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LuckBasic.tbasic
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LuckBasic.tbasic
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'---script created on 11-08-2022 14:51:59 by
' LuckBasic
' This is my personal project to build a Basic interpreter.
' It's a high level project to prove to myself that i understand how to build an interpreter.
' I'm intentionaly using very simple algorithms and data structures. Readability outweighs performance.
'
' Gary Luckenbaugh - fall of '22
'
uses "console"
uses "file"
dim buff as string
dim buff_after_parse_or as string
dim pc as integer ' Program counter for interpreter
const ops = 10
dim op(ops) as string
dim pTree as Dword
op(1) = "+", "-", "*", "/", "(", ")", "=", "^", "@", ","
buff = ""
' this is a brain dead way to store program lines,
' but without a good collection class I am doing this.
dim statement(5000) as string
dim i as integer
dim at_array(5000) as integer
for i = 1 to 5000
at_array(i) = 2*i ' test pattern
next i
for i = 1 to 5000
statement(i) = ""
next i
function myucase(s as string) as string
dim c(100) as string
dim flag as integer
dim i as integer
dim collect as string
flag = true
collect = ""
for i = 1 to len(s)
c(i) = mid$(s, i, 1)
' console_writeline("character and code = " + c(i) + " code = ", asc(c(i)))
if asc(c(i)) = 0x22 then ' toggle flag
' console_writeline("Toggling flag at "+i)
if flag = true then
flag = false
else
flag = true
end if
end if
if flag = true then
c(i) = Ucase$(c(i))
endif
' console_writeline("character and code = " + c(i) + " code = ", asc(c(i)))
next i
for i = 1 to len(s)
collect = collect + c(i)
next i
myucase = collect
End function
Function tbmain()
dim i as string
dim j as String
dim continue as integer
dim tok as string
start_variable_store()
continue = true
do while continue = true
console_write("Basic> ")
i = console_read()
i = rid_eol(i)
i = myucase(i)
' i = Ucase$(i)
' console_writeline(i)
buff = i
tok = gettok()
if left$(tok, 1) >= "0" and left$(tok, 1) <= "9" then
process_line(i)
elseif tok <> "BYE" then
do_command(i)
elseif tok = "BYE" then
continue = false
end if
loop
Release_variable_store()
TbMain = true
end function
sub edit_delete(linenum as string)
' console_writeline("deleting " + linenum)
statement(val(linenum)) = ""
end sub
sub edit_replace(linenum, buff as string)
' Console_writeline("linenum = "+linenum)
' console_writeline( " buff = "+buff)
statement(val(linenum)) = buff
end sub
sub process_line(i as string)
dim line_tok as string
dim nexttok as string
buff = i
line_tok = gettok()
nexttok = gettok()
if nexttok = "~" then
edit_delete(line_tok)
else
edit_replace(line_tok, nexttok + buff)
end if
end sub
function do_command(cmd as string) as integer
if cmd = "LIST" then
do_list()
elseif left$(cmd, 5) = "PRINT" then
console_writeline(Val(Expr_eval(mid$(cmd, 6))))
buff = buff_after_parse_or ' look for extraneous stuff
if gettok() <> "~" then
console_writeline("warning: extra stuff after expression")
end if
elseif left$(cmd, 3) = "LET" then
do_let(cmd)
buff = buff_after_parse_or ' look for extraneous stuff
if gettok() <> "~" then
console_writeline("warning: extra stuff after expression")
end if
elseif cmd = "NEW"then
do_new()
elseif left$(cmd, 4) = "LOAD" then
do_load(trim$(mid$(cmd, 5)))
Elseif left$(cmd, 4) = "SAVE" then
do_save(trim$(mid$(cmd, 5)))
elseif cmd = "RUN" then
do_run()
else
do_let("LET"+cmd)
buff = buff_after_parse_or ' look for extraneous stuff
if gettok() <> "~" then
console_writeline("warning: extra stuff after expression")
end if
end if
end function
sub do_load(fname as string)
dim sbuffer as string
dim InFileChannel as long
do_new()
InFileChannel = file_open(fname , "INPUT" )
