Difference between revisions of "CSC231 Recursive Multiplication"
(Created page with '--~~~~ ---- =Definition= * a and b are integers * a is a positive integer and can be null * algorithm ** mult( a, b ) returns a multiplied by b ** if a==0 mult( a, b ) = 0 **…') |
(→Assembly Version) |
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;;; --------------------------------------------------------------------------- | ;;; --------------------------------------------------------------------------- | ||
asm_main: | asm_main: | ||
| − | + | mov eax, [ a ] ; print a | |
| − | mov eax, [ a ] | ||
call print_int | call print_int | ||
call print_nl | call print_nl | ||
| − | mov eax, [ b ] | + | mov eax, [ b ] ; print b |
call print_int | call print_int | ||
call print_nl | call print_nl | ||
| − | push dword[ a ] | + | push eax ; make room for return value |
| − | push dword[ b ] | + | push dword[ a ] ; pass a |
| − | call mult | + | push dword[ b ] ; pass b |
| − | pop eax | + | call mult ; compute mult( a, b ) |
| + | pop eax ; get result | ||
call print_int | call print_int | ||
call print_nl | call print_nl | ||
Revision as of 10:14, 29 November 2010
--D. Thiebaut 15:10, 29 November 2010 (UTC)
Definition
- a and b are integers
- a is a positive integer and can be null
- algorithm
- mult( a, b ) returns a multiplied by b
- if a==0 mult( a, b ) = 0
- if a==1 mult( a, b ) = b
- otherwise mult( a, b ) = mult( a-1, b ) + b
Python Version
#! /usr/bin/python
# mult.py
# implements multiplication as a recursive
# process. Works only with integers. a must
# be positive.
# mult( a, b ) = 0 if a == 0
# mult( a, b ) = b if a == 1
# = b + mult( a-1, b ) otherwise
#
def mult( a, b ):
if a==0: return 0
if a==1: return b
return b + mult( a-1, b )
def main():
a = 0
b = 100
print "a = %d b = %d mult( %d, %d ) = %d " \
% ( a, b, a, b, mult( a, b ) )
a = 1
b = 100
print "a = %d b = %d mult( %d, %d ) = %d " \
% ( a, b, a, b, mult( a, b ) )
a = 3
b = 100
print "a = %d b = %d mult( %d, %d ) = %d " \
% ( a, b, a, b, mult( a, b ) )
a = 100
b = 0
print "a = %d b = %d mult( %d, %d ) = %d " \
% ( a, b, a, b, mult( a, b ) )
main()
Assembly Version
