# Big Integers

## version 1 by Jeremy John Reeder

Version 1 of Big Integers by Jeremy John Reeder begins here.
[Allows addition and multiplication of texts which represent integers. This is a work-around for the 32-bit limitation of Inform's native arithmetic operations.]
[To be implemented in the future:
* Subtraction
* Division
* Negative integers]
To decide which number is the numeric equivalent of (T - some text):
if there is a text of T in the Table of Number Parsing:
decide on the number corresponding to a text of T in the Table of Number Parsing;
decide on zero.
[TODO: parse multi-digit numbers]
Table 1 - Number Parsing
 Text Number "0" 0 "1" 1 "2" 2 "3" 3 "4" 4 "5" 5 "6" 6 "7" 7 "8" 8 "9" 9
To decide which text is (A - some text) plus (B - some text):
let the carried digit be zero;
while A is not "" or B is not "" or the carried digit is not zero:
let the ones digit of A be the numeric equivalent of the last character in A;
let the ones digit of B be the numeric equivalent of the last character in B;
let the sum of the ones digits be (ones digit of A) plus (ones digit of B) plus (carried digit);
now the answer is "[remainder after dividing the sum of the ones digits by ten][answer]";
now the carried digit is (sum of the ones digits) divided by ten;
now A is the first (number of characters in A minus one) characters in A;
now B is the first (number of characters in B minus one) characters in B;
To decide which text is (A - some text) plus (B - a number):
decide on A plus "[B]".
To decide which text is (A - a number) plus (B - some text):
decide on "[A]" plus B.
To decide which text is (A - some text) times (B - some text):
let the carried digit be zero;
while A is not "" or B is not "" or the carried digit is not zero:
let the ones digit of A be the numeric equivalent of the last character in A;
let the ones digit of B be the numeric equivalent of the last character in B;
let the product of the ones digits be (ones digit of A) times (ones digit of B) plus (carried digit);
now the answer is "[remainder after dividing the product of the ones digits by ten][answer]";
now the carried digit is (product of the ones digits) divided by ten;
now A is the first (number of characters in A minus one) characters in A;
now B is the first (number of characters in B minus one) characters in B;
To decide which text is (A - some text) times (B - a number):
decide on A times "[B]".
To decide which text is (A - a number) times (B - some text):
decide on "[A]" times B.
To decide which text is the first (N - a number) characters in (T - some text):
let R be "";
repeat with X running from 1 to N:
now R is "[R][character number (X) in T]";
decide on R.
To decide which text is the last character in (T - some text):
let N be the number of characters in T;
decide on character number (N) in T.
To decide which number is the greater of (A - a number) and (B - a number):
if A is greater than B:
decide on A;
otherwise:
decide on B.
To decide which text is the greater of (A - some text) and (B - some text):
if the number of characters in A is greater than the number of characters in B:
decide on A;
if the number of characters in B is greater than the number of characters in A:
decide on B;
otherwise:
let the two numbers be a list of texts;
add A to the two numbers;
add B to the two numbers;
sort the two numbers;
decide on entry two in the two numbers.
Big Integers ends here.