Add notion of local definitons in ZF

backend/Builtin/Syntax.icl

@@ -474,7 +474,7 @@ bs_layout_rule =
 bs_let =
 	{ syntax_title         = "let expression"
 	, syntax_patterns      = map exact ["let", "in", "let in"]
-	, syntax_code          = ["let ... in ..."]
+	, syntax_code          = ["let ... [in ...]"]
 	, syntax_description   = "An expression that introduces new scope."
 	, syntax_doc_locations = [CLR 5 "3.5.1" "_Toc311798003"]
 	, syntax_examples      =
@@ -487,6 +487,8 @@ bs_let =
 		  add_bootstrap "expression = undef" $
 		  EXs "macrorhs"
 		  "let // Multi-line let expressions\n\tfunction args = body\n\tselector = expr\n\t// ...\nin expression"
+		, EXs "macro"
+		  "[z\\x<-[0..]\n,let (y,z) = fun x\n] //the let MUST end with a newline"
 		]
 	}
 bs_let_before =
@@ -849,12 +851,12 @@ bs_with =
 
 bs_zf =
 	{ syntax_title         = "list comprehension"
-	, syntax_patterns      = map exact ["ZF-expression", "ZF", "zf", "*comprehension", "<-", "<\\|-", "<-:", "\\\\\\\\", ",", "&", "\\|"]
+	, syntax_patterns      = map exact ["ZF-expression", "ZF", "zf", "*comprehension", "<-", "<\\|-", "<-:", "\\\\\\\\", ",", "&", "\\|", "let"]
 	, syntax_code          =
 		[ "[... \\\\ ... <- ...]"
 		, "{... \\\\ ... <- ...}"
 		]
-	, syntax_description   = "Constructs a list or array composed of elements drawn from other lists or arrays."
+	, syntax_description   = "Constructs a list or array composed of elements drawn from other lists or arrays. It is possible to use local definitions as well (see {{`let`}})."
 	, syntax_doc_locations = [CLR 6 "4.2.1" "_Toc311798024", CLR 6 "4.4.1" "_Toc311798032"]
 	, syntax_examples      = map (add_imports ["StdEnv", "StdMaybe"] o EXs "macro")
 		[ "cartesian    = [(x,y) \\\\ x <- [1,2,3], y <- [10,20]] // Cartesian product: (1,10), (1,20), (2,10), (2,20), (3,10), (3,20)"