Longest string challenge: Difference between revisions

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=={{header|RPL}}==

This program complies with the list of restrictions:

The main hack is based on the fact that the <code>SUB</code> function, which extracts one or more characters from a string, returns the null character if its arguments exceed the size of the string. ~~A minor hack is to use <code>INCR</code> and <code>DECR</code> commands, instead of forbidden arithmetic operations.~~

The main hack is based on the fact that the <code>SUB</code> function, which extracts one or more characters from a string, returns the null character if its arguments exceed the size of the string.

A second hack is to use a string to count the number of compliant strings already in the stack: the <code>+</code> and <code>STO+</code> commands present in the code are not arithmetic operations, but string operations aiming at appending characters.

The user stack is both the standard input and output.

≪ 1 → count

≪ "X" → count

≪ 1 CF <span style="color:grey">@ flag 1 set means there are at least 2 strings in the stack</span>

'''WHILE''' "String?" "" INPUT DUP SIZE '''REPEAT'''

'''IF''' 1 FS? '''THEN'''

'''CASE'''

DUP2 SWAP SIZE DUP SUB NUM NOT '''THEN''' ~~DROP '''END'''~~

DUP2 SWAP SIZE DUP SUB NUM NOT '''THEN'''

~~DUP2~~ ~~SIZE~~ ~~DUP~~ ~~SUB NUM NOT '''THEN''' 'count' INCR ROLLD 'count' DECR DROPN 1 'count' STO~~ '''END'''

DROP '''END'''

'~~count~~' ~~INCR DROP~~

DUP2 SIZE DUP SUB NUM NOT '''THEN'''

count "X" + SIZE ROLLD count SIZE DROPN "X" 'count' STO '''END'''

"X" 'count' STO+

'''END'''

'''ELSE''' 1 SF '''END'''