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Let's first allow more complex expressions such as 1 or 1+2 or 1+2+3+4 This starts with a single number, then can add a plus sign and a number (possibly more than once):
| Code Block | ||
|---|---|---|
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add: NUMBER (PLUS NUMBER)* | {code
The
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*
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symbol
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means
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"zero
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or
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more
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times".
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If
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you
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want
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to
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implement
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both
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addition
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and
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subtraction,
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you
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can
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make
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a
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small
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adjustment:
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| Code Block | ||
|---|---|---|
| ||
add: NUMBER ((PLUS | MINUS) NUMBER)* MINUS : '-'; |
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