Adding transitions support

src/rsprocess/transitions.rs

@@ -0,0 +1,58 @@
+#![allow(dead_code)]
+
+use std::rc::Rc;
+use super::structure::{RSChoices, RSenvironment, RSprocess};
+
+pub fn unfold<'a>(environment: &'a RSenvironment<'a>, context_process: &'a RSprocess<'a>) -> Result<RSChoices<'a>, String> {
+    match context_process {
+	RSprocess::Nill => Ok(RSChoices::new()),
+	RSprocess::RecursiveIdentifier{identifier} => {
+	    let newprocess = environment.get(identifier);
+	    if let Some(newprocess) = newprocess {
+		unfold(environment, newprocess)
+	    } else {
+		Err(format!("Recursive call to missing symbol: {identifier}"))
+	    }
+	},
+	RSprocess::EntitySet{entities, next_process} => {
+	    Ok(RSChoices::from(vec![(Rc::new(entities.clone()), Rc::clone(next_process))]))
+	},
+	RSprocess::WaitEntity{repeat, repeated_process: _, next_process} if *repeat <= 0 => {
+	    unfold(environment, next_process)
+	},
+	RSprocess::WaitEntity{repeat, repeated_process, next_process} if *repeat == 1 => {
+	    let mut choices1 = unfold(environment, repeated_process)?;
+	    choices1.replace(Rc::clone(next_process));
+	    Ok(choices1)
+	},
+	RSprocess::WaitEntity{repeat, repeated_process, next_process} => {
+	    let mut choices1 = unfold(environment, repeated_process)?;
+	    choices1.replace(
+		Rc::new(
+		    RSprocess::WaitEntity{ repeat: (*repeat - 1),
+					   repeated_process: Rc::clone(repeated_process),
+					   next_process: Rc::clone(next_process) }
+		)
+	    );
+	    Ok(choices1)
+	},
+	RSprocess::Summation{children} => {
+	    // short-circuits with try_fold.
+	    children.iter().try_fold(RSChoices::new(), |mut acc, x| {
+		match unfold(environment, x) {
+		    Ok(mut choices) => {acc.append(&mut choices); Ok(acc)},
+		    Err(e) => Err(e)
+		}
+	    })
+	},
+	RSprocess::NondeterministicChoice{children} => {
+	    // short-circuits with try_fold.
+	    children.iter().try_fold(RSChoices::new(), |mut acc, x| {
+		match unfold(environment, x) {
+		    Ok(choices) => {acc.shuffle(choices); Ok(acc)},
+		    Err(e) => Err(e)
+		}
+	    })
+	}
+    }
+}