The BigInt->new function takes decimal, hex, and binary in the usual Perl literal number syntax. But it doesn't take Octal—it treats a leading zero as nothing special and parses a decimal number.

Even the documentation for autocreating Big constants doesn't mention octal, so presumably those are left as normal scalars. But trying it, I find that 

perl -MMath::BigInt=:constant -e"print 077"

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and 
perl -e"print 077"

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produce different results! So that leads to a silent change in the program, which is not good.

The affect of autocreate-constant might be considered a bug at least in the docs, but that's not why I'm writing.

I'm pondering how to parse octal values, changing a program that just reads text from the user and converts to a number using $val = oct($val) if $val =~ /^0/;. Writing $val= new BigInt:: ($val); will handle decimal, binary, hex, but not octal.

My first idea is to detect the leading zero first and convert the octal string into a binary string using only string-based operations, one character at a time. Anybody got a better way?

—John

In reply to BigInt and octal input by John M. Dlugosz

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