gh-113: Add operator ISFUNC.

Author: python-processing-unit

docs/SPECIFICATION.html

@@ -705,7 +705,7 @@
 
 - `BOOL: EXIST(SYMBOL: name)` = MUST return `TRUE` if `name` resolves to a visible readable binding in the current lexical environment chain and `FALSE` otherwise.
 
-- `BOOL: ISBOOL/ISINT/ISFLT/ISSTR/ISTNS/ISMAP(ANY: value)` = MUST return `TRUE` if the runtime type of `value` is respectively `BOOL`, `INT`, `FLT`, `STR`, `TNS`, or `MAP`, and `FALSE` otherwise.
+- `BOOL: ISBOOL/ISINT/ISFLT/ISSTR/ISTNS/ISMAP/ISFUNC(ANY: value)` = MUST return `TRUE` if the runtime type of `value` is respectively `BOOL`, `INT`, `FLT`, `STR`, `TNS`, `MAP`, or `FUNC`, and `FALSE` otherwise.
 
 - `STR: TYPE(ANY: value)` = MUST return the runtime type name of `value` as a `STR`. For core language values, the result MUST be one of `BOOL`, `INT`, `FLT`, `STR`, `TNS`, `MAP`, `FUNC`, or `THR`. For null or otherwise unrecognized internal values, the result MUST be `NULL`. Extension-defined values MUST report their registered type names.
 

src/builtins.c

@@ -6545,6 +6545,11 @@ static Value builtin_ismap(Interpreter* interp, Value* args, int argc, Expr** ar
     return value_bool(args[0].type == VAL_MAP);
 }
 
+static Value builtin_isfunc(Interpreter* interp, Value* args, int argc, Expr** arg_nodes, Env* env, int line, int col) {
+    (void)arg_nodes; (void)env; (void)interp; (void)line; (void)col;
+    return value_bool(args[0].type == VAL_FUNC);
+}
+
 static Value builtin_type(Interpreter* interp, Value* args, int argc, Expr** arg_nodes, Env* env, int line, int col) {
     (void)arg_nodes; (void)env; (void)interp; (void)line; (void)col;
     return value_str(value_type_name(args[0]));
@@ -9073,6 +9078,7 @@ static BuiltinFunction builtins_table[] = {
     {"ISSTR", 1, 1, builtin_isstr},
     {"ISTNS", 1, 1, builtin_istns},
     {"ISMAP", 1, 1, builtin_ismap},
+    {"ISFUNC", 1, 1, builtin_isfunc},
     {"TYPE", 1, 1, builtin_type},
     {"SIGNATURE", 1, 1, builtin_signature},
 

tests/cases/failing/isfunc-arity-two.pre

@@ -0,0 +1 @@
+ISFUNC(TRUE, FALSE)

tests/cases/failing/isfunc-arity-zero.pre

@@ -0,0 +1 @@
+ISFUNC()

tests/cases/passing/isfunc.pre

@@ -0,0 +1,23 @@
+BOOL: sample_bool_true = TRUE
+BOOL: sample_bool_false = FALSE
+INT: sample_int = -0d7
+FLT: sample_flt = 0d3.5
+STR: sample_str = "prefix"
+TNS: sample_tns = [0d1, 0d2]
+MAP: sample_map = <"n" = 0d1>
+
+FUNC INT: sample_func(INT: value){
+    RETURN(value)
+}
+
+THR(sample_thr){}
+
+ASSERT(ISFUNC(sample_func))
+REFUTE(ISFUNC(sample_bool_true))
+REFUTE(ISFUNC(sample_bool_false))
+REFUTE(ISFUNC(sample_int))
+REFUTE(ISFUNC(sample_flt))
+REFUTE(ISFUNC(sample_str))
+REFUTE(ISFUNC(sample_tns))
+REFUTE(ISFUNC(sample_map))
+REFUTE(ISFUNC(sample_thr))