Add named arguments with the &named symbol.

Similar to &keys, but more ergonomic.

CHANGELOG.md

@@ -2,6 +2,9 @@
 All notable changes to this project will be documented in this file.
 
 ## Unreleased - ???
+- Allow using `&named` in function prototypes for named arguments. This is a more ergonomic
+  variant of `&keys` that isn't as redundant, more self documenting, and allows extension to
+  things like default arguments.
 - Add `debugger` - an easy to use debugger function that just takes a fiber.
 - `dofile` will now start a debugger on errors if the environment it is passed has `:debug` set.
 - Add `debugger-on-status` function, which can be passed to `run-context` to start a debugger on

src/core/asm.c

@@ -553,6 +553,10 @@ static JanetAssembleResult janet_asm1(JanetAssembler *parent, Janet source, int
     x = janet_get1(s, janet_ckeywordv("vararg"));
     if (janet_truthy(x)) def->flags |= JANET_FUNCDEF_FLAG_VARARG;
 
+    /* Check structarg */
+    x = janet_get1(s, janet_ckeywordv("structarg"));
+    if (janet_truthy(x)) def->flags |= JANET_FUNCDEF_FLAG_STRUCTARG;
+
     /* Check source */
     x = janet_get1(s, janet_ckeywordv("source"));
     if (janet_checktype(x, JANET_STRING)) def->source = janet_unwrap_string(x);
@@ -884,6 +888,10 @@ static Janet janet_disasm_vararg(JanetFuncDef *def) {
     return janet_wrap_boolean(def->flags & JANET_FUNCDEF_FLAG_VARARG);
 }
 
+static Janet janet_disasm_structarg(JanetFuncDef *def) {
+    return janet_wrap_boolean(def->flags & JANET_FUNCDEF_FLAG_STRUCTARG);
+}
+
 static Janet janet_disasm_constants(JanetFuncDef *def) {
     JanetArray *constants = janet_array(def->constants_length);
     for (int32_t i = 0; i < def->constants_length; i++) {
@@ -933,6 +941,7 @@ Janet janet_disasm(JanetFuncDef *def) {
     janet_table_put(ret, janet_ckeywordv("bytecode"), janet_disasm_bytecode(def));
     janet_table_put(ret, janet_ckeywordv("source"), janet_disasm_source(def));
     janet_table_put(ret, janet_ckeywordv("vararg"), janet_disasm_vararg(def));
+    janet_table_put(ret, janet_ckeywordv("structarg"), janet_disasm_structarg(def));
     janet_table_put(ret, janet_ckeywordv("name"), janet_disasm_name(def));
     janet_table_put(ret, janet_ckeywordv("slotcount"), janet_disasm_slotcount(def));
     janet_table_put(ret, janet_ckeywordv("constants"), janet_disasm_constants(def));
@@ -986,6 +995,7 @@ JANET_CORE_FN(cfun_disasm,
         if (!janet_cstrcmp(kw, "source")) return janet_disasm_source(f->def);
         if (!janet_cstrcmp(kw, "name")) return janet_disasm_name(f->def);
         if (!janet_cstrcmp(kw, "vararg")) return janet_disasm_vararg(f->def);
+        if (!janet_cstrcmp(kw, "structarg")) return janet_disasm_structarg(f->def);
         if (!janet_cstrcmp(kw, "slotcount")) return janet_disasm_slotcount(f->def);
         if (!janet_cstrcmp(kw, "constants")) return janet_disasm_constants(f->def);
         if (!janet_cstrcmp(kw, "sourcemap")) return janet_disasm_sourcemap(f->def);

src/core/specials.c

@@ -822,6 +822,7 @@ static JanetSlot janetc_fn(JanetFopts opts, int32_t argn, const Janet *argv) {
     int selfref = 0;
     int seenamp = 0;
     int seenopt = 0;
+    int namedargs = 0;
 
     /* Begin function */
     c->scope->flags |= JANET_SCOPE_CLOSURE;
@@ -846,6 +847,9 @@ static JanetSlot janetc_fn(JanetFopts opts, int32_t argn, const Janet *argv) {
 
