prefix. This means you can load and eval scripts you see all over this documentation.

pub fn import_modules_from(&mut self, parent_global_env: &GlobalEnv)

This function adds the modules that were loaded into memory from the given parent_global_env to the current environment.

pub fn new_empty_default() -> GlobalEnvRef

This is like new_default but does not import anything, neither the core language nor the std module.

Trait Implementations

impl Clone for GlobalEnv

fn clone(&self) -> GlobalEnv

Returns a copy of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for GlobalEnv

fn fmt(&self, f: &mut Formatter) -> Result

Formats the value using the given formatter.