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-rw-r--r--third_party/rust/nom/tests/arithmetic.rs94
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
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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)));
+}