Easier to read lambdas

[Jeff Dyer]

I have to admit that this is a quite unintuitive transformation for me. How
would bodies of multiple lambda arguments be expressed? If as a comma
separated list, then you have the list within a list problem again.

Anyway, separating the head of a lambda from the body is hard for me to
read. But perhaps that is because I'm just not used to it.

Jd


On 5/29/07 7:18 AM, Igor Bukanov wrote:

> Hi!
> 
> Consider the following es3 examples involving simple and more complex lamdas:
> 
> array.sort(function(a, b) { return a - b; });
> 
> array.sort(function(a, b) {
>     if (typeof a != "number" || typeof b != "number")
>         throw "Unexpected type of array element";
>     return a - b;
> });
> 
> setTimeout(function() {
>    if (someCondition)
>        reportTimeout();
> }, 1000);
> 
> This not only looks ugly due to that }); but IMO hard to read since it
> is not immediately obvious where the lambda parameter ends especially
> in the third example.
> 
> In es4 the first one can be written using function shortcut as:
> 
> array.sort(function(a, b) a - b);
> 
> But such shorter form is not available for multi-statement lambdas so
> the second and third examples will continue to look ugly and be hard
> to read (again IMO).
> 
> To mitigate this I suggest to allow to move the definition of the body
> of lambda used inside an expression statement to the end of the
> statement. This would make possible to write:
> 
> array.sort(function(a, b)) a - b;
> 
> array.sort(function(a, b)) {
>     if (typeof a != "number" || typeof b != "number")
>         throw "Unexpected type of array element";
>     return a - b;
> }
> 
> setTimeout(function(), 1000) {
>    if (someCondition)
>        reportTimeout();
> }
> 
> Here is more examples:
> 
> Upper-case the array:
> 
> var upper = array.map(function(elem)) elem.toUpperCase();
> 
> Do complex SQL transaction:
> 
> function doSomethingWithNewPeople() {
>    let selectSQL ="SELECT code, name from people where status='new'";
>    let insertSQL = "INSERT INTO young(name,age) values (?,?)";
>    connection.transaction(function(tx)) {
>        connection.prepare(function(selectStatement), selectSQL) {
>            connection.prepare(function(insertStatement), insertSQL) {
>                selectStatement.executeQuery(function(name, age)) {
>                    if (name.match(/.*Joe/) && age % 2)
>                        insertStatement.execute(name, age);
>                }
>            }
>        }
>    }
> }
> 
> In fact such notation competes with using generators for enumeratons. Compare:
> 
> for (let [index, elem] in array)
>     print("["+index+"]="+elem);
> 
> with
> 
> array.forEach(function(elem, index))
>     print("["+index+"]="+elem);
> 
> So how does it look for you?
> 
> Regards, Igor
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