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Similar to ES5, ucode's language grammar allows comma separated list expressions
in various contexts. Unless such lists happen to be part of a function call
or array construction expression, only the last result of such an expression
list should be used while still evaluating all sub-expressions, triggering
side effects such as function calls or variable assignments.
-- Expect stdout --
4
[ 1, 3 ]
{ "a": true, "b": 1 }
function call
[ "test", "assigment" ]
true
true
true
[ 2, 3 ]
-- End --
-- Testcase --
{%
// only the last value is considered
print(1 + (2, 3), "\n");
// in array constructors, parenthesized lists are reduced to the last value
print([ (0, 1), (2, 3) ], "\n");
// in object constructors, parenthesized lists are reduced to the last value
print({ a: (false, true), b: (0, 1) }, "\n");
// all list expressions are evaluated and may have side effects, even if
// results are discareded
x = (print("function call\n"), y = "assigment", "test");
print([x, y], "\n");
// property access operates on the last value of a parenthesized list expression
print(({foo: false}, {foo: true}).foo, "\n");
print(({foo: false}, {foo: true})["foo"], "\n");
// computed property access uses the last list expression value
print(({foo: true})["bar", "baz", "foo"], "\n");
// same list semantics apply to function call parameters
((...args) => print(args, "\n"))((1, 2), 3);
%}
-- End --
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