' console_writeline(InFileChannel)
if InfileChannel = 0 then
console_writeline(fname + " not found")
exit sub
end if
do while not file_eof(InFileChannel)
sBuffer = file_lineinput(InFileChannel)
process_line(sbuffer)
loop
file_close(InFileChannel)
end sub
sub do_save(fname as string)
dim OutFileChannel as long
OutFileChannel = file_open(fname, "OUTPUT")
if OutFileChannel = 0 then
console_writeline(fname + " not writeable")
exit sub
end if
for i = 1 to 5000
if statement(i) <> "" then
File_lineprint(OutFileChannel, Format$(i) + " " + statement(i))
end if
next i
file_close(OutFileChannel)
end sub
sub do_new()
for i = 1 to 5000
statement(i) = ""
next i
end sub
Sub do_list()
for i = 1 to 5000
if statement(i) <> "" then
console_writeline(format$(i) + " " +statement(i))
end if
next i
End Sub
' UDTs don't seem to be working, so I'm doing this instead
' This the FOR-NEXT stack
dim acvar(100) as string
dim aistart(100) as integer
dim ailast(100) as integer
dim aistep(100) as integer
dim ailine(100) as integer
dim for_stackp as integer
dim gosub_stack(100) as integer
dim gosub_stack_ptr as integer
sub do_run()
dim startpc as integer
dim stoprun as integer
dim cmd as string
dim target as integer
startpc = 0
for_stackp = 0
gosub_stack_ptr = 0
stoprun = false
for pc = 1 to 5000
if statement(pc) <> "" then
startpc = pc
exit for
end if
next pc
if startpc = 0 then
Console_writeline("No statements in buffer!")
exit sub
end if
'statement(5000) = "END"
pc = startpc
do while not stoprun and pc <> 0
cmd = statement(pc)
if left$(cmd, 3) = "LET" then
do_let(cmd)
buff = buff_after_parse_or ' look for extraneous stuff
if gettok() <> "~" then
console_writeline("warning: extra stuff after LET expression on line " +pc)
end if
elseif left$(cmd, 5) = "PRINT" then
do_print(cmd)
elseif left$(cmd, 4) = "GOTO" then
pc = do_goto(cmd) - 1
elseif left$(cmd, 5) = "GOSUB" then
pc = do_gosub(cmd) -1
elseif left$(cmd, 7) = "RETURN" then
pc = do_return()
elseif cmd = "END" or cmd = "STOP" then
stoprun = true
elseif left$(cmd, 2) = "IF" then
target = do_if(cmd)
if target <> 0 then
pc = target - 1
end if
elseif left$(cmd, 5) = "INPUT" then
do_input(cmd)
Elseif left$(cmd, 3) = "FOR" then
do_for(cmd)
elseif left$(cmd, 4) = "NEXT" then
do_next(cmd)
else
cmd = "LET" + cmd
do_let(cmd)
' console_writeline("Don't know " + cmd)
end if
if left$(cmd, 4) <> "NEXT" then
pc = next_pc(pc)
end if
' console_writeline("Next PC is "+pc)
loop
end sub
sub do_print(cmd as string)
dim tok as string
dim comma_last as integer
comma_last = false
buff = mid$(cmd, 6)
tok = gettok()
if tok = "~" then
console_writeline("")
Exit sub
end if
do while tok<> "~"
comma_last = false
if lefT$(tok, 1) = chr$(0x22) then
tok = mid$(tok, 2, len(tok) - 2)
console_write(tok + " ")
tok = gettok()
if tok = "," then
tok = gettok()
comma_last = true
end if
else
console_write(Expr_eval(tok + buff) + " ")
buff = buff_after_parse_or
tok = gettok()
if tok = "," then
tok = gettok()
comma_last = true
endif
end if
loop
if not comma_last then
console_writeline("")
end if
end sub
function do_if(cmd as string) as integer
Dim b as integer
dim linenum as integer
b = val(Expr_eval(mid$(cmd, 3)))
buff = buff_after_parse_or ' look for extraneous stuff
if gettok() <> "THEN" then
console_writeline("warning: THEN not found right after expression end on line " + pc)
end if
i = instr(1, cmd, "THEN")
if i <> 0 then
linenum = val(mid$(cmd, i + 4))
' console_writeline("if target is " + linenum)
else
console_writeline("malformed command is :" + cmd + ": missing THEN")
linenum = 0
end if
if b then
do_if = linenum
else
do_if = 0
end if
end function
sub do_for(cmd as string)
cmd = mid$(cmd, 4)
buff = cmd
dim cvar as string
dim tok as string
cvar = gettok()
if gettok() <> "=" then
