92 lines
2.0 KiB
Plaintext
92 lines
2.0 KiB
Plaintext
# Milestone 5: conditional optional unwrapping, guards, and multi-unwrap.
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observe func(counter @mut i32, value ?i32) ?i32 {
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counter^ = counter^ + 1
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return value
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}
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main func() i32 {
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total i32 := 0
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# present optional scalar -> binds v to the unwrapped value
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a ?i32 := 40
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if a |v| {
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total = total + v # 40
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} else {
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total = total + 99
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}
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# null -> else branch taken; the binding is not in scope there
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b ?i32 := null
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if b |v| {
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total = total + v
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} else {
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total = total + 2 # 42
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}
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# optional pointer present -> binds q to a non-null @i32; deref proves it
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n i32 := 0
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p ?@i32 := &n
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if p |q| {
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total = total + q^ # +0
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}
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# optional pointer null -> skipped
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z ?@i32 := null
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if z |_| {
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total = total + 1000
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}
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# guarded multi-unwrap exposes every capture to the guard and then-block
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age ?i32 := 2
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if a and age |value, years : value + years == 42| {
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total = total
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} else {
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total = total + 100
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}
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# parenthesized chains and three-value unwraps are equivalent
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bonus ?i32 := 0
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if (a and age and bonus) |value, years, extra : value + years + extra == 42| {
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total = total
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} else {
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total = total + 100
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}
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# false guards use the else branch, or simply fall through without one
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if a |value : value == 0| {
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total = total + 100
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} else {
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total = total
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}
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if a |value : value == 0| {
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total = total + 100
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}
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# a failed unwrap prevents later expressions from being evaluated
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calls i32 := 0
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if b and observe(&calls, age) |missing, observed| {
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total = total + missing + observed
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}
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if calls != 0 {
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total = total + 100
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}
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# short-circuiting also applies after an earlier successful unwrap
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if a and b and observe(&calls, age) |value, missing, observed| {
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total = total + value + missing + observed
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}
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if calls != 0 {
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total = total + 100
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}
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# optional pointers participate in multi-unwrap and guards
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if a and p |value, q : value == 40 and q^ == 0| {
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total = total
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} else {
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total = total + 100
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}
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return total # expect exit code 42
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}
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