# Last modified on Wed Feb  8 14:43:42 PST 1995 by heydon
#
# Add two user-supplied numbers
#
# PROCEDURE r1 := ReadNum() IS <10>
#   t1 :: Print("Enter a number: ")
#       ; t1 := Readln()
#       ; r1 := Atof(t1)
#   END
#   
# PROCEDURE Main() IS <11>
#   r1, r2, t1 :: r1 := ReadNum()
#               ; r2 := ReadNum()
#               ; t1 := FmtReal(Atof(r1 + r2))
#               ; Print("Sum: "); Print(t1); Print("\n")
# END
#
# BEGIN <12>
#   Main()
# END.

V0
"Enter a number: "
V1
"Invalid arguments to ADD"
V2
"Sum: "
V3
"\n"

# PROCEDURE ReadNum
# L[-1] = r1
# L[1] = t1
C1

# INCSP 1 (make space for t1, which is now local variable 1)
.INCSP
b1

# PUSHG 0 "Enter a number:"
.PUSHG
c0

# CALLEXT Print
.CALLEXT
c0

# POPSP 1 (Print IN)
# INCSP 1 (Readln result)

# CALLEXT 1, Readln
.CALLEXT
c1

# POPL t1
.POPL
s1

# INCSP 1 (Atof result)
.INCSP
b1

# PUSHL t1
.PUSHL
s1

# CALLEXT 2, Atof
.CALLEXT
c3

# DECSP 1 (Discard argument)
.DECSP
b1

# POPL r1
.POPL
s-1

# Remove space for temporary
.DECSP
b1

# RET
.RET

# PROCEDURE Main() IS <11>
#   r1, r2, t1 :: r1 := ReadNum()
#               ; r2 := ReadNum()
#               ; t1 := FmtReal(r1 + r2)
#               ; Print(t1)
C2

# INCSP 3 (r1, r2, t1)
.INCSP
b3

# INCSP 1 (out var for Readnum)
.INCSP
b1

# CALL Readnum
.CALL
c1

# POPL r1
.POPL
s1

# INCSP 1 (out var for Readnum #2)
.INCSP
b1

# CALL ReadNum
.CALL
c1

# POPL r2
.POPL
s2

# PUSHL r1
.PUSHL
s1

# PUSHL r2
.PUSHL
s2

# ADD UNDEF
.ADD
s3

# JUMP DEF
.JUMP
s2

# UNDEF: ERROR
.ERROR
b1

# DEF: POPL t1
.POPL
s3

# PUSHG 2 "Sum: "
.PUSHG
c2

# CALLEXT Print
.CALLEXT
c0

# INCSP 1
.INCSP
b1

# PUSHL t1
.PUSHL
s3

# CALLEXT FmtReal
.CALLEXT
c2

# DECSP 1
.DECSP
b1

# CALLEXT Print
.CALLEXT
c0

# PUSHG 3 "\n"
.PUSHG
c3

# CALLEXT Print
.CALLEXT
c0

# RET
.RET

# Change one of the numbers following the END to a non-number to see
# Error Handling
END
1.2
2.3