# ListToMap(A, B)¶

ListToMap allows mappings to be described by a pair of lists of equal lengths. The image of an element x, which appears in position n in the first list, is then the nth element of the second list. A default value or default function can be specified to be used when x does not appear in the first list. In the absence of defaults, an error will occur in that case.

match: (List A, List B) -> A -> B
match(la, lb) creates a map with no default source or target values defined by lists la and lb of equal length. The target of a source value x in la is the value y with the same index lb. Error: if la and lb are not of equal length. Note: when this map is applied, an error occurs when applied to a value missing from la.
match: (List A, List B, A -> B) -> A -> B
match(la, lb, f) creates a map defined by lists la and lb of equal length. The target of a source value x in la is the value y with the same index lb. Argument f is used as the function to call when the given function argument is not in la. The value returned is f applied to that argument.
match: (List A, List B, A) -> B
match(la, lb, a) creates a map defined by lists la and lb of equal length, where a is used as the default source value if the given one is not in la. The target of a source value x in la is the value y with the same index lb. Error: if la and lb are not of equal length.
match: (List A, List B, A, A -> B) -> B
match(la, lb, a, f) creates a map defined by lists la and lb of equal length. and applies this map to a. The target of a source value x in la is the value y with the same index lb. Argument f is a default function to call if a is not in la. The value returned is then obtained by applying f to argument a.
match: (List A, List B, A, B) -> B
match(la, lb, a, b) creates a map defined by lists la and lb of equal length. and applies this map to a. The target of a source value x in la is the value y with the same index lb. Argument b is the default target value if a is not in la. Error: if la and lb are not of equal length.
match: (List A, List B, B) -> A -> B
match(la, lb, b) creates a map defined by lists la and lb of equal length, where b is used as the default target value if the given function argument is not in la. The target of a source value x in la is the value y with the same index lb. Error: if la and lb are not of equal length.