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doc/langdef: update documentation for .map() and .filter() (#338)
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These macros are documented as explicitly not applying to map values,
but it seems like this documentation is out-of-date.

Signed-off-by: Steve Kuznetsov <skuznets@redhat.com>
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stevekuznetsov authored Apr 11, 2024
1 parent c1e9c1a commit 7e81610
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31 changes: 20 additions & 11 deletions doc/langdef.md
Original file line number Diff line number Diff line change
Expand Up @@ -704,19 +704,28 @@ macros are:
if the predicate of exactly one element/key evaluates to `true`, and the
rest to `false`. Any other combination of boolean results evaluates to
`false`, and any predicate error causes the macro to raise an error.
* `e.map(x, t)`: transforms a list `e` by taking each element `x` to the
function given by the expression `t`, which can use the variable `x`. For
instance, `[1, 2, 3].map(n, n * n)` evaluates to `[1, 4, 9]`. Any evaluation
error for any element causes the macro to raise an error. The `map()` macro
is not supported when `e` is a map.
* `e.map(x, t)`:
* transforms a list `e` by taking each element `x` to the
function given by the expression `t`, which can use the variable `x`. For
instance, `[1, 2, 3].map(n, n * n)` evaluates to `[1, 4, 9]`. Any evaluation
error for any element causes the macro to raise an error.
* transforms a map `e` by taking each key in the map `x` to the function
given by the expression `t`, which can use the variable `x`. For
instance, `{'one': 1, 'two': 2}.map(k, k)` evaluates to `['one', 'two']`.
Any evaluation error for any element causes the macro to raise an error.
* `e.map(x, p, t)`: Same as the two-arg map but with a conditional `p` filter
before the value is transformed.
* `e.filter(x, p)`: returns the sublist of all elements `x` of list `e` which
evaluate to `true` in the predicate expression `p` (which can use variable
`x`). For instance, `[1, 2, 3].filter(i, i % 2 > 0)` evaluates to `[1, 3]`.
If no elements evaluate to `true`, the result is an empty list. Any
evaluation error for any element causes the macro to raise an error. The
`filter()` macro is not supported on maps.
* `e.filter(x, p)`:
* for a list `e`, returns the sublist of all elements `x` which
evaluate to `true` in the predicate expression `p` (which can use variable
`x`). For instance, `[1, 2, 3].filter(i, i % 2 > 0)` evaluates to `[1, 3]`.
If no elements evaluate to `true`, the result is an empty list. Any
evaluation error for any element causes the macro to raise an error.
* for a map `e`, returns the list of all map keys `x` which
evaluate to `true` in the predicate expression `p` (which can use variable
`x`). For instance, `{'one': 1, 'two': 2}.filter(k, k == 'one')` evaluates
to `['one']`. If no elements evaluate to `true`, the result is an empty
list. Any evaluation error for any element causes the macro to raise an error.

### Field Selection

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12 changes: 10 additions & 2 deletions tests/simple/testdata/macros.textproto
Original file line number Diff line number Diff line change
Expand Up @@ -203,7 +203,11 @@ section {
errors: { message: "divide by zero" }
}
}
# The map() macro is currently not supported for maps.
test {
name: "map_extract_keys"
expr: "{'John': 'smart', 'Paul': 'cute', 'George': 'quiet', 'Ringo': 'funny'}.map(key, key) == ['John', 'Paul', 'George', 'Ringo']"
value: { bool_value: true }
}
}
section {
name: "filter"
Expand Down Expand Up @@ -257,7 +261,11 @@ section {
errors: { message: "divide by zero" }
}
}
# The filter() macro is currently not supported for maps.
test {
name: "map_filter_keys"
expr: "{'John': 'smart', 'Paul': 'cute', 'George': 'quiet', 'Ringo': 'funny'}.filter(key, key == 'Ringo') == ['Ringo']"
value: { bool_value: true }
}
}
section {
name: "nested"
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