diff options
| -rw-r--r-- | eval.c | 13 | ||||
| -rw-r--r-- | tests/010/qquote.tl | 30 | ||||
| -rw-r--r-- | txr.1 | 30 |
3 files changed, 73 insertions, 0 deletions
@@ -3661,6 +3661,7 @@ static val expand_qquote_rec(val qquoted_form, val qq, val unq, val spl) return cons(quote_s, cons(qquoted_form, nil)); } else { val sym = car(qquoted_form); + val args, uqform; if (sym == spl) { val error_msg = if3(spl == sys_splice_s, @@ -3691,6 +3692,18 @@ static val expand_qquote_rec(val qquoted_form, val qq, val unq, val spl) val opts = expand_qquote(second(qquoted_form), qq, unq, spl); val keys = expand_qquote(rest(rest(qquoted_form)), qq, unq, spl); return rlcp(list(tree_construct_s, opts, keys, nao), qquoted_form); + } else if (sym == expr_s && consp((args = cdr(qquoted_form))) + && !cdr(args) && consp((uqform = car(args))) && + car(uqform) == unq && consp(cdr(uqform)) && !cddr(uqform)) + { + val gs = gensym(nil); + val ret = list(let_s, cons(list(gs, cadr(uqform), nao), nil), + list(if_s, list(atom_s, gs, nao), + list(list_s, list(quote_s, var_s, nao), + gs, nao), + list(list_s, list(quote_s, expr_s, nao), + gs, nao), nao), nao); + return rlcp_tree(ret, qquoted_form); } else { val f = sym; val r = cdr(qquoted_form); diff --git a/tests/010/qquote.tl b/tests/010/qquote.tl new file mode 100644 index 00000000..e6daad3a --- /dev/null +++ b/tests/010/qquote.tl @@ -0,0 +1,30 @@ +(let ((nullsym nil) + (sym 's) + (atom "abc") + (cons '(x y z)) + (dwim '[])) + (tree-bind (x y (op arg)) ^(a b @,nullsym) + (assert (eq op 'sys:var)) + (assert (eq arg nullsym))) + (tree-bind (x y (op arg)) ^(a b @,sym) + (assert (eq op 'sys:var)) + (assert (eq arg sym))) + (tree-bind (x y (op arg)) ^(a b @,atom) + (assert (eq op 'sys:var)) + (assert (eq arg atom))) + (tree-bind (x y (op arg)) ^(a b @,cons) + (assert (eq op 'sys:expr)) + (assert (eq arg cons))) + (tree-bind (x y (op arg)) ^(a b @,dwim) + (assert (eq op 'sys:expr)) + (assert (eq arg dwim))) + (tree-bind (x y (op arg . tail)) ^(a b (sys:expr ,sym . foo)) + (assert (eq op 'sys:expr)) + (assert (eq arg sym)) + (assert (eq tail 'foo))) + (tree-bind (x y (op arg0 arg1)) ^(a b (sys:expr ,sym foo)) + (assert (eq op 'sys:expr)) + (assert (eq arg0 sym)) + (assert (eq arg1 'foo))) + (tree-bind (x y (op)) ^(a b (sys:expr)) + (assert (eq op 'sys:expr)))) @@ -12175,6 +12175,36 @@ The expression is evaluated to produce the list .codn "(6 8)" , and this list is spliced into the quoted template. + +.meIP >> @,* expr +This syntax is not a distinct quasiquoting operator, but rather the combination of +an unquote occurring as a meta-expression, denoting the structure +.codn "(sys:expr ,expr)" . +This structure is treated specially by the quasiquote expander. Code is generated +for it such that if +.meta expr +evaluates to an value +.meta val +which is an +.codn atom , +then the result will be the +.mono +.meti (sys:var << val ) +.onom +structure. If +.meta val +is a +.code cons +rather than an +.codn atom , +then the result is the +.mono +.meti (sys:expr << val ) +.onom +structure. In other words, when quasiquoting is used to insert a value under the +.code @ +meta prefix, the expander generates code to analyze the type of the value, and +produce to the form which is most likely intended. .RE .TP* "Dialect Notes:" |