Add if expressions

src/expression.rs

@@ -1,6 +1,6 @@
 use std::str::FromStr;
 
-use crate::{env::Env, function::FunctionMap, value::Value};
+use crate::{env::Env, function::FunctionMap, statement::Statement, value::Value};
 
 #[derive(Debug, Clone, Copy, PartialEq, Eq)]
 pub enum BinaryOperation {
@@ -38,13 +38,17 @@ impl FromStr for BinaryOperation {
     }
 }
 
-#[derive(Debug, Clone, PartialEq, Eq)]
+#[derive(Debug, Clone, PartialEq)]
 pub enum Expression {
     Constant(Value),
     Variable(String),
     Call(String, Vec<Expression>),
     CallMethod(Box<Expression>, String, Vec<Expression>),
     Binary(Box<Expression>, BinaryOperation, Box<Expression>),
+    If(
+        Vec<(Expression, Statement, Expression)>,
+        (Box<Statement>, Box<Expression>),
+    ),
 }
 
 impl Expression {
@@ -89,6 +93,19 @@ impl Expression {
                     BinaryOperation::NotEqual => (lhs != rhs).into(),
                 }
             }
+            Expression::If(ifs, (else_statement, else_expr)) => {
+                for (expr, statement, ret) in ifs {
+                    let e = Env::new_with_parent(e);
+                    if expr.eval(&e, f).is_truthy() {
+                        statement.eval(&e, f);
+                        return ret.eval(&e, f);
+                    }
+                }
+
+                let e = Env::new_with_parent(e);
+                else_statement.eval(&e, f);
+                else_expr.eval(&e, f)
+            }
         }
     }
 }

src/grammar.pest

@@ -38,7 +38,7 @@ value = { (const_value | call | identifier | parens) ~ method_call }
 
 method_call = { (("." ~ identifier ~ call_params) ~ method_call)? }
 
-expression = { equality }
+expression = { if_block_expr | equality }
 
 equality = { inequality ~ ((equals | not_equals) ~ inequality)? }
 
@@ -67,6 +67,10 @@ while_block = { "while" ~ expression ~ block }
 
 if_block = { "if" ~ expression ~ block ~ ("else if" ~ expression ~ block)* ~ ("else" ~ block)? }
 
+if_block_expr = { "if" ~ expression ~ if_block_expr_block ~ ("else if" ~ expression ~ if_block_expr_block)* ~ "else" ~ if_block_expr_block }
+
+if_block_expr_block = { "{" ~ statement* ~ expression ~ "}" }
+
 def_params = { "(" ~ (identifier ~ ","?)* ~ ")" }
 
 def = { "def" ~ identifier ~ def_params ~ func_block }

src/main.rs

@@ -50,11 +50,11 @@ impl CustomValue for Foo {
         }
     }
 
-fn functions(&self) -> Option<FunctionMap> {
-    let mut map = FunctionMap::new();
-    map.insert_native("edit_foo", Foo::edit);
-    Some(map)
-}
+    fn functions(&self) -> Option<FunctionMap> {
+        let mut map = FunctionMap::new();
+        map.insert_native("edit_foo", Foo::edit);
+        Some(map)
+    }
 }
 
 fn main() {

src/pest_parser.rs

@@ -189,6 +189,36 @@ fn parse_expression(pair: Pair<Rule>) -> Expression {
                 v
             }
         }
+        Rule::if_block_expr => {
+            let mut inner = pair.into_inner();
+            let mut the_list = vec![];
+            let mut the_else = None;
+            while let Some(expr) = inner.next() {
+                if let Some(if_block) = inner.next() {
+                    let expr = parse_expression(expr);
+                    let if_block_body = if_block.into_inner();
+                    let (a, b): (Vec<_>, Vec<_>) =
+                        if_block_body.partition(|a| a.as_rule() == Rule::statement);
+                    let (statements, _): (_, FuncHolder) =
+                        a.into_iter().map(parse_statement).unzip();
+                    let z = b.into_iter().map(parse_expression).collect::<Vec<_>>();
+                    the_list.push((expr, Statement::Body(statements), z[0].clone()));
+                } else {
+                    let if_block_body = expr.into_inner();
+                    let (a, b): (Vec<_>, Vec<_>) =
+                        if_block_body.partition(|a| a.as_rule() == Rule::statement);
+                    let (statements, _): (_, FuncHolder) =
+                        a.into_iter().map(parse_statement).unzip();
+                    let z = b.into_iter().map(parse_expression).collect::<Vec<_>>();
+                    the_else = Some((
+                        Box::new(Statement::Body(statements)),
+                        Box::new(z[0].clone()),
+                    ));
+                }
+            }
+
+            Expression::If(the_list, the_else.unwrap())
+        }
         _ => unreachable!(),
     }
 }

test.foo

@@ -25,3 +25,11 @@ print(x);
 
 print(add_one(41));
 
+let x = 0;
+if x == 0 {
+    x = x + 10;
+}
+print(x);
+
+let x = 5;
+print(if x < 10 { 20 } else { 30 });