# TITLE:  Linear Congruence Solver 
# AUTHOR: Roy F.A. Maclean
# EMAIL:  rfamgm at gmail
# WEB:    http://www.spiderpixel.co.uk/caspro 
# DATE:   28Nov1997, 6Jun1999, 18Jan2000, 3Jul2007
# MAKE:   CASIO
# MODEL:  9850
# SIZE:   207+90    
#         
# NOTES:  
# Solves linear congruences of the form ax=b(mod m) for x.
# Enter the values a,b,m and the solns will be displayed.
#
# Two program areas needed
#
# Prog "EUCSUB" inputs are X,Y.Outputs are X,A,C.
# Where new X=GCD(old X,Y)=A(old X)+CY.



@@ Program "LCONG"

Lbl 0
"AX=B MOD M"
"A"?->U:"B"?->V:"M"?->M
U->X:M->Y
Prog "E"
If X=1
Then AV-M*Int (AV/M)->G           
G<0=>M+G->G
G_
IfEnd
X=1=>Goto 0
Frac (V/X)=0=>Goto 1  
"NO SOLN"  
Goto 0
Lbl 1
U/X->I:V/X->J:M/X->K
X->H:I->X:K->Y
Prog "EUCSUB"
AJ-K*Int (AJ/K)->G                 
G<0=>G+K->G
For 0->C To H-1
G+CK_
Next
Goto 0


@@ Program "EUCSUB"

1->A~B:0->C~D
Lbl 1
Int (X/Y)         
X-AnsY->R
A-AnsD->E
C-AnsB->F
D->A:B->C:E->D
F->B:Y->X:R->Y
Y<>0=>Goto 1