Test if a con­tainer holds an entry with the given key.

In­ter­face

(c: Con­tainer, k: Key) => Void.

Laws

• The value must ac­tu­ally be de­leted, not set to un­defined if pos­sible. Ar­rays be­come sparse if a value in their midst is de­leted.

Spe­cial­iz­a­tion Notes

No im­ple­ment­a­tion provided for String since String is read only. No im­ple­ment­a­tion for Ar­ray since has() dis­reg­ards sparse slots in ar­rays (so a de­lete op would be the same as as­sign(myAr­ray, idx, un­defined)) which would be in­con­sist­ent.