Condition Funcs Guide

Condition Funcs in R

cond

Returns a function, fn, which encapsulates if/else, if/else, logic. It takes a list of functions, alternated by predicate and transformer. All of the arguments to fn are applied to each of the predicates in turn until one returns a "truthy" value, at which point fn returns the result of applying its arguments to the corresponding transformer.

Func testF = (Func)R.cond.runN(new List{
    R.lt.apply(0), R.always.run(1),
    R.gt.apply(0), R.always.run(-1),
    R.equals.apply(0), R.always.run(0)
});
testF.run(3); // 1
doWhen
Tests the final argument by passing it to the given predicate function. If the predicate is satisfied, the function will return the result of calling the whenTrueFn function with the same argument. If the predicate is not satisfied, the argument is returned as a wrapping list.
Func testF = (Func)R.doWhen.run(
    R.lt.apply(0),
    R.always.run(1)
);
testF.run(3); // 1
ifElse
Creates a function that will process either the onTrue or the onFalse function depending upon the result of the condition predicate.
Func testF = (Func)R.ifElse.run(
    R.lt.apply(0),
    R.always.run(1),
    R.always.run(0)
);
testF.run(3); // 1
unless
Tests the final argument by passing it to the given predicate function. If the predicate is not satisfied, the function will return the result of calling the whenFalseFn function with the same argument. If the predicate is satisfied, the argument is returned as a wrapping list.
Func testF = (Func)R.unless.run(
    R.lt.apply(0),
    R.always.run(0)
);
testF.run(-3); // 0
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