Parse till operators

src/grammars/mblf.pest

@@ -1 +1,15 @@
-alpha = { 'a'..'z' | 'A'..'Z' }
+operator = @{ "operator" } // TODO
+operand = @{ "operand" }  // TODO
+
+instruction = { operator ~ (" "+ ~ operand)*}
+
+loopBlockStart = {  "[" }
+loopBlockEnd = { "]" }
+loopBlock = { loopBlockStart
+            ~ instruction*
+            ~ loopBlockEnd
+}
+
+statement = _{ instruction | loopBlock }
+
+file = {SOI ~ (statement ~ ("\n" | "\r\n")+)* ~ EOI}

src/main.rs

@@ -8,6 +8,7 @@ extern crate pest;
 #[macro_use]
 extern crate pest_derive;
 
+use pest::iterators::Pair;
 use pest::Parser;
 
 #[derive(Parser)]
@@ -23,20 +24,55 @@ struct Cli {
     output_file: std::path::PathBuf,
 }
 
+fn instruct(statement: Pair<Rule>, mut out: &File) {
+    match statement.as_rule() {
+        Rule::instruction => {
+            for nested_statement in statement.into_inner() {
+                instruct(nested_statement, out);
+            }
+            out.write(b"\n");
+        }
+        Rule::operator => {
+            out.write(b"operator ");
+        }
+        Rule::operand => {
+            out.write(b"operand ");
+        }
+
+        Rule::loopBlock => {
+            for nested_statement in statement.into_inner() {
+                instruct(nested_statement, out);
+            }
+        }
+        Rule::loopBlockStart => {
+            out.write(b"loopBlockStart\n");
+        }
+        Rule::loopBlockEnd => {
+            out.write(b"loopBlockEnd\n");
+        }
+        Rule::EOI => {
+            out.write(b"\n");
+        }
+        _ => unreachable!(),
+    }
+}
+
 fn main() -> Result<(), Box<dyn std::error::Error>> {
     let args = Cli::from_args();
 
     let content = std::fs::read_to_string(&args.input_file)
         .with_context(|| format!("could not read source file {:?}", args.input_file))?;
 
-    let mut out = File::create(args.output_file)?;
-
-    let _pairs = MblfParser::parse(Rule::alpha, "a").unwrap();
-
-
+    let out = File::create(args.output_file)?;
 
+    let parsed_file = MblfParser::parse(Rule::file, &content)
+        .expect("Parse Error")
+        .next()
+        .unwrap();
 
-    out.write_all(&content.as_bytes())?;
+    for statement in parsed_file.into_inner() {
+        instruct(statement, &out);
+    }
 
     out.sync_all()?;