console_writeline("Missing = in FOR statment on line "+pc)
exit sub
endif
dim istart as integer
dim ilast as integer
dim istep as integer
istart = Val(Expr_eval(buff))
buff = buff_after_parse_or
if gettok() <> "TO" then
Console_writeline("Missing TO in FOR on line "+pc)
exit sub
end if
ilast = Val(Expr_eval(buff))
buff = buff_after_parse_or
istep = 1
if gettok() = "STEP" then
istep = VAL(Expr_eval(buff))
end if
buff = buff_after_parse_or
if gettok() <> "~" then
console_writeline("Extraneous stuff after STEP value on line " +pc)
endif
' console_writeline("var = "+cvar)
' Console_writeline("start is " + istart)
' Console_writeline("last is " + ilast)
' Console_writeline("step = "+ istep)
for_stackp = for_stackp + 1
acvar(for_stackp) = cvar
aistart(for_stackp) = istart
ailast(for_stackp) = ilast
aistep(for_stackp) = istep
ailine(for_stackp) = pc
Set_variable(cvar, format$(istart))
' console_writeline("FOR " + cvar + " for_stackp = "+ for_stackp)
end sub
sub do_next(cmd as string)
' console_writeline(cmd)
' console_writeline("NEXT " + " for_stackp " + for_stackp)
if for_stackp >= 1 then
' console_writeline("NEXT "+acvar(for_stackp))
' console_writeline(aistart(for_stackp))
' console_writeline(ailast(for_stackp))
' console_writeline(aistep(for_stackp))
' console_writeline(ailine(for_stackp))
else
console_writeline("stack underflow NEXT without FOR on line "+pc)
pc = next_pc(pc)
exit sub
end if
cmd = mid$(cmd, 5)
buff = cmd
dim controlvariable as string
controlvariable = gettok()
' console_writeline("control variable for NEXT is "+ controlvariable)
' console_writeline("control variable on stack is "+acvar(for_stackp))
if controlvariable <> acvar(for_stackp) then
console_writeline("mismatched next on line "+pc)
endif
dim var as string
dim start as integer
dim last as integer
dim istep as integer
dim iline as integer
start = aistart(for_stackp)
last = ailast(for_stackp)
istep = aistep(for_stackp)
iline = ailine(for_stackp)
var = acvar(for_stackp)
dim v as integer
v = val(Get_variable(var))
v = v + istep
if istep >= 0 then
if v > last then
' console_writeline("popping "+ "var = "+var)
pc = next_pc(pc)
for_stackp = for_stackp - 1
if for_stackp > 0 then
' console_writeline(" pc is now "+pc)
' console_writeline(" for_stackp is "+for_stackp)
' console_writeline(" control variable will now be "+ acvar(for_stackp))
else
' console_writeline("End of loops")
endif
else
pc = next_pc(iline)
end if
else
if v < last then
pc = next_pc(pc)
else
pc = next_pc(iline)
end if
end if
Set_variable(var, format$(v))
end sub
function next_pc(pc as integer) as integer
' console_writeline("look for next statment after "+pc)
for i = pc + 1 to 5000
if statement(i) <> "" then
next_pc = i
exit function
end if
next i
next_pc = 0
end Function
function do_goto(cmd as string) as integer
do_goto = val(mid$(cmd, 5))
end function
function do_gosub(cmd as string) as integer
do_gosub = val(mid$(cmd, 6))
gosub_stack_ptr = gosub_stack_ptr + 1
gosub_stack(gosub_stack_ptr)= pc
end function
function do_return() as integer
do_return = gosub_stack(gosub_stack_ptr)
gosub_stack_ptr = gosub_stack_ptr - 1
end function
sub do_let(cmd as string)
dim var as string
dim firstchar as string
' console_writeline("cmd = "+cmd)
buff = mid$(cmd, 4)
var = gettok()
' console_writeline("buff = '" + buff+ "' " + "var ="+var)
if var = "@" then
do_let_at_array(buff)
exit sub
end if
firstchar = left$(var, 1)
if not (firstchar >= "A" and firstchar <= "Z") then
console_writeline("Variable name must follow LET")
exit sub
elseif gettok() <> "=" then
Console_writeline("Missing '=' in LET " + cmd)
exit sub
end if
Set_variable(var, Expr_eval(buff))
end sub
sub do_let_at_array(e as string)
' There be lots of demons here that usually happen in C, but not Basic.
