Add unconditional begin statement to SSTNPL, and a basic test rom for…

… it.

roms/stnp_flowcon5/auto_flowcon5.stnp

@@ -0,0 +1,23 @@
+#unconditional begin block test.
+
+#only really useful with conditional `top` statements, and code formatting.
+
+#unconditional `begin` statements, and their `end` statements only use 
+#	'zerosize', so no additional memory is used.
+
+#IMPORTANT: do note, that when `end` statements are paired with looped blocks,
+#	a `goto` is used to facilitate the loop, so the above blurb depends
+#	on context!!
+
+var kb=0
+
+begin
+	prline press A to ask again, any other key to exit.
+	keyprompt
+	set kb
+	if kb,:A top
+	if kb,:a top
+
+end
+
+stop

textdocs/SSTNPL/command_overview.txt

@@ -213,9 +213,28 @@ Command documentation:
 				has been met, loop exits as normal.
 			- in conditional blocks, run conditional block from its start again
 				unconditionally.
+			- in non-looped blocks, do the same as with conditional blocks.
 	end   : used in conjunction with conditional code blocks 
 			(made via the conditional operation 'begin') 
 
+--begin blocks:
+
+	Begin blocks are mostly identical to conditional blocks, and are provided to allow use
+	of 'top' outside of conditional blocks and loops, or within specific scopes, 
+	which can be more readable than using gotos in some cases.
+
+	--Example (from roms/stnp_flowcon5):
+
+		var kb=0
+		begin
+			prline press A to ask again, any other key to exit.
+			keyprompt
+			set kb
+			if kb,:A top
+			if kb,:a top
+
+		end
+		stop
 
 --for loops:
 		NOTE: like conditional 'begin' statements, an 'end' statement is REQUIRED.
@@ -279,7 +298,7 @@ Command documentation:
 		top   : 
 			- in looped blocks, run next loop iteration, or if loop end condition 
 				has been met, loop exits as normal.
-			- in conditional blocks, run conditional block from its start again
+			- in conditional blocks/non-looped blocks, run conditional block from its start again
 				(bypasses conditional check that begun the block.)
 		goto : ordinary goto.
 		gsub : store next block (line) of code as return address. (same as normal gsub command)

vmsystem/stnplib.py

@@ -143,6 +143,22 @@ def p3(self, args, keyword, lineno, nvars, valid_nvars, labels, tables, destobj)
 		return
 
 
+class in_fcon_begin:
+	def __init__(self):
+		self.keywords=["begin"]
+	def p0(self, args, keyword, lineno):
+		return 0, None
+	def p1(self, args, keyword, lineno):
+		return []
+	def p2(self, args, keyword, lineno, nvars, valid_nvars, labels, tables):
+		fsyntax_begin(lineno, keyword)
+
+		return 0, None
+	def p3(self, args, keyword, lineno, nvars, valid_nvars, labels, tables, destobj):
+		blockname=fcon_begin(loop=False)
+		destobj.write('''#unconditional begin
+zerosize;;''' + fcon_loopback() + "\n")
+		return
 class in_fcon_end:
 	def __init__(self):
 		self.keywords=["end"]
@@ -2373,6 +2389,7 @@ def __init__(self, srcobj, destpath, sourcepath, bpname):
 		in_fcon_break(),
 		in_fcon_end(),
 		in_fcon_loop(),
+		in_fcon_begin(),
 		in_fcon_top(),
 		in_for(),
 		in_condgoto(["if"], "gotoif", condmode=0),#conditionals