Allow numbers in a cryptarithm

[arnaud-m]

At this time, a sequence of digits is always parsed as a word.

The grammar must be extended so that a sequence of numbers can also be parsed as a number.

• Use ticks as optional delimiter for words.
• A word must be enclosed by ticks if its first letter is a digit.
• A sequence of digits not enclosed by ticks is a number.

Here are a few examples of new cryptarithms.

10 * A = BC
10 * A10 = 'ABCD'
10 * "10A" = "ABCD"
10 * '10A' = 'ABCD'

[arnaud-m]

In fact, the third example including a word with fixed digit makes no sense. Let us consider the classical SEND+MORE=MONEY.

• 9END+108E=10NEY : how do we store that M=1, O=0 ... ?
• 9END+M08E=10NEY is wrong because M is already assigned 1.

In fact, the information must be given as a pair (cryptarithm, partial solution).

So, the grammar must be extended as follows.

• A word is never enclosed by ticks.
• A sequence of digits enclosed by single ticks is a number.

[arnaud-m]

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