add string split method

src/stl.rs

@@ -74,6 +74,17 @@ pub fn static_stdlib(syms: &mut SymTable) -> Result<(), String> {
         },
     );
 
+    syms.insert(
+        "split".to_string(),
+        Symbol {
+            name: String::from("split"),
+            args: Args::Strict(vec![Type::String, Type::String]),
+            conditional_branches: false,
+            docs: strings::SPLIT_DOCSTRING.to_string(),
+            value: ValueType::Internal(Rc::new(strings::split_callback)),
+        },
+    );
+
     syms.insert(
         "strlen".to_string(),
         Symbol {

src/stl/strings.rs

@@ -115,3 +115,36 @@ pub fn contains_callback(ast: &Seg, _syms: &mut SymTable) -> Result<Ctr, String>
 
     Ok(Ctr::Bool(parent_str.contains(&child_str)))
 }
+
+pub const SPLIT_DOCSTRING: &str = "Takes two strings. String 1 is a source string and string 2 is a delimiter.
+Returns a list of substrings from string 1 that were found delimited by string 2.";
+
+pub fn split_callback(ast: &Seg, _syms: &mut SymTable) -> Result<Ctr, String> {
+    let parent_str: String;
+    if let Ctr::String(ref s) = *ast.car {
+        parent_str = s.to_string();
+    } else {
+        return Err("first argument must be a string".to_string());
+    }
+
+    let second_arg_obj: &Ctr;
+    let delim_str: String;
+    if let Ctr::Seg(ref s) = *ast.cdr {
+        second_arg_obj = &*s.car;
+    } else {
+        return Err("impossible error: needs two arguments".to_string());
+    }
+
+    if let Ctr::String(ref s) = &*second_arg_obj {
+        delim_str = s.clone();
+    } else {
+        return Err("second argument must be a string".to_string());
+    }
+
+    let mut ret = Seg::new();
+    for substr in parent_str.split(&delim_str) {
+        ret.append(Box::new(Ctr::String(substr.to_string())));
+    }
+
+    Ok(Ctr::Seg(ret))
+}