/*                                                   16 July 1999 */
GO_EROS():=block
(

print("ELEMENTARY ROW OPERATIONS",
       "Copyright 1999 by Laurence I. Gould, University of Hartford"),

print("[You may force program termination using the Interrupt button.]"),

print("CAUTIONS: Do not enter any symbol followed by a % except where asked.",
       "For example, x% is to be avoided."),
START%,
kill(EX%,NAME%,R%,C%,COR%,CORR%,X%,RI%,RF%,K%),
print("INSTRUCTIONS: ",
  "Enter either m% for multiplying a row by some constant,",
  "or i% for interchanging two rows,",
  "or ma% for multiplying a row by some constant and adding the result to
another row."),
CORR%: read("Have you already generated a matrix, plus its name, as input?",
  "(type y for Yes or n for No) "),
if CORR%=n then go(L_AA%),
NAME%: read("Enter the name you gave to the matrix: "),
R%: mat_nrows(NAME%),
C%: mat_ncols(NAME%),
if CORR%=y then go (L_AAA%),
L_AA%,
NAME%: read("Enter the name of the matrix (e.g., m): "),
R%: read("Enter the number of rows: "),
C%: read("Enter the number of columns: "),
NAME%: entermatrix(R%,C%),
L_AAA%,
print(NAME%),
COR%: read("Is this correct (y for Yes, n for No)? "),
if COR%=n then go(START%),
L_A%,
X%: read("Enter either m% or i% or ma% : "),
if X%#m% and X%#i% and X%#ma% then go(L_A%),
L_E1%,
RI%: read("Enter the starting row number: "),
if integerp(RI%)=false or RI%>R% or RI%<1
   then (print("Error!"), go(L_E1%)),
if X%=m% then go(L_B%),
L_E2%,
RF%: read("Enter the ending row number: "),
if integerp(RF%)=false or RF%>R% or RF%<1
   then (print("Error!"), go(L_E2%)),
L_B%,
if X%=m% or X%=ma% then
   (K%: read("Enter the constant which multiplies the starting row: "),
    if X%=m% then print(NAME%:set_element(NAME%,RI%,K%*row(NAME%,RI%)))
    else
    if X%=ma% then print(NAME%:set_element(NAME%,RF%,
                          K%*row(NAME%,RI%)+row(NAME%,RF%)))
   ),
if X%=i% then (CNAME%:copymatrix(NAME%), for i : 1 step 1 thru C% do
	       (CNAME%[RI%,i]:NAME%[RF%,i],CNAME%[RF%,i]:NAME%[RI%,i]),
		NAME%:copymatrix(CNAME%), remvalue(CNAME%), print(NAME%)
	      ),
/* for Macsyma 2.3 or higher one can use instead
   if X%=i% then print(NAME%:swap_rows(NAME%,RI%,RF%)), */
ST%: read("Start with a new matrix (y for Yes, n for No, or e to Exit)? "),
if ST%=y then go(START%) else if ST%=n then go(L_A%) else return(END%(NAME%))
)$
END%(NAME%):=(print("***Program Terminated***"),

              print("Your final matrix, recalled by typing m, is"),
              print(m:NAME%)
)$
save("eros.lsp",GO_EROS,END%)$