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Add nicer handle_builtin method

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greg 2017-01-05 04:12:05 -08:00
parent 6741787852
commit 154839979b
1 changed files with 18 additions and 16 deletions
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34
src/eval.rs
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@ -5,6 +5,9 @@ use std::collections::VecDeque;
use parser::{AST, Statement, Expression, Function};
use std::rc::Rc;
use parser::Expression::*;
use parser::Statement::*;
type Reduction<T> = (T, Option<SideEffect>);
#[derive(Debug)]
@ -70,7 +73,6 @@ trait Evaluable {
impl Evaluable for Statement {
fn is_reducible(&self) -> bool {
use parser::Statement::*;
match self {
&ExprNode(ref expr) => expr.is_reducible(),
&FuncDefNode(_) => true,
@ -80,7 +82,6 @@ impl Evaluable for Statement {
impl Evaluable for Expression {
fn is_reducible(&self) -> bool {
use parser::Expression::*;
match *self {
Null => false,
StringLiteral(_) => false,
@ -93,7 +94,6 @@ impl Evaluable for Expression {
impl Expression {
fn is_truthy(&self) -> bool {
use parser::Expression::*;
match *self {
Null => false,
StringLiteral(ref s) if **s == "" => false,
@ -136,7 +136,6 @@ impl<'a> Evaluator<'a> {
}
fn reduce_astnode(&mut self, node: Statement) -> Reduction<Statement> {
use parser::Statement::*;
match node {
ExprNode(expr) => {
if expr.is_reducible() {
@ -154,7 +153,6 @@ impl<'a> Evaluator<'a> {
}
fn reduce_expr(&mut self, expression: Expression) -> Reduction<Expression> {
use parser::Expression::*;
match expression {
Null => (Null, None),
e @ StringLiteral(_) => (e, None),
@ -251,7 +249,6 @@ impl<'a> Evaluator<'a> {
}
fn reduce_binop(&mut self, op: Rc<String>, left: Expression, right: Expression) -> Expression {
use parser::Expression::*;
let truthy = Number(1.0);
let falsy = Null;
match (&op[..], left, right) {
@ -274,16 +271,8 @@ impl<'a> Evaluator<'a> {
}
fn reduce_call(&mut self, name: Rc<String>, arguments: Vec<Expression>) -> Reduction<Expression> {
use parser::Expression::*;
use parser::Statement::*;
// ugly hack for now
if *name == "print" {
let mut s = String::new();
for arg in arguments {
s.push_str(&format!("{} ", arg));
}
return (Null, Some(SideEffect::Print(s)));
if let Some(res) = handle_builtin(&*name, &arguments) {
return res;
}
let function = match self.lookup_function(&*name) {
@ -313,3 +302,16 @@ impl<'a> Evaluator<'a> {
}
}
}
fn handle_builtin(name: &str, arguments: &Vec<Expression>) -> Option<Reduction<Expression>> {
match name {
"print" => {
let mut s = String::new();
for arg in arguments {
s.push_str(&format!("{} ", arg));
}
return Some((Null, Some(SideEffect::Print(s))));
},
_ => None
}
}