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Code Issues 1 Releases Wiki Activity

POC "rest" pattern in destructuring

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Add support for using [& rest] to match the remaining values
in an array or tuple when destructuring.

the rest pattern is implemented by pushing remaining values in the
rhs to the stack once & is found on the lhs.
Then tuple is called and the result is assigned
to the next symbol on the lhs.

This commit DOES NOT implement handling for malformed patterns.
This commit is contained in:
Ian Shehadeh 2022-01-15 14:51:44 -05:00
parent f2f421a0a2
commit cb5af974a4
2 changed files with 54 additions and 0 deletions
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39
src/core/specials.c
View File

@ -154,6 +154,45 @@ static int destructure(JanetCompiler *c,
for (int32_t i = 0; i < len; i++) {
JanetSlot nextright = janetc_farslot(c);
Janet subval = values[i];
if (!janet_cstrcmp(janet_unwrap_symbol(subval), "&")) {
JanetSlot argi = janetc_farslot(c);
JanetSlot arg = janetc_farslot(c);
JanetSlot len = janetc_farslot(c);
janetc_emit_si(c, JOP_LOAD_INTEGER, argi, i, 0);
janetc_emit_ss(c, JOP_LENGTH, len, right, 0);
// loop condition
// reuse arg slot for the condition result
int32_t label_loop_start = janetc_emit_sss(c, JOP_EQUALS, arg, argi, len, 0);
int32_t label_loop_cond_jump = janetc_emit_si(c, JOP_JUMP_IF, arg, 0, 0);
// loop body
janetc_emit_sss(c, JOP_GET, arg, right, argi, 0);
janetc_emit_s(c, JOP_PUSH, arg, 0);
janetc_emit_ssi(c, JOP_ADD_IMMEDIATE, argi, argi, 1, 0);
// loop
// jump back to the start of the loop
int32_t label_loop_loop = janet_v_count(c->buffer);
janetc_emit(c, JOP_JUMP);
int32_t label_loop_exit = janet_v_count(c->buffer);
c->buffer[label_loop_cond_jump] |= (label_loop_exit - label_loop_cond_jump) << 16;
c->buffer[label_loop_loop] |= (label_loop_start - label_loop_loop) << 8;
janetc_freeslot(c, argi);
janetc_freeslot(c, arg);
janetc_freeslot(c, len);
janetc_emit_s(c, JOP_MAKE_TUPLE, nextright, 1);
leaf(c, janet_unwrap_symbol(values[i + 1]), nextright, attr);
janetc_freeslot(c, nextright);
break;
}
if (i < 0x100) {
janetc_emit_ssu(c, JOP_GET_INDEX, nextright, right, (uint8_t) i, 1);
} else {

15
test/suite0001.janet
View File

@ -137,6 +137,21 @@
(assert (= a 1) "dictionary destructuring 3")
(assert (= b 2) "dictionary destructuring 4")
(assert (= c 4) "dictionary destructuring 5 - expression as key"))
(let [test-tuple [:a :b 1 2]]
(def [a b one two] test-tuple)
(assert (= a :a) "tuple destructuring 1")
(assert (= b :b) "tuple destructuring 2")
(assert (= two 2) "tuple destructuring 3"))
(let [test-tuple [:a :b 1 2]]
(def [a & rest] test-tuple)
(assert (= a :a) "tuple destructuring 4 - rest")
(assert (= rest [:b 1 2]) "tuple destructuring 5 - rest"))
(do
(def [a b & rest] [:a :b nil :d])
(assert (= a :a) "tuple destructuring 6 - rest")
(assert (= b :b) "tuple destructuring 7 - rest")
(pp rest)
(assert (= rest [nil :d]) "tuple destructuring 8 - rest"))
# Marshal