$extendedSyntax: what changed

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Title: $extendedSyntax

New		Line
1	+	The [[global compiler directives\|global compiler directive]]
2	+
3	+	``` pascal
4	+	{$extendedSyntax on}
5	+	```
6	+
7	+	turns on additional syntax. The [[FPC]] has this by default on. The short notation is
8	+
9	+	``` pascal
10	+	{$X+}
11	+	```
12	+
13	+	/
14	+
15	+	``` pascal
16	+	{$X‑}
17	+	```
18	+
19	+	.
20	+
21	+	## Affected syntax
22	+
23	+	- [[Function\|Functions]] can be called as if they were [[Procedure\|procedures]]. The function result is discarded. This is potentially harmful if, for example, the function allocated new memory space and returned a pointer to it. Nonetheless, managed data types are insusceptible to leakage. Implementing a [[management operators\|management operator]] can turn any
24	+	``` pascal
25	+	record
26	+	```
27	+
28	+	into a managed data type.
29	+	- Integer arithmetic expressions are allowed on [[Pointer\|pointers]]. The directive \[\[\$pointerMath\\|
30	+	``` pascal
31	+	{$pointerMath}
32	+	```
33	+
34	+	\]\] had to be on for that during the respective pointer type’s definition.
35	+	- Pointers become ordered and can be compared using \[\[Less than\\|
36	+	``` pascal
37	+	<
38	+	```
39	+
40	+	\]\],\[\[Greater than\\|
41	+
42	+	``` pascal
43	+	>
44	+	```
45	+
46	+	\]\],
47	+
48	+	``` pascal
49	+	<=
50	+	```
51	+
52	+	and
53	+
54	+	``` pascal
55	+	>=
56	+	```
57	+
58	+	. Typed pointers have to correspond to each other. The \[\[Equal\\|
59	+
60	+	``` pascal
61	+	=
62	+	```
63	+
64	+	\]\] and \[\[Not equal\\|
65	+
66	+	``` pascal
67	+	<>
68	+	```
69	+
70	+	\]\] comparisons work regardless of the
71	+
72	+	``` pascal
73	+	{$extendedSyntax}
74	+	```
75	+
76	+	state.
77	+
78	+	## Notes
79	+
80	+	- If you have
81	+	``` pascal
82	+	{$extendedSyntax off}
83	+	```
84	+
85	+	, you can still do pointer arithmetic with routines from other units if they have been compiled with
86	+
87	+	``` pascal
88	+	{$extendedSyntax on}
89	+	```
90	+
91	+	, for example \[\[Inc and Dec#Special behaviors\\|
92	+
93	+	``` pascal
94	+	inc
95	+	```
96	+
97	+	and
98	+
99	+	``` pascal
100	+	dec
101	+	```
102	+
103	+	\]\]:
104	+
105	+	{\$extendedSyntax off} var
106	+
107	+	` p: pChar;`
108	+
109	+	begin
110	+
111	+	` p := nil;`\
112	+	` inc(p, 42); { no problem }`
113	+
114	+	end.
115	+
116	+	</syntaxhighlight>
117	+
118	+	Similarly, unusual comparison operations may be accessible with foreign routines.
119	+
120	+	- Built-in functions can never be called as if they were procedures
121	+
122	+	{\$extendedSyntax on} begin
123	+
124	+	` pi; { discardFunctionResultDemo.pas(4,4) Error: Illegal expression }`
125	+
126	+	end.
127	+
128	+	</syntaxhighlight>
129	+
130	+	even though a custom \[<https://www.freepascal.org/docs-html/rtl/system/pi.html>
131	+
132	+	``` pascal
133	+	pi
134	+	```
135	+
136	+	``` pascal
137	+	function
138	+	```
139	+
140	+	\] doing exactly the same would be acceptable.
141	+
142	+	- Although with
143	+	``` pascal
144	+	{$extendedSyntax on}
145	+	```
146	+
147	+	pointers become ordered, they do not become ordinal data types; the standard functions \[\[Ord\\|
148	+
149	+	``` pascal
150	+	ord
151	+	```
152	+
153	+	\]\],
154	+
155	+	``` pascal
156	+	succ
157	+	```
158	+
159	+	and
160	+
161	+	``` pascal
162	+	pred
163	+	```
164	+
165	+	are still not applicable on pointers.
166	+
167	+	## Comparative remarks
168	+
169	+	- [[Standard Pascal]] does not define any of those “extensions”.
170	+
171	+	## See also
172	+
173	+	- [[Pascal for C users]]
174	+
175	+	---
176	+	From the Free Pascal wiki, page "$extendedSyntax", as it stood on 2022-10-23 after a change by Bart, out of the wiki's dump of 2024-05-26. Copyright stays with the author who wrote it, according to the old wiki's [[Licensing]] page. If you have concerns about this material, [message the admin](/wiki-contact).

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