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Short-circuiting Boolean "and" and "or" operators.

This commit is contained in:
Stephen Dolan
2012-09-04 20:38:59 +01:00
parent c5ab3b2336
commit 6e6ea50763
5 changed files with 62 additions and 5 deletions

View File

@ -348,14 +348,49 @@ block gen_definedor(block a, block b) {
return c;
}
static block gen_condbranch(block iftrue, block iffalse) {
block b = gen_noop();
block_append(&iftrue, gen_op_target(JUMP, iffalse));
block_append(&b, gen_op_target(JUMP_F, iftrue));
block_append(&b, iftrue);
block_append(&b, iffalse);
return b;
}
block gen_and(block a, block b) {
// a and b = if a then (if b then true else false) else false
block code = gen_op_simple(DUP);
block_append(&code, a);
block if_a_true = gen_op_simple(POP);
block_append(&if_a_true, b);
block_append(&if_a_true, gen_condbranch(gen_op_const(LOADK, jv_true()),
gen_op_const(LOADK, jv_false())));
block_append(&code, gen_condbranch(if_a_true,
block_join(gen_op_simple(POP), gen_op_const(LOADK, jv_false()))));
return code;
}
block gen_or(block a, block b) {
// a or b = if a then true else (if b then true else false)
block code = gen_op_simple(DUP);
block_append(&code, a);
block if_a_false = gen_op_simple(POP);
block_append(&if_a_false, b);
block_append(&if_a_false, gen_condbranch(gen_op_const(LOADK, jv_true()),
gen_op_const(LOADK, jv_false())));
block_append(&code, gen_condbranch(block_join(gen_op_simple(POP), gen_op_const(LOADK, jv_true())),
if_a_false));
return code;
}
block gen_cond(block cond, block iftrue, block iffalse) {
block b = gen_op_simple(DUP);
block_append(&b, cond);
block_append(&iftrue, gen_op_target(JUMP, iffalse));
block_append(&b, gen_op_target(JUMP_F, iftrue));
block_append(&b, block_join(gen_op_simple(POP), iftrue));
block_append(&b, block_join(gen_op_simple(POP), iffalse));
block_append(&b, gen_condbranch(block_join(gen_op_simple(POP), iftrue),
block_join(gen_op_simple(POP), iffalse)));
return b;
}

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@ -27,6 +27,8 @@ block gen_both(block a, block b);
block gen_collect(block expr);
block gen_assign(block expr);
block gen_definedor(block a, block b);
block gen_and(block a, block b);
block gen_or(block a, block b);
block gen_cond(block cond, block iftrue, block iffalse);

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@ -17,6 +17,8 @@
"then" { return THEN; }
"else" { return ELSE; }
"elif" { return ELSE_IF; }
"and" { return AND; }
"or" { return OR; }
"end" { return END; }
"//" { return DEFINEDOR; }
"."|"="|";"|"["|"]"|","|":"|"("|")"|"{"|"}"|"|"|"+"|"\$" { return yytext[0];}

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@ -34,9 +34,13 @@
%token ELSE "else"
%token ELSE_IF "elif"
%token END "end"
%token AND "and"
%token OR "or"
%right "//"
%nonassoc '=' SETPIPE
%nonassoc EQ
%left OR
%left AND
%left '+'
@ -99,6 +103,14 @@ Exp '=' Exp {
$$ = gen_assign(assign);
} |
Exp "or" Exp {
$$ = gen_or($1, $3);
} |
Exp "and" Exp {
$$ = gen_and($1, $3);
} |
Exp "//" Exp {
$$ = gen_definedor($1, $3);
} |

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@ -254,3 +254,9 @@ def inc(x): x |= .+1; inc(.[].a)
[{"foo":[1,2], "bar": 42}, {"foo":[1], "bar": null}, {"foo":[null,false,3], "bar": 18}, {"foo":[], "bar":42}, {"foo": [null,false,null], "bar": 41}]
[[1,2], [1], [3], [42], [41]]
.[] | [.[0] and .[1], .[0] or .[1]]
[[true,[]], [false,1], [42,null], [null,false]]
[true,true]
[false,true]
[false,true]
[false,false]