' I am going to disallow the use of the logical = symbol on the left side of
' a LET command. This will disallow statements like LET @((1=2)+10) = 3. The first
' equal sign is for logical equivalence where the second is for assignment.
' dim i as integer
dim leftstr as string
dim rightstr as string
dim leftval as integer
dim rightval as integer
dim rpn as string
' console_writeline("e is "+e)
' i = instr(1, e, "=")
' console_writeline("i is "+i)
' if i = 0 then
' console_writeline("No assignment operator in let for @ array")
' exit sub
' end if
' leftstr = mid$(e, 1, i-1)
' rightstr = mid$(e, i+1)
' console_writeline("left str is "+leftstr)
' console_writeline("right str is "+rightstr)
' leftval = val(Expr_eval(leftstr))
' console_writeline("leftstr is "+leftstr+"leftval is "+leftval)
' rightval = val(Expr_eval(rightstr))
' console_writeline("left is "+leftval+" and right is "+rightval)
buff = e
if gettok() <> "(" then
console_writeline("an open left paren ( must follow @ in let")
exit sub
endif
rpn = parse_or()
if gettok() <> ")" then
console_writeline("missing right paren ) in LET @")
exit sub
end if
buff_after_parse_or = buff
leftval = val(Eval_rpn(rpn))
buff = buff_after_parse_or
If gettok() <> "=" then
Console_writeline("missing = in LET @")
exit sub
end if
rightval = Val(Eval_rpn(parse_or()))
' console_writeline("leftval = "+leftval)
if not (leftval >= 1 and leftval <= 5000) then
console_writeline("subscript out of bounds on left side of assignment is "+leftval)
exit sub
end if
at_array(leftval) = Format$(rightval)
end sub
sub do_input(cmd as string)
dim var as string
dim firstchar as string
' console_writeline("cmd = "+cmd)
buff = mid$(cmd, 6)
var = gettok()
' console_writeline("buff = '" + buff+ "' " + "var ="+var)
if var = "@" then
do_input_at_array(buff)
exit sub
end if
firstchar = left$(var, 1)
if not (firstchar >= "A" and firstchar <= "Z") then
console_writeline("Variable name must follow INPUT")
exit sub
end if
dim user_input as string
user_input = console_read()
var = Trim$(Remove$(var, $CRLF))
Set_variable(var, Expr_eval(user_input))
end sub
sub do_input_at_array(e as string)
' There be lots of demons here that usually happen in C, but not Basic.
' I am going to disallow the use of the logical = symbol on the left side of
' a LET command. This will disallow statements like LET @((1=2)+10) = 3. The first
' equal sign is for logical equivalence where the second is for assignment.
