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Currency: Difference between revisions
Add Common Lisp version
(→{{header|Rust}}: Correct the formatting of minor currency units (zero-padded) otherwise it prints $2.01 as $2.1) |
imported>GoulashAmateur (Add Common Lisp version) |
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Total with tax: $23683000000000006.16
</pre>
=={{header|Common Lisp}}==
Let us just use the built-in and convenient rationals (which uses two bignums for numerator and denominator).
<syntaxhighlight lang="lisp">(defun print-$ (rat &key (prefix "") (stream t))
(multiple-value-bind (dollars cents) (truncate rat)
(format stream "~A~D.~D~%" prefix dollars (round (* 100 cents)))))
(defun compute-check (order-alist tax-rate)
(let* ((total-before-tax
(loop for (amount . price) in order-alist
sum (* (rationalize price) amount)))
(tax (* (rationalize tax-rate) total-before-tax)))
(print-$ total-before-tax :prefix "Total before tax: ")
(print-$ tax :prefix "Tax: ")
(print-$ (+ total-before-tax tax) :prefix "Total with tax: ")))
(compute-check '((4000000000000000 . 5.5) (2 . 2.86)) 0.0765)</syntaxhighlight>
{{out}}
<pre>Total before tax: 22000000000000005.72
Tax: 1683000000000000.44
Total with tax: 23683000000000006.16</pre>
A reader macro can be used as extra nice icing on the cake:
<syntaxhighlight lang="lisp">(defun read-$ (stream char)
(declare (ignore char))
(let* ((str (with-output-to-string (out)
;; TODO: read integer, if dot, read dot and another integer
(loop :for next = (peek-char nil stream t nil t)
:while (or (digit-char-p next) (char= next #\.))
:do (write-char (read-char stream t nil t) out))))
(dot-pos (position #\. str))
(dollars (parse-integer str :end dot-pos))
(cents (if dot-pos
(/ (parse-integer str :start (+ dot-pos 1))
(expt 10 (- (length str) (+ dot-pos 1))))
0)))
(+ dollars cents)))
(set-macro-character #\$ #'read-$ t)
(defun print-$ (rat &key (prefix "") (stream t))
(multiple-value-bind (dollars cents) (truncate rat)
(format stream "~A~D.~D~%" prefix dollars (round (* 100 cents)))))
(defun compute-check (order-alist tax-rate)
(let* ((total-before-tax
(loop for (amount . price) in order-alist
sum (* price amount)))
(tax (* (rationalize tax-rate) total-before-tax)))
(print-$ total-before-tax :prefix "Total before tax: ")
(print-$ tax :prefix "Tax: ")
(print-$ (+ total-before-tax tax) :prefix "Total with tax: ")))
(compute-check '((4000000000000000 . $5.5) (2 . $2.86)) 0.0765)</syntaxhighlight>
=={{header|Delphi}}==
{{libheader| System.SysUtils}}
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