syntax Coercion type
Documentation for syntax
Coercion type assembled from the following types:
To accept one type but coerce it automatically to another, use the accepted type as an argument to the target type. If the accepted type is
Any it can be omitted.
sub f(Int(Str) , Str() )f '10', 10;# OUTPUT: «Int Str␤»sub foo(Date(Str) ) ;foo "2016-12-01";# OUTPUT: «Date␤2016-12-01␤»
The coercion is performed by calling the method with the name of the type to coerce to, if it exists. In this example, we're calling the builtin method
Date on the
Str class. The method is assumed to return the correct type—no additional checks on the result are currently performed.
Coercion can also be performed on return types:
sub square-str (Int --> Str(Int))for 2,4, *² … 256 -># OUTPUT: «2² is 1 figures long␤# 4² is 2 figures long␤# 16² is 3 figures long␤# 256² is 5 figures long␤»
In this example, coercing the return type to
Str allows us to directly apply string methods, such as the number of characters.