Add single-line comments

examples/test.psl

@@ -1,10 +1,31 @@
+// Vectors
+
 struct vec2:
 	x : f32
 	y : f32
 
-func add(a : vec2, b : vec2) -> qwe:
+func add(a : vec2, b : vec2) -> vec2:
 	return vec2(a.x + b.x, a.y + b.y)
 
 mut v = add(vec2(1.0, 2.0), vec2(3.0, 4.0))
 v.x = -v.x
 v.y = -v.y
+
+// Factorial
+
+func factorial(n : u32) -> u32:
+	if n == 0u:
+		return 1u
+	return n * factorial(n - 1u)
+
+let factorial10 = factorial(10u)
+
+// Fibonacci
+func fib(n : u32) -> u32:
+	// Slow implementation with
+	// exponentially-growing recursion tree
+	if n == 0u | n == 1u:
+		return n // base case
+	return fib(n - 1u) + fib(n - 2u)
+
+let fib10 = fib(10u)

libs/parser/rules/pslang.l

@@ -21,6 +21,8 @@ using bp = ::pslang::parser::bison::parser;
 
 [ ]+ { ctx.location.step(); }
 
+"//"[^\n]*  { return bp::make_comment(ctx.location); }
+
 const { return bp::make_const(ctx.location); }
 let   { return bp::make_let(ctx.location); }
 mut   { return bp::make_mut(ctx.location); }

libs/parser/rules/pslang.y

@@ -61,6 +61,7 @@ template <typename T>
 
 %token newline "newline"
 %token indent "indentation"
+%token comment
 %token assignment "="
 %token colon ":"
 %token comma ","
@@ -169,8 +170,8 @@ module
 ;
 
 indented_statement_list
-: indented_statement_list indentation statement newline { auto tmp = $1; tmp.statements.push_back({$2, std::make_unique<ast::statement>($3)}); $$ = std::move(tmp); }
-| indented_statement_list indentation newline { $$ = $1; }
+: indented_statement_list indentation statement optional_comment newline { auto tmp = $1; tmp.statements.push_back({$2, std::make_unique<ast::statement>($3)}); $$ = std::move(tmp); }
+| indented_statement_list indentation optional_comment newline { $$ = $1; }
 | %empty { $$ = {}; }
 ;
 
@@ -179,6 +180,11 @@ indentation
 | %empty { $$ = 0ull; }
 ;
 
+optional_comment
+: comment
+| %empty
+;
+
 statement
 : expression { $$ = std::make_unique<ast::expression>($1); }
 | expression assignment expression { $$ = ast::assignment{ std::make_unique<ast::expression>($1), std::make_unique<ast::expression>($3), @$ }; }