arktype•5d ago

`narrow` vs `satisfying`

I've ran across both functions, I can see the signatures are the same, but the type are not. I was wondering what the different is, between the two ?

7 Replies

Dimava•5d ago

One is for input another is for output Or something So it's different for morphs only

JesusTheHunOP•5d ago

Or something

?? 😂

Dimava•5d ago

Well I didn't use it myself so can't say for sure

JesusTheHunOP•5d ago

kk, I'll try to compare the two with in/out

TizzySaurus•5d ago

    narrow(predicate: Predicate): BaseRoot {
        return this.constrainOut("predicate", predicate)
    }

    satisfying(predicate: Predicate): BaseRoot {
        return this.constrain("predicate", predicate)
    }

    narrow(predicate: Predicate): BaseRoot {
        return this.constrainOut("predicate", predicate)
    }

    satisfying(predicate: Predicate): BaseRoot {
        return this.constrain("predicate", predicate)
    }

this is the difference in the source code narrow applies the constraint to the output, whereas satisfying applies the constraint to the input

JesusTheHunOP•5d ago

so to see an actual difference, I would need to pipe the type in order to alter its input, correct ?

TizzySaurus•5d ago

There'd need to be some form of transform, yes. Not necessarily a .pipe() explicitly though. E.g.:

type("string.numeric.parse").narrow(x => {...}) // `x` is a number
type("string.numeric.parse").satisfying(x => {...}) // `x` is a string

type("string.numeric.parse").narrow(x => {...}) // `x` is a number
type("string.numeric.parse").satisfying(x => {...}) // `x` is a string

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`narrow` vs `satisfying`