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# This file provides the runtime support for running a basic program
# Assumes the program has been parsed using basparse.py
import sys
import math
import random
class BasicInterpreter:
# Initialize the interpreter. prog is a dictionary
# containing (line,statement) mappings
def __init__(self, prog):
self.prog = prog
self.functions = { # Built-in function table
'SIN': lambda z: math.sin(self.eval(z)),
'COS': lambda z: math.cos(self.eval(z)),
'TAN': lambda z: math.tan(self.eval(z)),
'ATN': lambda z: math.atan(self.eval(z)),
'EXP': lambda z: math.exp(self.eval(z)),
'ABS': lambda z: abs(self.eval(z)),
'LOG': lambda z: math.log(self.eval(z)),
'SQR': lambda z: math.sqrt(self.eval(z)),
'INT': lambda z: int(self.eval(z)),
'RND': lambda z: random.random()
}
# Collect all data statements
def collect_data(self):
self.data = []
for lineno in self.stat:
if self.prog[lineno][0] == 'DATA':
self.data = self.data + self.prog[lineno][1]
self.dc = 0 # Initialize the data counter
# Check for end statements
def check_end(self):
has_end = 0
for lineno in self.stat:
if self.prog[lineno][0] == 'END' and not has_end:
has_end = lineno
if not has_end:
print("NO END INSTRUCTION")
self.error = 1
return
if has_end != lineno:
print("END IS NOT LAST")
self.error = 1
# Check loops
def check_loops(self):
for pc in range(len(self.stat)):
lineno = self.stat[pc]
if self.prog[lineno][0] == 'FOR':
forinst = self.prog[lineno]
loopvar = forinst[1]
for i in range(pc + 1, len(self.stat)):
if self.prog[self.stat[i]][0] == 'NEXT':
nextvar = self.prog[self.stat[i]][1]
if nextvar != loopvar:
continue
self.loopend[pc] = i
break
else:
print("FOR WITHOUT NEXT AT LINE %s" % self.stat[pc])
self.error = 1
# Evaluate an expression
def eval(self, expr):
etype = expr[0]
if etype == 'NUM':
return expr[1]
elif etype == 'GROUP':
return self.eval(expr[1])
elif etype == 'UNARY':
if expr[1] == '-':
return -self.eval(expr[2])
elif etype == 'BINOP':
if expr[1] == '+':
return self.eval(expr[2]) + self.eval(expr[3])
elif expr[1] == '-':
return self.eval(expr[2]) - self.eval(expr[3])
elif expr[1] == '*':
return self.eval(expr[2]) * self.eval(expr[3])
elif expr[1] == '/':
return float(self.eval(expr[2])) / self.eval(expr[3])
elif expr[1] == '^':
return abs(self.eval(expr[2]))**self.eval(expr[3])
elif etype == 'VAR':
var, dim1, dim2 = expr[1]
if not dim1 and not dim2:
if var in self.vars:
return self.vars[var]
else:
print("UNDEFINED VARIABLE %s AT LINE %s" %
(var, self.stat[self.pc]))
raise RuntimeError
# May be a list lookup or a function evaluation
if dim1 and not dim2:
if var in self.functions:
# A function
return self.functions[var](dim1)
else:
# A list evaluation
if var in self.lists:
dim1val = self.eval(dim1)
if dim1val < 1 or dim1val > len(self.lists[var]):
print("LIST INDEX OUT OF BOUNDS AT LINE %s" %
self.stat[self.pc])
raise RuntimeError
return self.lists[var][dim1val - 1]
if dim1 and dim2:
if var in self.tables:
dim1val = self.eval(dim1)
dim2val = self.eval(dim2)
if dim1val < 1 or dim1val > len(self.tables[var]) or dim2val < 1 or dim2val > len(self.tables[var][0]):
print("TABLE INDEX OUT OUT BOUNDS AT LINE %s" %
self.stat[self.pc])
raise RuntimeError
return self.tables[var][dim1val - 1][dim2val - 1]
print("UNDEFINED VARIABLE %s AT LINE %s" %
(var, self.stat[self.pc]))
raise RuntimeError
# Evaluate a relational expression
def releval(self, expr):
etype = expr[1]
lhs = self.eval(expr[2])
rhs = self.eval(expr[3])
if etype == '<':
if lhs < rhs:
return 1
else:
return 0
elif etype == '<=':
if lhs <= rhs:
return 1
else:
return 0
elif etype == '>':
if lhs > rhs:
return 1
else:
return 0
elif etype == '>=':
if lhs >= rhs:
return 1
else:
return 0
elif etype == '=':
