Long multiplication: Difference between revisions
Long multiplication in BASIC-256
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700 IF E THEN V = VAL ( MID$ (D$,E,1)) + C:C = V > 9:V = V - 10 * C:E$ = STR$ (V) + E$:E = E - 1: GOTO 700
720 RETURN</syntaxhighlight>
=={{header|BASIC256}}==
{{trans|Liberty BASIC}}
<syntaxhighlight lang="freebasic">print "2^64"
a$ = "1"
for i = 1 to 64
a$ = multByD$(a$, 2)
next
print a$
print "(check with native BASIC-256)"
print 2^64
print "(looks OK)"
#now let's do b$*a$ stuff
print
print "2^64*2^64"
print longMult$(a$, a$)
print "(check with native BASIC-256)"
print 2^64*2^64
print "(looks OK)"
end
function max(a, b)
if a > b then
return a
else
return b
end if
end function
function longMult$(a$, b$)
signA = 1
if left(a$,1) = "-" then
a$ = mid(a$,2,1)
signA = -1
end if
signB = 1
if left(b$,1) = "-" then
b$ = mid(b$,2,1)
signB = -1
end if
c$ = ""
t$ = ""
shift$ = ""
for i = length(a$) to 1 step -1
d = fromradix((mid(a$,i,1)),10)
t$ = multByD$(b$, d)
c$ = addLong$(c$, t$+shift$)
shift$ += "0"
next
if signA * signB < 0 then c$ = "-" + c$
return c$
end function
function multByD$(a$, d)
#multiply a$ by digit d
c$ = ""
carry = 0
for i = length(a$) to 1 step -1
a = fromradix((mid(a$,i,1)),10)
c = a * d + carry
carry = int(c/10)
c = c mod 10
c$ = string(c) + c$
next
if carry > 0 then c$ = string(carry) + c$
return c$
end function
function addLong$(a$, b$)
#add a$ + b$, for now only positive
l = max(length(a$), length(b$))
a$ = pad$(a$,l)
b$ = pad$(b$,l)
c$ = "" #result
carry = 0
for i = l to 1 step -1
a = fromradix((mid(a$,i,1)),10)
b = fromradix((mid(b$,i,1)),10)
c = a + b + carry
carry = int(c/10)
c = c mod 10
c$ = string(c) + c$
next
if carry > 0 then c$ = string(carry) + c$
return c$
end function
function pad$(a$,n) #pad$ from right with 0 to length n
pad$ = a$
while length(pad$) < n
pad$ = "0" + pad$
end while
end function
</syntaxhighlight>
{{out}}
<pre>2^64
18446744073709551616
(check with native BASIC-256)
1.84467440737e+19
(looks OK)
2^64*2^64
340282366920938463463374607431768211456
(check with native BASIC-256)
3.40282366921e+38
(looks OK)</pre>
=={{header|Batch File}}==
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