Fall $2024$ CIS $524$ Project $($Group Project$)$

$($Due Oct $20)$

In this project you are asked to write an interpreter which uses the top$-$down recursive$-$descent

method to parse and evaluate a very simple programming language. The tiny language's grammar

is given below.

::$=\{\}$

::$=$ let in $()$ end ;

::$=\{\}$

::$=$ id : $=$ ;

::$=$ int $|$ real

::$=\{+|-\}|$

if then else

::$=\{*|/\}$

::$=()|$ id $|$ number $|($ id $)$

::$=<mtext></mtext><mi>|</mi>$

$>|$

$>=|$

$==|$

::$=$ id $|$ intnum

The interpreter $($parser$\_$xxxxxxx$.$py where xxxxxxx is your CSU ID$)$ should be written in Python

with similar structures to the c$++$ version in the Blackboard. It takes one input file $($sample$.$tiny$)$

which is a text file consisting of the statements of the above grammar. The input file name

sample.tiny is given from the command line. The interpreter parser$\_$xxxxxxx$.$py reads the program

file sample.tiny, checks the syntax and outputs the result if the program is legitimate; otherwise,

the interpreter prints "Error".

Below is a test example:

let x : int $=7$ ;

y : real $=3\mathrm{.}0$;

in

real $(($ real $($ x $)+$ y $)*($ real $($ x $)-$ y $))$

end ;

let x $=8$ ; in $($ x $+$ y $)$ end ;

Your program will output

$40\mathrm{.}0$

Error

For another example,

let x : int $=5$ ;

in

int $($ x $+$ x $*$ x $)$

end ;

let r : real $=10\mathrm{.}0$ ;

pi : real $=3\mathrm{.}1416$ ;

in

real $($ pi $*$ r $*$ r $)$

end ;

let a : int $=3$ ;

b : real $=0\mathrm{.}5$ ;

c : real $=$ b $*$ b ;

in

real $($ if a $>5$ then b $+1\mathrm{.}1$ else c $)$

end ;

Your program should display

$30$

$314\mathrm{.}16$

$0\mathrm{.}25$

Submit via Blackboard:

$$ Upload your parser$\_$xxxxxxx$.$py file to the project submission area on Blackboard.

$$ Make sure the file is correctly named using your CSU ID$.$

$$ No other files should be submitted. $```$

let x : int $=5$ ;

in

int $($ x $+$ x $*$ x $)$

end ;

let r : real $=10\mathrm{.}0$ ;

pi : real $=3\mathrm{.}1416$;

in

real $($ pi $*$ r $*$ r $)$

end ;

let a : int $=3$ ;

b : real $=0\mathrm{.}5$ ;

c : real $=$ b $*$ b ;

in

real $($ if a $>5$ then b $+1\mathrm{.}1$ else c $)$

end ;

$```$

Your program should display

$\backslash [$

$\backslash$begin$\{$array$\}\{$l$\}$

$30\backslash \backslash$

$314\mathrm{.}16\backslash \backslash$

$0\mathrm{.}25$

$\backslash$end$\{$array$\}$

$\backslash ]$

Submit via Blackboard:

$-$ Upload your parser$\_$xxxxxxx$.$py file to the project submission area on Blackboard.

$-$ Make sure the file is correctly named using your CSU ID$.$

$-$ No other files should be submitted.