diff options
| -rw-r--r-- | builtin.c | 1 | ||||
| -rw-r--r-- | compile.c | 35 | ||||
| -rw-r--r-- | compile.h | 1 | ||||
| -rw-r--r-- | docs/content/3.manual/manual.yml | 36 | ||||
| -rw-r--r-- | lexer.l | 1 | ||||
| -rw-r--r-- | parser.y | 6 | ||||
| -rw-r--r-- | tests/all.test | 8 |
7 files changed, 88 insertions, 0 deletions
@@ -963,6 +963,7 @@ static const char* const jq_builtins[] = { " def _while: " " if cond then ., (update | _while) else empty end; " " _while;", + "def limit(n; exp): if n < 0 then exp else foreach exp as $item ([n, null]; if .[0] < 1 then empty else [.[0] -1, $item] end; .[1]) end;", }; #undef LIBM_DD @@ -374,6 +374,41 @@ block gen_reduce(const char* varname, block source, block init, block body) { gen_op_bound(LOADVN, res_var)); } +block gen_foreach(const char* varname, block source, block init, block update, block extract) { + block output = gen_op_targetlater(JUMP); + block state_var = gen_op_var_fresh(STOREV, "foreach"); + block loop = BLOCK(gen_op_simple(DUP), + // get a value from the source expression: + source, + // bind the $varname to that value for all the code in + // this block_bind() to see: + block_bind(gen_op_unbound(STOREV, varname), + // load the loop state variable + BLOCK(gen_op_bound(LOADVN, state_var), + // generate updated state + update, + // save the updated state for value extraction + gen_op_simple(DUP), + // save new state + gen_op_bound(STOREV, state_var), + // extract an output... + extract, + // ...and output it + output), + OP_HAS_VARIABLE)); + block foreach = BLOCK(gen_op_simple(DUP), + init, + state_var, + gen_op_target(FORK, loop), + loop, + // At this point `foreach`'s input will be on + // top of the stack, and we don't want to output + // it, so we backtrack. + gen_op_simple(BACKTRACK)); + inst_set_target(output, foreach); + return foreach; +} + block gen_definedor(block a, block b) { // var found := false block found_var = gen_op_var_fresh(STOREV, "found"); @@ -32,6 +32,7 @@ block gen_subexp(block a); block gen_both(block a, block b); block gen_collect(block expr); block gen_reduce(const char* varname, block source, block init, block body); +block gen_foreach(const char* varname, block source, block init, block update, block extract); block gen_definedor(block a, block b); block gen_condbranch(block iftrue, block iffalse); block gen_and(block a, block b); diff --git a/docs/content/3.manual/manual.yml b/docs/content/3.manual/manual.yml index ac0e70e0..54e727b3 100644 --- a/docs/content/3.manual/manual.yml +++ b/docs/content/3.manual/manual.yml @@ -1777,6 +1777,42 @@ sections: input: '[10,2,5,3]' output: ['20'] + - title: `limit(n; exp)` + body: | + + The `limit` function extracts up to `n` outputs from `exp`. + + examples: + - program: '[limit(3;.[])]' + input: '[0,1,2,3,4,5,6,7,8,9]' + output: ['[0,1,2]'] + + - title: `foreach` + body: | + + The `foreach` syntax is similar to `reduce`, but intended to + allow the construction of `limit` and reducers that produce + intermediate results (see example). + + The form is `foreach EXP as $var (INIT; UPDATE; EXTRACT)`. + Like `reduce`, `INIT` is evaluated once to produce a state + value, then each output of `EXP` is bound to `$var`, `UPDATE` + is evaluated for each output of `EXP` with the current state + and with `$var` visible. Each value output by `UPDATE` + replaces the previous state. Finally, `EXTRACT` is evaluated + for each new state to extract an output of `foreach`. + + This is mostly useful only for constructing `reduce`- and + `limit`-like functions. + + examples: + - program: '[foreach .[] as $item + ([[],[]]; + if $item == null then [[],.[0]] else [(.[0] + [$item]),[]] end; + if $item == null then .[1] else empty end)]' + input: '[1,2,3,4,null,"a","b",null]' + output: ['[[1,2,3,4],["a","b"]]'] + - title: Recursion body: | @@ -51,6 +51,7 @@ struct lexer_param; "or" { return OR; } "end" { return END; } "reduce" { return REDUCE; } +"foreach" { return FOREACH; } "//" { return DEFINEDOR; } "try" { return TRY; } "catch" { return CATCH; } @@ -63,6 +63,7 @@ struct lexer_param; %token ELSE "else" %token ELSE_IF "elif" %token REDUCE "reduce" +%token FOREACH "foreach" %token END "end" %token AND "and" %token OR "or" @@ -234,6 +235,11 @@ Term "as" '$' IDENT '|' Exp { jv_free($5); } | +"foreach" Term "as" '$' IDENT '(' Exp ';' Exp ';' Exp ')' { + $$ = gen_foreach(jv_string_value($5), $2, $7, $9, $11); + jv_free($5); +} | + "if" Exp "then" Exp ElseBody { $$ = gen_cond($2, $4, $5); } | diff --git a/tests/all.test b/tests/all.test index 1fdb10a0..e68998b7 100644 --- a/tests/all.test +++ b/tests/all.test @@ -226,6 +226,14 @@ null 1 [1,2,4,8,16,32,64] +[foreach .[] as $item ([3, null]; if .[0] < 1 then empty else [.[0] -1, $item] end; .[1])] +[11,22,33,44,55,66,77,88,99] +[11,22,33] + +[limit(3; .[])] +[11,22,33,44,55,66,77,88,99] +[11,22,33] + # # Slices # |