' dim i as integer
dim user_input as string
dim subval as integer
dim inpval as integer
dim rpn as string
buff = e
if gettok() <> "(" then
console_writeline("an open left paren ( must follow @ in INPUT")
exit sub
endif
rpn = parse_or()
if gettok() <> ")" then
console_writeline("missing right paren ) in INPUT @")
exit sub
end if
subval = val(Eval_rpn(rpn))
user_input = console_read()
inpval = Val(Expr_eval(user_input))
if not (subval >= 1 and subval <= 5000) then
console_writeline("subscript out of bounds on left side of INPUT @ is " + subval)
exit sub
end if
at_array(subval) = Format$(inpval)
end sub
Function Eval_rpn(rpn as string) as string
buff = rpn
dim tok as string
clearstack()
tok = gettok()
if tok = "~" then
Eval_rpn = "0"
exit function
end if
do while tok<> "~"
' console_writeline("Doing tok "+tok)
process_tok(tok)
tok = gettok()
loop
dim r as string
r = mypop()
' console_writeline("result is "+r)
Eval_rpn = format$(r)
End Function
function Expr_eval(e as string) as string
clearstack()
buff = e
buff = parse_or()
' console_writeline("RPN = " + buff + " after parse_or")
dim tok as string
tok = gettok()
if tok = "~" then
Expr_eval = "0"
exit function
end if
do while tok<> "~"
' console_writeline("Doing tok "+tok)
process_tok(tok)
tok = gettok()
loop
dim r as integer
r = mypop()
' console_writeline("result is "+r)
Expr_eval = format$(r)
End function
sub process_tok(tok as string)
dim i as integer
if tok = "UNM" then
mypush(Format$(-val(mypop())))
exit sub
end if
if tok = "GETAT" then
' mypush(Format$(val(at_array(mypop()))))
i = mypop()
if i < 1 or i > 5000 then
console_writeline("Subscript out of range 1..5000 for " + i)
mypush(format$(0))
Exit Sub
end if
mypush(format$(at_array(i)))
exit sub
end if
for i = 1 to ops
if op(i) = tok then
process_op(op(i))
exit sub
end if
next i
dim logical_op(7) as string
logical_op(1) = "<", "<=", "=", ">", ">=", "AND", "OR"
for i = 1 to 7
if logical_op(i) = tok then
' Console_writeline("logical op " + logical_op(i))
process_op(logical_op(i))
exit sub
end if
next i
process_num_or_var(tok)
end sub
sub process_op(op as string)
dim leftval as integer
Dim rightval as integer
dim res as integer
rightval = Val(mypop())
leftval = Val(mypop())
If op = "+" then
res = leftval + rightval
elseif op = "-" then
res = leftval - rightval
elseif op = "*" then
res = leftval*rightval
elseif op = "/" then
res = leftval/rightval
elseif op = "^" then
res = leftval ^ rightval
elseif op = "<" then
res = leftval < rightval
elseif op = "<=" then
res = leftval <= rightval
elseif op = "=" then
' console_writeline("= "+leftval+" "+rightval)
res = leftval = rightval
elseif op = ">" then
res = leftval > rightval
elseif op = ">=" then
res = leftval >= rightval
elseif op = "AND" then
' console_writeline("and "+leftval+" "+rightval)
res = leftval and rightval
elseif op = "OR" then
res = leftval or rightval
else
Console_writeline("Not an operator")
exit sub
End if
mypush(format$(res))
end sub
sub process_num_or_var(num as string)
if left$(num, 1) >= "0" and left$(num,1) <= "9" then
mypush(num)
else
mypush(Get_variable(num))
end if
end sub
dim mystack(50) as string
dim sp as integer
Sub clearstack()
sp = 1
end sub
Sub mypush(tok as string)
' console_writeline("push " + tok)
mystack(sp) = tok
sp = sp + 1
end sub
Function mypop() as string
sp = sp - 1
' console_writeline("pop sp = "+sp + "tok = " + mystack(sp))
mypop = mystack(sp)
end function
' There must be an API for this, but for now this will work
' Found the API, but my function calls the API
Function rid_eol(inp as string) as string
' rid_eol = mid$(inp, 1, len(inp)-2)
rid_eol = Remove$(inp, $CRLF)
end function
function Start_variable_store()
pTree = Tree_New
End Function
Function Set_variable(key as string, item as string)
Tree_Set(pTree, key, item)
End Function
Function Get_variable(key as string) as string
Get_variable = Tree_Get(pTree, key)
end function
function Release_variable_store()
Tree_Free(pTree)