1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
|
<html><head>
<title>Evaluation</title>
<style type="text/css">
.example {
color: #000000;
background-color: #F5F5F5;
padding: 8px;
border: #808080;
border-style: solid;
border-width: 1px;
width:auto;
}
.button {
color: #000000;
background-color: #F5F5F5;
padding-top: 1px;
padding-bottom: 1px;
padding-left: 4px;
padding-right: 8px;
border: #808080;
border-style: solid;
border-width: 1px;
}
.box {
color: #000000;
padding-top: 4px;
padding-bottom: 4px;
padding-left: 16px;
padding-right: 16px;
border: #808080;
border-style: solid;
border-width: 1px;
}
</style>
</head>
<body>
<a href="../start.htm">Nyquist / XLISP 2.0</a> -
<a href="../manual/contents.htm">Contents</a> |
<a href="../tutorials/tutorials.htm">Tutorials</a> |
<a href="examples.htm">Examples</a> |
<a href="../reference/reference-index.htm">Reference</a>
<hr>
<h1>Evaluation</h1>
<hr>
<ol>
<li><nobr><a href="#with-errset">with-errset</a> - evaluate expressions without entering the <nobr><a href="../manual/xlisp.htm#break-loop">Break Loop</a></nobr></nobr></li>
<li><nobr><a href="#apply-star.htm">apply*</a> and <a href="#funcall-star.htm">funcall*</a> - work also with macros and special forms</nobr></li>
</ol>
<a name="with-errset"></a>
<hr>
<h2>with-errset</h2>
<hr>
<p>Evaluate an expression without entering the
<nobr><a href="../manual/xlisp.htm#break-loop">Break Loop</a></nobr>
on <a href="../reference/error.htm">error</a>
<nobr>or <a href="../reference/cerror.htm">cerror</a></nobr>:</p>
<pre class="example">
(defmacro <font color="#0000CC">with-errset</font> (expr &optional (print-flag nil))
`(progv '(<font color="#AA5500">*breakenable*</font>) '(nil)
(errset ,expr ,print-flag)))
</pre>
<p>See <a href="../reference/defmacro.htm">defmacro</a>,
<a href="../reference/errset.htm">errset</a>,
<a href="../reference/nil.htm">nil</a>,
<a href="../reference/lambda-keyword-optional.htm.htm">&optional</a>,
<a href="../reference/progv.htm">progv</a>.</p>
<p><b>Note:</b> <a href="../reference/errset.htm">errset</a> does not
protect against the <a href="../reference/break.htm">break</a> function.</p>
<p><nobr> <a href="#top">Back to top</a></nobr></p>
<a name="apply-star"></a><a name="funcall-star"></a>
<hr>
<h2>apply* and funcall*</h2>
<hr>
<p>In Lisp, macros and <nobr>special forms</nobr> are no functions. This
means that <a href="../reference/apply.htm">apply</a> and
<a href="../reference/funcall.htm">funcall</a> only work with functions of
type SUBR <nobr>[built-in</nobr> function] or CLOSURE [functions defined by
<a href="defun.htm">defun</a>, <a href="flet.htm">flet</a>,
<a href="labels.htm">labels</a>, or <a href="lambda.htm">lambda</a>], but
with macros and <nobr>special forms</nobr> a '<nobr>bad function</nobr>'
error is signalled. Here are two examples how to work around this
behaviour:</p>
<pre class="example">
(defun <font color="#0000CC">apply*</font> (function args)
(eval (cons function args)))
(defun <font color="#0000CC">funcall*</font> (function args)
(eval (cons function args)))
</pre>
<p><b>Warning:</b> These functions can produce unwanted
<nobr>side-effects</nobr> because macros and <nobr>special forms</nobr> do
not need to conform to functional evaluation rules. Use them on your own
risk.</p>
<p><nobr> <a href="#top">Back to top</a></nobr></p>
<hr>
<a href="../start.htm">Nyquist / XLISP 2.0</a> -
<a href="../manual/contents.htm">Contents</a> |
<a href="../tutorials/tutorials.htm">Tutorials</a> |
<a href="examples.htm">Examples</a> |
<a href="../reference/reference-index.htm">Reference</a>
</body></html>
|
