1*4882a593SmuzhiyunCopyright (c) 1986 by University of Toronto. Written by Henry Spencer. Not derived from licensed software. 2*4882a593Smuzhiyun 3*4882a593SmuzhiyunPermission is granted to anyone to use this software for any purpose on any computer system, and to redistribute it freely, subject to the following restrictions: 4*4882a593Smuzhiyun 5*4882a593Smuzhiyun1. The author is not responsible for the consequences of use of this software, no matter how awful, even if they arise from defects in it. 6*4882a593Smuzhiyun 7*4882a593Smuzhiyun2. The origin of this software must not be misrepresented, either by explicit claim or by omission. 8*4882a593Smuzhiyun 9*4882a593Smuzhiyun3. Altered versions must be plainly marked as such, and must not be misrepresented as being the original software. 10*4882a593Smuzhiyun 11*4882a593SmuzhiyunBeware that some of this code is subtly aware of the way operator precedence is structured in regular expressions. Serious changes in regular-expression syntax might require a total rethink. 12