Parsing/RPN calculator algorithm: Difference between revisions
Add CLU
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[24577/8192])
answer: 24577/8192
=={{header|CLU}}==
<lang clu>% Split string by whitespace
split = iter (expr: string) yields (string)
own whitespace: string := " \r\n\t"
cur: array[char] := array[char]$[]
for c: char in string$chars(expr) do
if string$indexc(c, whitespace) = 0 then
array[char]$addh(cur, c)
else
if array[char]$empty(cur) then continue end
yield(string$ac2s(cur))
cur := array[char]$[]
end
end
if ~array[char]$empty(cur) then
yield(string$ac2s(cur))
end
end split
% Tokenize a RPN expression
token = oneof[number: real, op: char]
tokens = iter (expr: string) yields (token) signals (parse_error(string))
own operators: string := "+-*/^"
for t: string in split(expr) do
if string$size(t) = 1 cand string$indexc(t[1], operators)~=0 then
yield(token$make_op(t[1]))
else
yield(token$make_number(real$parse(t)))
except when bad_format:
signal parse_error(t)
end
end
end
end tokens
% Print the stack
print_stack = proc (stack: array[real])
po: stream := stream$primary_output()
for num: real in array[real]$elements(stack) do
stream$puts(po, f_form(num, 5, 5) || " ")
end
stream$putl(po, "")
end print_stack
% Evaluate an expression, printing the stack at each point
evaluate_rpn = proc (expr: string) returns (real) signals (parse_error(string), bounds)
stack: array[real] := array[real]$[]
for t: token in tokens(expr) do
tagcase t
tag number (n: real): array[real]$addh(stack, n)
tag op (f: char):
r: real := array[real]$remh(stack)
l: real := array[real]$remh(stack)
n: real
if f='+' then n := l+r
elseif f='-' then n := l-r
elseif f='*' then n := l*r
elseif f='/' then n := l/r
elseif f='^' then n := l**r
end
array[real]$addh(stack, n)
end
print_stack(stack)
end resignal parse_error
return(array[real]$reml(stack))
end evaluate_rpn
start_up = proc ()
po: stream := stream$primary_output()
expr: string := "3 4 2 * 1 5 - 2 3 ^ ^ / +"
stream$putl(po, "Expression: " || expr)
stream$putl(po, "Result: " || f_form(evaluate_rpn(expr), 5, 5))
end start_up</lang>
{{out}}
<pre>Expression: 3 4 2 * 1 5 - 2 3 ^ ^ / +
3.00000
3.00000 4.00000
3.00000 4.00000 2.00000
3.00000 8.00000
3.00000 8.00000 1.00000
3.00000 8.00000 1.00000 5.00000
3.00000 8.00000 -4.00000
3.00000 8.00000 -4.00000 2.00000
3.00000 8.00000 -4.00000 2.00000 3.00000
3.00000 8.00000 -4.00000 8.00000
3.00000 8.00000 65535.99240
3.00000 0.00012
3.00012
Result: 3.00012</pre>
=={{header|COBOL}}==
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