if lhs == rhs:
return 1
else:
return 0
elif etype == '<>':
if lhs != rhs:
return 1
else:
return 0
# Assignment
def assign(self, target, value):
var, dim1, dim2 = target
if not dim1 and not dim2:
self.vars[var] = self.eval(value)
elif dim1 and not dim2:
# List assignment
dim1val = self.eval(dim1)
if not var in self.lists:
self.lists[var] = [0] * 10
if dim1val > len(self.lists[var]):
print ("DIMENSION TOO LARGE AT LINE %s" % self.stat[self.pc])
raise RuntimeError
self.lists[var][dim1val - 1] = self.eval(value)
elif dim1 and dim2:
dim1val = self.eval(dim1)
dim2val = self.eval(dim2)
if not var in self.tables:
temp = [0] * 10
v = []
for i in range(10):
v.append(temp[:])
self.tables[var] = v
# Variable already exists
if dim1val > len(self.tables[var]) or dim2val > len(self.tables[var][0]):
print("DIMENSION TOO LARGE AT LINE %s" % self.stat[self.pc])
raise RuntimeError
self.tables[var][dim1val - 1][dim2val - 1] = self.eval(value)
# Change the current line number
def goto(self, linenum):
if not linenum in self.prog:
print("UNDEFINED LINE NUMBER %d AT LINE %d" %
(linenum, self.stat[self.pc]))
raise RuntimeError
self.pc = self.stat.index(linenum)
# Run it
def run(self):
self.vars = {} # All variables
self.lists = {} # List variables
self.tables = {} # Tables
self.loops = [] # Currently active loops
self.loopend = {} # Mapping saying where loops end
self.gosub = None # Gosub return point (if any)
self.error = 0 # Indicates program error
self.stat = list(self.prog) # Ordered list of all line numbers
self.stat.sort()
self.pc = 0 # Current program counter
# Processing prior to running
self.collect_data() # Collect all of the data statements
self.check_end()
self.check_loops()
if self.error:
raise RuntimeError
while 1:
line = self.stat[self.pc]
instr = self.prog[line]
op = instr[0]
# END and STOP statements
if op == 'END' or op == 'STOP':
break # We're done
# GOTO statement
elif op == 'GOTO':
newline = instr[1]
self.goto(newline)
continue
# PRINT statement
elif op == 'PRINT':
plist = instr[1]
out = ""
for label, val in plist:
if out:
out += ' ' * (15 - (len(out) % 15))
out += label
if val:
if label:
out += " "
eval = self.eval(val)
out += str(eval)
sys.stdout.write(out)
end = instr[2]
if not (end == ',' or end == ';'):
sys.stdout.write("\n")
if end == ',':
sys.stdout.write(" " * (15 - (len(out) % 15)))
if end == ';':
sys.stdout.write(" " * (3 - (len(out) % 3)))
# LET statement
elif op == 'LET':
target = instr[1]
value = instr[2]
self.assign(target, value)
# READ statement
elif op == 'READ':
for target in instr[1]:
if self.dc < len(self.data):
value = ('NUM', self.data[self.dc])
self.assign(target, value)
self.dc += 1
else:
# No more data. Program ends
return
elif op == 'IF':
relop = instr[1]
newline = instr[2]
if (self.releval(relop)):
self.goto(newline)
continue
elif op == 'FOR':
loopvar = instr[1]
initval = instr[2]
finval = instr[3]
stepval = instr[4]
# Check to see if this is a new loop
if not self.loops or self.loops[-1][0] != self.pc:
# Looks like a new loop. Make the initial assignment
newvalue = initval
self.assign((loopvar, None, None), initval)
if not stepval:
stepval = ('NUM', 1)
stepval = self.eval(stepval) # Evaluate step here
self.loops.append((self.pc, stepval))
else:
# It's a repeat of the previous loop
# Update the value of the loop variable according to the
# step
stepval = ('NUM', self.loops[-1][1])
newvalue = (
'BINOP', '+', ('VAR', (loopvar, None, None)), stepval)
if self.loops[-1][1] < 0:
relop = '>='
else:
relop = '<='
if not self.releval(('RELOP', relop, newvalue, finval)):
# Loop is done. Jump to the NEXT
self.pc = self.loopend[self.pc]
self.loops.pop()
else:
self.assign((loopvar, None, None), newvalue)
elif op == 'NEXT':
if not self.loops:
print("NEXT WITHOUT FOR AT LINE %s" % line)
return
nextvar = instr[1]
self.pc = self.loops[-1][0]
loopinst = self.prog[self.stat[self.pc]]
forvar = loopinst[1]
if nextvar != forvar:
print("NEXT DOESN'T MATCH FOR AT LINE %s" % line)
return
continue
elif op == 'GOSUB':
newline = instr[1]
if self.gosub:
print("ALREADY IN A SUBROUTINE AT LINE %s" % line)
return
self.gosub = self.stat[self.pc]
self.goto(newline)
continue
elif op == 'RETURN':
if not self.gosub:
print("RETURN WITHOUT A GOSUB AT LINE %s" % line)
return
self.goto(self.gosub)
self.gosub = None
elif op == 'FUNC':
fname = instr[1]
pname = instr[2]
expr = instr[3]
def eval_func(pvalue, name=pname, self=self, expr=expr):
self.assign((pname, None, None), pvalue)
return self.eval(expr)
self.functions[fname] = eval_func
elif op == 'DIM':
for vname, x, y in instr[1]:
if y == 0:
# Single dimension variable
self.lists[vname] = [0] * x
else:
# Double dimension variable
temp = [0] * y
v = []
for i in range(x):
v.append(temp[:])
self.tables[vname] = v
self.pc += 1
# Utility functions for program listing
def expr_str(self, expr):
etype = expr[0]
if etype == 'NUM':
return str(expr[1])
elif etype == 'GROUP':
return "(%s)" % self.expr_str(expr[1])
elif etype == 'UNARY':
if expr[1] == '-':
return "-" + str(expr[2])
elif etype == 'BINOP':
return "%s %s %s" % (self.expr_str(expr[2]), expr[1], self.expr_str(expr[3]))
elif etype == 'VAR':
return self.var_str(expr[1])
def relexpr_str(self, expr):
return "%s %s %s" % (self.expr_str(expr[2]), expr[1], self.expr_str(expr[3]))
def var_str(self, var):
varname, dim1, dim2 = var
if not dim1 and not dim2:
return varname
if dim1 and not dim2:
return "%s(%s)" % (varname, self.expr_str(dim1))
return "%s(%s,%s)" % (varname, self.expr_str(dim1), self.expr_str(dim2))
# Create a program listing
def list(self):
stat = list(self.prog) # Ordered list of all line numbers
stat.sort()
for line in stat:
instr = self.prog[line]
op = instr[0]
if op in ['END', 'STOP', 'RETURN']:
print("%s %s" % (line, op))
continue
elif op == 'REM':
print("%s %s" % (line, instr[1]))
elif op == 'PRINT':
_out = "%s %s " % (line, op)
first = 1
for p in instr[1]:
if not first:
_out += ", "
if p[0] and p[1]:
_out += '"%s"%s' % (p[0], self.expr_str(p[1]))
elif p[1]:
_out += self.expr_str(p[1])
else:
_out += '"%s"' % (p[0],)
first = 0
if instr[2]:
_out += instr[2]
print(_out)
elif op == 'LET':
print("%s LET %s = %s" %
(line, self.var_str(instr[1]), self.expr_str(instr[2])))
elif op == 'READ':
_out = "%s READ " % line
first = 1
for r in instr[1]:
if not first:
_out += ","
_out += self.var_str(r)
first = 0
print(_out)
elif op == 'IF':
print("%s IF %s THEN %d" %
(line, self.relexpr_str(instr[1]), instr[2]))
elif op == 'GOTO' or op == 'GOSUB':
print("%s %s %s" % (line, op, instr[1]))
elif op == 'FOR':
_out = "%s FOR %s = %s TO %s" % (
line, instr[1], self.expr_str(instr[2]), self.expr_str(instr[3]))
if instr[4]:
_out += " STEP %s" % (self.expr_str(instr[4]))
print(_out)
elif op == 'NEXT':
print("%s NEXT %s" % (line, instr[1]))
elif op == 'FUNC':
print("%s DEF %s(%s) = %s" %
(line, instr[1], instr[2], self.expr_str(instr[3])))
elif op == 'DIM':
_out = "%s DIM " % line
first = 1
for vname, x, y in instr[1]:
if not first:
_out += ","
first = 0
if y == 0:
_out += "%s(%d)" % (vname, x)
else:
_out += "%s(%d,%d)" % (vname, x, y)
print(_out)
elif op == 'DATA':
_out = "%s DATA " % line
first = 1
for v in instr[1]:
if not first:
_out += ","
first = 0
_out += v
print(_out)
# Erase the current program
def new(self):
self.prog = {}
# Insert statements
def add_statements(self, prog):
for line, stat in prog.items():
self.prog[line] = stat
# Delete a statement
def del_line(self, lineno):
try:
del self.prog[lineno]
except KeyError:
pass