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# coding=utf-8
name = 'expr/3'
slug = 'arithmetic expressions with meaning'
description = '''\
<p>Write a DCG with the starting symbol <code>expr</code> for the language of arithmetic expressions consisting of numbers (without leading zeros), addition and multiplication. Subexpressions can be grouped using parentheses. The meaning of a word in this language is the numeric value of the represented arithmetic expression.</p>
<p>Example words: <code>(1+2)*3</code>, <code>42*8*3</code>, <code>(2+1)*(3+4)</code>.</p>
<pre>
?- expr(N, ['(',2,'+',1,')','*','(',3,'+',4,')'], []). % (2+1)*(3+4) = 21
N = 21.
</pre>
'''
hint = {}
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