Github user jjmeyer0 commented on a diff in the pull request:
https://github.com/apache/metron/pull/814#discussion_r147556465
--- Diff: metron-stellar/stellar-common/README.md ---
@@ -100,6 +102,28 @@ In the core language functions, we support basic
functional programming primitiv
* `FILTER` - Filters a list by a predicate in the form of a lambda
expression. For instance `FILTER([ 'foo', 'bar'], (x ) -> x == 'foo' )`
returns `[ 'foo' ]`
* `REDUCE` - Applies a function over a list of input. For instance
`REDUCE([ 1, 2, 3], (sum, x) -> sum + x, 0 )` returns `6`
+### Stellar Language Match Expression
+
+Stellar provides the capability to write match expressions, which are
similar to switch statements commonly found in c like languages, but more like
+Scala's match.
+
+The syntax is:
+* `match{ logical_expression1 : evaluation expression1,
logical_expression2 : evaluation_expression2` : A match expression with no
default
+* `match{ logical_expression1 : evaluation expression1,
logical_expression2 : evaluation_expression2, default : default_expression}` :
A match expression with a default expression
+
+Where:
+
+* `logical_expression` is a Stellar expression that evaluates to true or
false. For instance `var > 0` or `var > 0 AND var2 == 'foo'`
--- End diff --
It seems as if the below stellar always throws an exception. Is it by
design that `default` clauses are always evaluated? If so can you mention that
here?
```
foo := 500
match{ foo < 100 : THROW('oops'), foo > 200 : 'ok', default :
THROW('exception thrown') }
```
---
