Toy calculator in Lua, version 1
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function eval(num1, operator, num2) | |
if operator == '+' then | |
return num1 + num2 | |
elseif operator == '-' then | |
return num1 - num2 | |
elseif operator == '*' then | |
return num1 * num2 | |
elseif operator == '/' then | |
return num1 / num2 | |
else | |
return num1 | |
end | |
end | |
spc = lpeg.S(" \t\n")^0 | |
number = spc * lpeg.C( | |
lpeg.P('-')^-1 * | |
lpeg.R('09')^0 * | |
( lpeg.P('.') * | |
lpeg.R('09')^0 | |
)^-1 ) * spc / | |
tonumber | |
expr = lpeg.P{ | |
"EXPR"; | |
EXPR = ( lpeg.V("TERM") * lpeg.C( lpeg.S('+-') ) * lpeg.V("EXPR") + | |
lpeg.V("TERM") ) / eval, | |
TERM = ( lpeg.V("FACT") * lpeg.C( lpeg.S('/*') ) * lpeg.V("TERM") + | |
lpeg.V("FACT") ) / eval, | |
FACT = ( spc * "(" * lpeg.V("EXPR") * ")" * spc + | |
number ) / eval | |
} | |
function repl(file) | |
file = file or io.input() | |
parser = expr | |
for line in file:lines() do | |
print(parser:match(line)) | |
end | |
end |
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