L$4-$template.py:

# Turn diagnostics on$/$off by setting VERBOSE True$/$False$.$

VERBOSE $=$ True

def L$4($inString$)$:

# inString is a white$-$space delimited list of string representations

# of decimal ints. For example, $\text{'}7-65-28\text{'}$ is a valid inString.

#

# For lab #$4,$ add code to L$4()$ that parses inString and computes the

# count of positive ints equal to $2$ mod $3,$ as well as storing the

# last negative int.

#

# If inString contains a white$-$space delimited substring of symbols that

# is not a valid decimal int, L$4($inString$)$ returns $\text{'}$no$\text{'}$;

# else if inString does not contain any negative ints, L$4($inString$)$

# returns $\text{'}$no$\text{'}$;

# else if the count of positive ints equal to $2$ mod $3$ does not match

# the absolute value of the last negative int, L$4($inString$)$ returns $\text{'}$no$\text{'}$;

# else L$4($inString$)$ returns 'yes'.

#

# For example, if inString $=\text{'}7-65-28\text{'},$ L$4($inString$)$ would

# return 'yes' because inString contains two positive ints equal to $2$

# mod $3(5$ and $8),$ and the absolute value of the last negative int

# in inString is $2$; if inString $=\text{'}-11-23-58\text{'},$ L$4($inString$)$

# returns $\text{'}$no$\text{'}$ because there is only one positive int equal to $2$ mod $3,$

# not $5$; if inString $=\text{'}112358\text{'},$ L$4($inString$)$ returns $\text{'}$no$\text{'}$

# because inString does not contain any negative int; and if inString $=$

# $\text{'}7-65-2$ x$0$F $8\text{'},$ L$4($inString$)$ returns $\text{'}$no$\text{'}$ because $\text{'}$x$0$F$\text{'}$ is not

# a valid representation of a decimal int.

#

# Do not insert any print statements into this function. If you want to

# show the result, print the return value.

return 'yes'

if $\_\_$name$\_\_==\text{'}\_\_$main$\_\_\text{'}$:

def test$\_$case$($F$,$string,expected,num,comment$=\text{'}\text{'})$:

err $=\text{'}**\text{'}$

result $=$ F$($string$)$

func$\_$name $=$ str$($F$).$split$()[1]$

func$\_$call $=$ f$\text{'}\text{'}\text{'}\{$func$\_$name$\}("\{$string$\}")\text{'}\text{'}\text{'}$

if result $==$ expected: err $=\text{'}\text{'}$

e $=$ expected

print $($f$\text{'}\{$err$\}$test #$\{$num$\}\{$func$\_$call$\}$: expected $"\{$e$\}",$ received

$"\{$result$\}"\text{'})$

print $($f$\text{'}$test #$\{$num$\}$ Explanation: $\{$comment$\}$

$\text{'})$

return num $+1$

num $=1$

s $=\text{'}7-65-28\text{'}$

exp $=\text{'}2$ positive ints $=23,-2$ is the last negative int'

num $=$ test$\_$case$($L$4,$s$,$'yes',num,exp$)$

s $=\text{'}-11-23-58\text{'}$

exp $=$ 'Only one positive int equal to $2$ mod $3,$ not $5\text{'}$

num $=$ test$\_$case$($L$4,$s$,\text{'}$no$\text{'},$num,exp$)$

s $=\text{'}112358\text{'}$

exp $=\text{'}$no negative ints'

num $=$ test$\_$case$($L$4,$s$,\text{'}$no$\text{'},$num,exp$)$

s $=\text{'}7-65-2$ x$0$F $8\text{'}$

exp $=\text{'}$x$0$F is not a valid representation of a decimal int'

num $=$ test$\_$case$($L$4,$s$,\text{'}$no$\text{'},$num,exp$)$

Modify the attached program L$4-$template.py to create a SISO $($String In$,$ String Out$)$ Python decision function with the following properties:

$$ The expected input parameter inString is a string encoding integers delimited by white space. For example, $\text{'}7-65-28\text{'}$ is a valid inString.

$$ The function L$4()$ should parse inString and compute the count of positive ints equal to $2$ mod $3,$ as well as storing the last negative int. Note that the Python mod operator is $\text{'}\%\text{'},$and thus these expressions all evaluate to True: $7\%3==1$; $5\%3==8\%3==2.$

$$ If inString contains a white$-$space delimited substring of symbols that is not a valid decimal int, L$4($inString$)$ returns $\text{'}$no$\text{'}$;

else if inString does not contain any negative ints, L$4($inString$)$ returns $\text{'}$no$\text{'}$;

else if the count of positive ints equal to $2$ mod $3$ does not match the absolute value of the last negative int, L$4($inString$)$ returns $\text{'}$no$\text{'}$;

else L$4($inString$)$ returns 'yes'.

L$4.$py comes with a test harness initialized with $4$ test cases. Executing L$4$ prints a hand$-$coded explanation for the expected results, and flags unexpected results with $\text{'}**\text{'}.$ The template just returns 'yes' for all inputs, resulting in this output:

test #$1$ L$4("7-65-28")$: expected "yes", received "yes"

test #$1$ Explanation: $2$ positive ints $=23,-2$ is the last negative int

$**$ test #$2$ L$4("-11-23-58")$: expected $"$no$",$ received "yes"

test #$2$ Explanation: Only one positive int equal to $2$ mod $3,$ not $5$

$**$ test #$3$ L$4("112358")$: expected $"$no$",$ received "yes"

test #$3$ Explanation: no negative ints

$**$ test #$4$ L$4("7-65-2$ x$0$F $8")$: expected $"$no$",$ received "yes"

test #$4$ Explanation: x$0$F is not a valid representation of a decimal int

A correct implementation would return $\text{'}$no$\text{'}$ for test cases $2,3,$ and $4,$ while still returning 'yes' for test case $1.$