Support empty conditionals, assignment, variable declarations, ident-as-value

forge-script-lang/src/parser/ast.rs

@@ -18,7 +18,18 @@ pub struct ExpressionList {
 	pub expressions: Vec<Expression>,
 	pub is_void: bool,
 }
+impl Default for ExpressionList {
+	fn default() -> Self {
+		ExpressionList::empty()
+	}
+}
 impl ExpressionList {
+	pub fn empty() -> Self {
+		ExpressionList {
+			expressions: Vec::new(),
+			is_void: true,
+		}
+	}
 	pub fn production(expressions: Vec<Expression>) -> Self {
 		ExpressionList {
 			expressions,
@@ -155,6 +166,7 @@ pub enum ValueExpression {
 	DeclareIdentifier(DeclareIdent),
 	Assignment(Assignment),
 	ConditionalBlock(Conditional),
+	Identifier(Identifier),
 }
 
 #[derive(Clone)]

forge-script-lang/src/parser/grammar.rs

@@ -29,19 +29,26 @@ peg::parser! {
 		rule value_expression() -> ValueExpression
 			= "(" ex:value_expression() ")" { ValueExpression::Grouped(GroupedExpression { inner: Box::new(ex) }) }
 			/ co:conditional() { ValueExpression::ConditionalBlock(co) }
+			/ decl:declare_variable() { ValueExpression::DeclareIdentifier(decl) }
 			/ left:value_expression() op:binary_operator() right:value_expression()
 				{ ValueExpression::Binary { lhs: Box::new(left), rhs: Box::new(right), operator: op } }
 			/ op:unary_operator() operand:value_expression()
 				{ ValueExpression::Unary { operator: op, operand: Box::new(operand) } }
+			/ ident:bare_identifier() { ValueExpression::Identifier(ident) }
 			/ li:literal() { ValueExpression::Literal(li) }
 
 		rule print() -> Print
 			= "print" ex:value_expression() { ex.into() }
 
+		rule declare_variable() -> DeclareIdent
+			= "let" assign:assignment() { DeclareIdent::WithValue(assign) }
+			/ "let" ident:bare_identifier() { DeclareIdent::WithoutValue(ident) }
+
 		rule condition_loop() -> ConditionalLoop
-			= "while" guard:value_expression() "{" block:expression_list() "}" { ConditionalLoop { block: GuardedBlock { guard: Box::new(guard), block}, fallback: None } }
-			/ "while" guard:value_expression() "{" block:expression_list() "}" "else" "{" fallback:expression_list() "}"
-				{ ConditionalLoop { block: GuardedBlock { guard: Box::new(guard), block}, fallback: Some(fallback) } }
+			= "while" guard:value_expression() "{" block:expression_list()? "}"
+				{ ConditionalLoop { block: GuardedBlock { guard: Box::new(guard), block: block.unwrap_or_default() }, fallback: None } }
+			/ "while" guard:value_expression() "{" block:expression_list()? "}" "else" "{" fallback:expression_list()? "}"
+				{ ConditionalLoop { block: GuardedBlock { guard: Box::new(guard), block: block.unwrap_or_default() }, fallback } }
 
 		rule conditional() -> Conditional
 			// = bl:guarded_block() { Conditional { fallback: None, blocks: vec![bl] } }
@@ -54,8 +61,11 @@ peg::parser! {
 			/ blocks:(guarded_block() ++ "else") { Conditional { fallback: None, blocks, } }
 
 		rule guarded_block() -> GuardedBlock
-			= "if" guard:value_expression() "{" block:expression_list() "}"
-				{ GuardedBlock { block, guard: Box::new(guard) } }
+			= "if" guard:value_expression() "{" block:expression_list()? "}"
+				{ GuardedBlock { block: block.unwrap_or_default(), guard: Box::new(guard) } }
+
+		rule assignment() -> Assignment
+			= ident:bare_identifier() "=" expr:value_expression() { Assignment { ident, value: Box::new(expr) } }
 
 		rule binary_operator() -> BinaryOp
 			= "+" { BinaryOp::Add }

forge-script-lang/src/runtime/executor/printer.rs

@@ -140,6 +140,9 @@ impl Visitor for TreePrinter {
 				self.evaluate_value_expression(inner.as_ref());
 				self.write(")");
 			}
+			ValueExpression::Identifier(ident) => {
+				self.write(ident);
+			}
 		}
 	}