Repetition

Since we can use the result of an addition in another addition, we can theoretically add any amount of numbers together. This is not a very nice way of dealing with the problem.

> add 1 add 2 add 3 add 4 5
15

Instead we can use Repeat which evaluates to an array of of its inner type.

  Func("sum")
    .arg(new Repeat(value))
    .setExec((args: number[]) => args.reduce((sum, next) => sum + next, 0)),

> sum 1 2 3 4 5
15
> sum
0
> sum 1 2 3 mul 4 5
26
> mul 2 sum 3 4 5
24
> mul sum 3 4 5 2
Error: Parser finished but expected type <t.value>.

Notice how the last example didn't work. This is because Repeat parses until the end of input is reached, meaning the 2 is consumed by sum and not given as an argument to mul. This can also be seen in the grammar. We fix this in the next chapter.

l.calc:
 | <t.value> EOI

t.value:
 | "add"      <t.value>   <t.value>
 | "mul"      <t.value>   <t.value>
 | "sum"      <r.t.value>
 | "pi"      
 | <p.number>

r.t.value:
 | <t.value> * EOI