1 files changed, 94 insertions, 0 deletions
diff --git a/third_party/rust/nom/tests/arithmetic.rs b/third_party/rust/nom/tests/arithmetic.rs
new file mode 100644
index 0000000000..5b627a97a5
--- /dev/null
+++ b/third_party/rust/nom/tests/arithmetic.rs
@@ -0,0 +1,94 @@
+use nom::{
+  branch::alt,
+  bytes::complete::tag,
+  character::complete::char,
+  character::complete::{digit1 as digit, space0 as space},
+  combinator::map_res,
+  multi::fold_many0,
+  sequence::{delimited, pair},
+  IResult,
+};
+
+// Parser definition
+
+use std::str::FromStr;
+
+// We parse any expr surrounded by parens, ignoring all whitespaces around those
+fn parens(i: &str) -> IResult<&str, i64> {
+  delimited(space, delimited(tag("("), expr, tag(")")), space)(i)
+}
+
+// We transform an integer string into a i64, ignoring surrounding whitespaces
+// We look for a digit suite, and try to convert it.
+// If either str::from_utf8 or FromStr::from_str fail,
+// we fallback to the parens parser defined above
+fn factor(i: &str) -> IResult<&str, i64> {
+  alt((
+    map_res(delimited(space, digit, space), FromStr::from_str),
+    parens,
+  ))(i)
+}
+
+// We read an initial factor and for each time we find
+// a * or / operator followed by another factor, we do
+// the math by folding everything
+fn term(i: &str) -> IResult<&str, i64> {
+  let (i, init) = factor(i)?;
+
+  fold_many0(
+    pair(alt((char('*'), char('/'))), factor),
+    move || init,
+    |acc, (op, val): (char, i64)| {
+      if op == '*' {
+        acc * val
+      } else {
+        acc / val
+      }
+    },
+  )(i)
+}
+
+fn expr(i: &str) -> IResult<&str, i64> {
+  let (i, init) = term(i)?;
+
+  fold_many0(
+    pair(alt((char('+'), char('-'))), term),
+    move || init,
+    |acc, (op, val): (char, i64)| {
+      if op == '+' {
+        acc + val
+      } else {
+        acc - val
+      }
+    },
+  )(i)
+}
+
+#[test]
+fn factor_test() {
+  assert_eq!(factor("3"), Ok(("", 3)));
+  assert_eq!(factor(" 12"), Ok(("", 12)));
+  assert_eq!(factor("537  "), Ok(("", 537)));
+  assert_eq!(factor("  24   "), Ok(("", 24)));
+}
+
+#[test]
+fn term_test() {
+  assert_eq!(term(" 12 *2 /  3"), Ok(("", 8)));
+  assert_eq!(term(" 2* 3  *2 *2 /  3"), Ok(("", 8)));
+  assert_eq!(term(" 48 /  3/2"), Ok(("", 8)));
+}
+
+#[test]
+fn expr_test() {
+  assert_eq!(expr(" 1 +  2 "), Ok(("", 3)));
+  assert_eq!(expr(" 12 + 6 - 4+  3"), Ok(("", 17)));
+  assert_eq!(expr(" 1 + 2*3 + 4"), Ok(("", 11)));
+}
+
+#[test]
+fn parens_test() {
+  assert_eq!(expr(" (  2 )"), Ok(("", 2)));
+  assert_eq!(expr(" 2* (  3 + 4 ) "), Ok(("", 14)));
+  assert_eq!(expr("  2*2 / ( 5 - 1) + 3"), Ok(("", 4)));
+}