Question: Is implicit multiplication possible with Expression? about expression HOT 5 OPEN

@graycampbell it's not really possible at the moment I'm afraid. Two consecutive values are treated as an error unless one of them is registered as an operator. It might be possible to fudge it, e.g. by overriding pi with a postfix operator that multiplies the previous value by pi, but I'm not sure if that would work for all of your use cases.

from expression.

I also would like to have this. I've got the constants defined for Euler's number & PI:

        constants: [
            "π": Double.pi,
            "ℇ": Darwin.M_E,
        ],

and would like to have support for 3π.

For Android I use the following library and they support it: https://github.com/ezylang/EvalEx

from expression.

@vanniktech for that particular use-case, you can define them as postfix operators.

EDIT: I tested and can confirm that this works:

let expression = "2π"

let result = try Expression(
    expression,
    constants: ["π": .pi],
    symbols: [.postfix("π"): { $0[0] * .pi }]
).evaluate()

print(result) // 6.28319

from expression.

@graycampbell apologies, it seems I misled you! implicit multiplication is possible, at least for some cases. In addition to the solution for implicit multiplication of constants mentioned above (by using a postfix operator), you can also use the "()" operator to implement implicit multiplication of values in parenthesis, like this:

let expression = "4(5)"

let result = try Expression(
    expression,
    symbols: [
        .infix("()"): { $0[0] * $0[1] }
    ]
).evaluate()

print(result) // 20

from expression.

This is amazing! Can be closed from my side.

from expression.