File operations

* read
* write
* append
* exists?
* tests for each

tests/test_lib_file.rs

@@ -0,0 +1,80 @@
+mod file_lib_tests {
+    use relish::ast::{eval, lex, SymTable};
+    use relish::stdlib::{dynamic_stdlib, static_stdlib};
+
+    #[test]
+    fn test_fexists() {
+        let document = "(exists? '/tmp')";
+        let result = "true";
+
+        let mut syms = SymTable::new();
+        static_stdlib(&mut syms);
+        dynamic_stdlib(&mut syms, None);
+        assert_eq!(
+            *eval(&lex(&document.to_string()).unwrap(), &mut syms)
+                .unwrap()
+                .to_string(),
+            result.to_string(),
+        );
+    }
+
+    #[test]
+    fn test_fexists_doesnt() {
+        let document = "(exists? 'cargo.timtam')";
+        let result = "false";
+
+        let mut syms = SymTable::new();
+        static_stdlib(&mut syms);
+        dynamic_stdlib(&mut syms, None);
+        assert_eq!(
+            *eval(&lex(&document.to_string()).unwrap(), &mut syms)
+                .unwrap()
+                .to_string(),
+            result.to_string(),
+        );
+    }
+
+    #[test]
+    fn test_write_file() {
+        let document = "
+          (let ((s 'test')
+                (t '/tmp/relish-lib-test-file-1'))
+            (write-file t s)
+            (echo (read-file t))
+            (eq? (read-file t) s))";
+        let result = "true";
+
+        let mut syms = SymTable::new();
+        static_stdlib(&mut syms);
+        dynamic_stdlib(&mut syms, None);
+        assert_eq!(
+            *eval(&lex(&document.to_string()).unwrap(), &mut syms)
+                .unwrap()
+                .to_string(),
+            result.to_string(),
+        );
+    }
+
+    #[test]
+    fn test_append_file() {
+        let document = "
+          (let ((s 'test')
+                (t '/tmp/relish-lib-test-file-2'))
+            (write-file t s)
+            (append-file t s)
+            (eq? (read-file t)
+                (concat s s)))";
+        let result = "true";
+
+        let mut syms = SymTable::new();
+        static_stdlib(&mut syms);
+        dynamic_stdlib(&mut syms, None);
+        assert_eq!(
+            *eval(&lex(&document.to_string()).unwrap(), &mut syms)
+                .unwrap()
+                .to_string(),
+            result.to_string(),
+        );
+    }
+
+}