'*********************************************
'*     Elementary operations on fractions    *
'* ----------------------------------------- *
'* This program allows user performing       *
'* operations on fractions such as:          *
'*         3/4 x 8/9 - 4/5                   *
'*                                           *
'* Sample run:                               *
'*                                           *
'* ? 3,4                                     *
'* ? *                                       *
'* ? 8,9                                     *
'* ? +                                       *
'* ? -4,5                                    *
'* ? =                                       *
'* Result is -2/15                           *
'* ----------------------------------------- *
'* Ref.: "Mathématiques par l'informatique   *
'*        individuelle (1) par H. Lehning    *
'*        et D. Jakubowicz, Masson, Paris,   *
'*        1982" [BIBLI 06].                  *
'*********************************************
cls
print
'*** enter first fraction p/q (p=0 to exit) ***
10 input p,q : if p=0 or q=0 then end
'*** enter operator:
'    = to view current result p/q
'    s to save current result
'    +,-,*,/ arithmetic operator
'***
20 input c$
if c$="=" then print "Result is ";p;"/";q:goto 20
if c$="s" then g=p:h=q:goto 10
'*** enter next fraction r/s (if s=0, take current stored result) ***
50 input r,s : if r=0 then end
if s=0 then r=g:s=h
'computing result
if c$="+" then gosub 310
if c$="-" then gosub 300
if c$="*" then gosub 360
if c$="/" then gosub 330
gosub 390
goto 20
300 r=-r
310 p=p*s+q*r
goto 370
330 b=r
r=s:s=b
360 p=p*r
370 q=q*s 'common denominator for all operations
return
390 t=p
'simplification section
u=q
400 b=t-u*int(t/u)
if b=0 then goto 450
t=u:u=b
goto 400
450 p=p/u:q=q/u
return

'end of file fraction.bas