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
|
\DOC set_fail
\TYPE {set_fail : (string -> (* -> **) -> * -> **)}
\SYNOPSIS
Specifies the failure string for a function evaluation.
\DESCRIBE
When applied to a string {s} and a function {f}, the function {set_fail}
gives a function which behaves identically to {f} except that on failure, the
failure string is {s}, regardless of what failure string {f} itself gives rise
to.
\FAILURE
Never fails.
\EXAMPLE
The following example shows how a failure string can be customized either by
using {set_fail} or by adding a toplevel error trap.
{
#BETA_CONV "1 + 1";;
evaluation failed BETA_CONV
#(set_fail `Term is not a beta-redex` BETA_CONV) "1 + 1";;
evaluation failed Term is not a beta-redex
#(BETA_CONV "1 + 1") ? failwith `Term is not a beta-redex`;;
evaluation failed Term is not a beta-redex
}
\SEEALSO
set_fail_prefix.
\ENDDOC
|
