Synopsis Assignment to a field of a tuple or datatype.
Syntax
Exp1 [ Name = Exp2 ]
Description
Field assignment applies to all values that have named components like tuples and relations with named elements, data types, and locations. Field assignment returns a new value in which the named component has been replaced by a new value.
Exp1 should evaluate to a tuple or datatype with a field Name; assign the value of Exp2 to that field
Field assignment applies to all values that have named components like tuples and relations with named elements, data types, and locations. Field assignment returns a new value in which the named component has been replaced by a new value.
Name stands for itself and is not evaluated.
Examples
rascal>tuple[int key, str val] T = <1, "abc">; tuple[int key,str val]: <1,"abc"> rascal>T[val = "def"]; tuple[int key,str val]: <1,"def"> rascal> T; tuple[int key,str val]: <1,"abc">Observe that field assignment creates a new value with an updated field. The old value remains unchanged as can be seen from the unchanged value of T in the above example.