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miyaokamarina/conditions.js

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Revisions

  1. miyaokamarina revised this gist Nov 24, 2018. 1 changed file with 2 additions and 0 deletions.
    2 changes: 2 additions & 0 deletions conditions.js
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    Original file line number Diff line number Diff line change
    @@ -1,3 +1,5 @@
    // Licensed under CC BY 4.0.

    type $If<X: boolean, Then, Else = empty> = $Call<
    & ((true, Then, Else) => Then)
    & ((false, Then, Else) => Else),
  2. miyaokamarina renamed this gist Apr 19, 2018. 1 changed file with 0 additions and 0 deletions.
    0 typelevel-logic.js → conditions.js
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    File renamed without changes.
  3. miyaokamarina created this gist Apr 19, 2018.
    67 changes: 67 additions & 0 deletions typelevel-logic.js
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    Original file line number Diff line number Diff line change
    @@ -0,0 +1,67 @@
    type $If<X: boolean, Then, Else = empty> = $Call<
    & ((true, Then, Else) => Then)
    & ((false, Then, Else) => Else),
    X,
    Then,
    Else,
    >;

    type $Not<X: boolean> = $If<X, false, true>;
    type $And<X: boolean, Y: boolean> = $If<X, Y, false>;
    type $Or<X: boolean, Y: boolean> = $If<X, true, Y>;

    type $Gte<X, Y> = $Call<
    & ($Subtype<X> => true)
    & (mixed => false),
    Y,
    >;

    ////

    declare var a: $Gte<number, string>;

    /* error 1 */ (a: true);
    /* ok */ (a: false);

    declare var b: $Gte<number, number>;

    /* ok */ (b: true);
    /* error 2 */ (b: false);

    declare var c: $If<true, 1, 2>;

    /* ok */ (c: 1);
    /* error 3 */ (c: 2);

    declare var d: $If<false, 1, 2>;

    /* error 4 */ (d: 1);
    /* ok */ (d: 2);

    ////

    declare var e: $If<$Gte<number, string>, 1, 2>;

    /* error 5 */ (e: 1);
    /* ok */ (e: 2);

    declare var f: $If<$Gte<number, number>, 1, 2>;

    /* ok */ (f: 1);
    /* error 6 */ (f: 2);

    ////

    type IsNumber<X> = $Gte<number, X>;

    type NumberTo12<X> = $If<IsNumber<X>, 1, 2>;

    declare var g: NumberTo12<string>;

    /* error 7 */ (g: 1);
    /* ok */ (g: 2);

    declare var h: NumberTo12<number>;

    /* ok */ (h: 1);
    /* error 8 */ (h: 2);