arktype•2mo 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•2mo ago

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

JesusTheHunOP•2mo ago

Or something

?? 😂

Dimava•2mo ago

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

JesusTheHunOP•2mo ago

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

TizzySaurus•2mo 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•2mo ago

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

TizzySaurus•2mo 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`

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