     /* Keep track of destructured parameters */
     JanetSlot *destructed_params = NULL;
+    JanetSlot *named_params = NULL;
+    JanetTable *named_table = NULL;
+    JanetSlot named_slot;
 
     /* Compile function parameters */
     params = janet_unwrap_tuple(argv[parami]);
@@ -853,9 +857,19 @@ static JanetSlot janetc_fn(JanetFopts opts, int32_t argn, const Janet *argv) {
     arity = paramcount;
     for (i = 0; i < paramcount; i++) {
         Janet param = params[i];
-        if (janet_checktype(param, JANET_SYMBOL)) {
+        if (namedargs) {
+            if (!janet_checktype(param, JANET_SYMBOL)) {
+                errmsg = "only named arguments can follow &named";
+                goto error;
+            }
+            Janet key = janet_wrap_keyword(janet_unwrap_symbol(param));
+            janet_table_put(named_table, key, param);
+            janet_v_push(named_params, janetc_farslot(c));
+        } else if (janet_checktype(param, JANET_SYMBOL)) {
             /* Check for varargs and unfixed arity */
-            if (!janet_cstrcmp(janet_unwrap_symbol(param), "&")) {
+            const uint8_t *sym = janet_unwrap_symbol(param);
+            if (sym[0] == '&') {
+                if (!janet_cstrcmp(sym, "&")) {
                     if (seenamp) {
                         errmsg = "& in unexpected location";
                         goto error;
@@ -870,7 +884,7 @@ static JanetSlot janetc_fn(JanetFopts opts, int32_t argn, const Janet *argv) {
                         goto error;
                     }
                     seenamp = 1;
-            } else if (!janet_cstrcmp(janet_unwrap_symbol(param), "&opt")) {
+                } else if (!janet_cstrcmp(sym, "&opt")) {
                     if (seenopt) {
                         errmsg = "only one &opt allowed";
                         goto error;
@@ -881,7 +895,7 @@ static JanetSlot janetc_fn(JanetFopts opts, int32_t argn, const Janet *argv) {
                     min_arity = i;
                     arity--;
                     seenopt = 1;
-            } else if (!janet_cstrcmp(janet_unwrap_symbol(param), "&keys")) {
+                } else if (!janet_cstrcmp(sym, "&keys")) {
                     if (seenamp) {
                         errmsg = "&keys in unexpected location";
                         goto error;
@@ -894,8 +908,23 @@ static JanetSlot janetc_fn(JanetFopts opts, int32_t argn, const Janet *argv) {
                         goto error;
                     }
                     seenamp = 1;
+                } else if (!janet_cstrcmp(sym, "&named")) {
+                    if (seenamp) {
+                        errmsg = "&named in unexpected location";
+                        goto error;
+                    }
+                    vararg = 1;
+                    structarg = 1;
+                    arity = i;
+                    seenamp = 1;
+                    namedargs = 1;
+                    named_table = janet_table(10);
+                    named_slot = janetc_farslot(c);
                 } else {
-                janetc_nameslot(c, janet_unwrap_symbol(param), janetc_farslot(c));
+                    janetc_nameslot(c, sym, janetc_farslot(c));
+                }
+            } else {
+                janetc_nameslot(c, sym, janetc_farslot(c));
             }
         } else {
             janet_v_push(destructed_params, janetc_farslot(c));
@@ -914,6 +943,14 @@ static JanetSlot janetc_fn(JanetFopts opts, int32_t argn, const Janet *argv) {
     }
     janet_v_free(destructed_params);
 
+    /* Compile named arguments */
+    if (namedargs) {
+        Janet param = janet_wrap_table(named_table);
+        destructure(c, param, named_slot, defleaf, NULL);
+        janetc_freeslot(c, named_slot);
+        janet_v_free(named_params);
+    }
+
     max_arity = (vararg || allow_extra) ? INT32_MAX : arity;
     if (!seenopt) min_arity = arity;
 

test/suite0011.janet

@@ -80,5 +80,12 @@
   "table rawget regression"
   (table/new -1))
 
+# Named arguments
+(defn named-arguments
+  [&named bob sally joe]
+  (+ bob sally joe))
+
+(assert (= 15 (named-arguments :bob 3 :sally 5 :joe 7)) "named arguments 1")
+
 (end-suite)