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Code Issues 1 Releases Wiki Activity

Add break special.

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The break special form can break out of both loops
and functions with an early (nil) return. Mainly useful
for generated code in macros, and should probably be discouraged
in user written code.
This commit is contained in:
Calvin Rose
2019-03-09 16:47:05 -05:00
parent a363dce943
commit 4a111b38b1
4 changed files with 57 additions and 8 deletions
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45
src/core/specials.c
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@@ -471,6 +471,41 @@ static int32_t janetc_addfuncdef(JanetCompiler *c, JanetFuncDef *def) {
return janet_v_count(scope->defs) - 1;
}
/*
* break
*
* jump :end or retn if in function
*/
static JanetSlot janetc_break(JanetFopts opts, int32_t argn, const Janet *argv) {
JanetCompiler *c = opts.compiler;
JanetScope *scope = c->scope;
(void) argv;
if (argn != 0) {
janetc_cerror(c, "expected no arguments");
return janetc_cslot(janet_wrap_nil());
}
while (scope) {
if (scope->flags & (JANET_SCOPE_FUNCTION | JANET_SCOPE_WHILE))
break;
scope = scope->parent;
}
if (NULL == scope) {
janetc_cerror(c, "break must occur in while loop or closure");
return janetc_cslot(janet_wrap_nil());
}
if (scope->flags | JANET_SCOPE_FUNCTION) {
/* Just return, either in IIFE or closure body */
janetc_emit(c, JOP_RETURN_NIL);
JanetSlot s = janetc_cslot(janet_wrap_nil());
s.flags |= JANET_SLOT_RETURNED;
return s;
} else {
/* Tag the instruction so the while special can turn it into a proper jump */
janetc_emit(c, 0x80 | JOP_JUMP);
return janetc_cslot(janet_wrap_nil());
}
}
/*
* :whiletop
* ...
@@ -495,7 +530,7 @@ static JanetSlot janetc_while(JanetFopts opts, int32_t argn, const Janet *argv)
labelwt = janet_v_count(c->buffer);
janetc_scope(&tempscope, c, 0, "while");
janetc_scope(&tempscope, c, JANET_SCOPE_WHILE, "while");
/* Compile condition */
cond = janetc_value(subopts, argv[0]);
@@ -569,6 +604,13 @@ static JanetSlot janetc_while(JanetFopts opts, int32_t argn, const Janet *argv)
if (!infinite) c->buffer[labelc] |= (uint32_t)(labeld - labelc) << 16;
c->buffer[labeljt] |= (uint32_t)(labelwt - labeljt) << 8;
/* Calculate breaks */
for (int32_t i = labelwt; i < labeld; i++) {
if (c->buffer[i] == (0x80 | JOP_JUMP)) {
c->buffer[i] = JOP_JUMP | ((labeld - i) << 8);
}
}
/* Pop scope and return nil slot */
janetc_popscope(c);
@@ -686,6 +728,7 @@ error2:
/* Keep in lexicographic order */
static const JanetSpecial janetc_specials[] = {
{"break", janetc_break},
{"def", janetc_def},
{"do", janetc_do},
{"fn", janetc_fn},