Update syntax-list-comprehensions.md

rfcs/syntax-list-comprehensions.md

@@ -1,6 +1,6 @@
 ## Summary
 
-Introduce a form of list comprehension using `for var in iterator do` syntax.
+Introduce a form of list comprehension using `n for-in-do` syntax.
 
 ## Motivation
 
@@ -12,3 +12,38 @@ When traversing a table to exclude all the odd numbers you'd be creating a large
 ## Design
 
 To solve these problems, I propose a `n for-in-do` expression form that is syntactically similar to a for statement, but lacks terminating `end`.
+
+The `n for-in-do` expression must match ``<identifier> for <identifier> in <expr> do``
+
+## Drawbacks
+
+List comprehensions may be misused.
+
+The list comprehensions have similar drawbacks to the if expression drawbacks
+https://github.com/Roblox/luau/blob/master/rfcs/syntax-if-expression.md
+
+## Alternatives
+
+### C#
+```csharp
+var list2 = from number in Enumerable.Range(0, 10) select 2*number;
+```
+
+### Rust (using cute)
+```rust
+let vector = c![x, for x in 1..10, if x % 2 == 0];
+```
+
+### Haskell
+```haskell
+[x * 2 | x <- [0 .. 99], x * x > 3]
+```
+
+### R
+```r
+ x <- 0:100
+ S <- 2 * x[x ^ 2 > 3]
+ ```
+
+### Function syntax
+List comprehensions could be implemented as functions like ``table.map`` or ``table.filter``