Palindromic Number in M4

Welcome to the Palindromic Number in M4 page! Here, you'll find the source code for this program as well as a description of how the program works.

Current Solution

divert(-1)
define(`show_usage',
`Usage: please input a non-negative integer
m4exit(`1')')

dnl is_valid(n)
define(`is_valid', `eval(regexp(`$1', `^\s*-?[0-9]+\s*$') >= 0)')

dnl is_palindrome(str)
define(`is_palindrome', `_is_palindrome(`$1', 0, decr(len(`$1')))')

dnl _is_palidrome(str, left, right)
dnl while left < right:
dnl   if str[left] != str[right]:
dnl     Return 0
dnl   left = left + 1
dnl   right = right - 1
dnl Return 1
define(`_is_palindrome',
`ifelse(
    eval($2 >= $3), 1, `1',
    substr(`$1', $2, 1), substr(`$1', $3, 1), `_is_palindrome(`$1', incr($2), decr($3))', `0'dnl
)'dnl
)
divert(0)dnl
ifelse(eval(ARGC < 1 || len(ARGV1) < 1 || !is_valid(ARGV1)), 1, `show_usage()')dnl
ifelse(eval(ARGV1 < 0), 1, `show_usage()',)dnl
ifelse(is_palindrome(ARGV1), 1, `true', `false')

Palindromic Number in M4 was written by:

• rzuckerm

If you see anything you'd like to change or update, please consider contributing.

How to Implement the Solution

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How to Run the Solution

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