Difference between revisions of "Calc"

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[http://www.emacswiki.org/emacs/CategoryCalculators Category Calculators -Emacs Wiki-]
 
[http://www.emacswiki.org/emacs/CategoryCalculators Category Calculators -Emacs Wiki-]
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== from emacs lisp via calc-eval ==
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Calc may be invoked from [[Emacs_Lisp]] via [https://www.gnu.org/software/emacs/manual/html_node/calc/Calling-Calc-from-Your-Programs.html#Calling-Calc-from-Your-Programs calc-eval]. Try these examples in a ''*scratch*'' or [[IELM]] buffer, or via a shell one-liner in [https://www.gnu.org/software/emacs/manual/html_node/emacs/Initial-Options.html#Initial-Options batch mode].
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=== using calc-eval ===
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''calc-eval'' accepts a string containing an [https://www.gnu.org/software/emacs/manual/html_node/calc/Algebraic-Entry.html#Algebraic-Entry algebraic expression] as its first argument, and returns the result of evaluating the expression in a string.
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<source lang=lisp>
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;; emacs lisp
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(calc-eval "sqrt(2 ^ 16)"))
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;; ==> "256"
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</source>
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<source lang=bash>
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# shell
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emacs -Q -batch --eval='(message "%s" (calc-eval "sqrt(2 ^ 16)"))'
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# ==> 256
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</source>
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=== floating point numbers ===
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[https://www.gnu.org/software/emacs/manual/html_node/calc/Floats.html#Floats Floats] default to 12 digits of [https://www.gnu.org/software/emacs/manual/html_node/calc/Precision.html#Precision precision], with the final digit rounded.
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<source lang=lisp>
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;; emacs lisp
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(calc-eval (calc-eval "2 / 3")
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;; ==> "0.666666666667"
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</source>
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<source lang=bash>
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# shell
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emacs -Q -batch --eval='(message "%s" (calc-eval "2 / 3"))'
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# ==> 0.666666666667
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</source>
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'''Note:''' The shell examples use ''message'' to cause the evaluation result to be printed. In emacs lisp, printing is a [https://en.wikipedia.org/wiki/Side_effect_%28computer_science%29 side effect] which only occurs when you ask for it. ''IELM'' displays the result as a convenience, and ''*scratch*'' only inserts then result depending on how you invoke it (such as with [https://www.gnu.org/software/emacs/manual/html_node/emacs/Lisp-Interaction.html#Lisp-Interaction eval-print-last-sexp]). ''message'' doesn't preserve quotation marks around strings because its output is intended for humans, not the lisp reader. In ''-batch'' mode, ''message'' prints to standard error, but ''print'' could be used to direct results to standard output.
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=== lists ===
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If the string is a comma-delimited list of expressions, then a comma-delimited list of results will be returned.
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<source lang=lisp>
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;; emacs lisp
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(calc-eval "9 / 5, trunc(9 / 5), 9 % 5")
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;; ==> "1.8, 1, 4"
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</source>
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<source lang=bash>
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# shell
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emacs -Q -batch --eval='(message "%s" (calc-eval "9 / 5, trunc(9 / 5), 9 % 5"))'
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# ==> 1.8, 1, 4
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</source>
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=== random numbers ===
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[https://www.gnu.org/software/emacs/manual/html_node/calc/Random-Numbers.html#Random-Numbers Calc's random number generator] is seeded from the system time when calc is started. ''random(N)'' returns a non-negative integer less than ''N''. Your results should vary from the examples below.
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<source lang=lisp>
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;; emacs lisp
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(calc-eval "1 + random(6), 1 + random(6), 1 + random(6)")
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;; ==> "1, 4, 3"
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</source>
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<source lang=bash>
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# shell
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emacs -Q -batch --eval='(message "%s" (calc-eval "1 + random(6), 1 + random(6)"))'
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# ==> 5, 2
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</source>
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=== fractions ===
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[https://www.gnu.org/software/emacs/manual/html_node/calc/Fractions.html#Fractions Fractions] are written as ''NUMERATOR:DENOMINATOR'' to distinguish them from divison operations. Mixed fractions may be entered as ''WHOLE:NUMERATOR:DENOMINATOR''. Fraction results are reduced to lowest terms, and may be improper fractions.
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<source lang=lisp>
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;; emacs lisp
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(calc-eval "2:1:4 + 1:2")
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;; ==> "11:4"
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</source>
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<source lang=bash>
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# shell
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emacs -Q -batch --eval='(message "%s" (calc-eval "2:1:4 + 1:2"))'
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# ==> 11:4
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</source>
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=== entering non-decimal integers ===
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[https://www.gnu.org/software/emacs/manual/html_node/calc/Integers.html#Integers integers] may be entered as ''RADIX#VALUE'', where ''RADIX'' may range from 2 to 36 inclusive.
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'''Caution!''' This is '''not''' the same [https://www.gnu.org/software/emacs/manual/html_node/elisp/Integer-Basics.html#Integer-Basics notation used by emacs lisp].
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<source lang=lisp>
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;; emacs lisp
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(calc-eval "2#10 * 8#10")
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;; ==> "16"
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</source>
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<source lang=bash>
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# shell
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emacs -Q -batch --eval='(message "%s" (calc-eval "2#10 * 8#10"))'
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# ==> 16
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</source>
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== advanced calc-eval ==
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If the first argument to ''calc-eval'' is a list, then the first element of the list should be an algebraic expression in a string. Remaining elements of the list are zero or more ''NAME VALUE'' pairs which specify [https://www.gnu.org/software/emacs/manual/html_node/calc/Mode-Settings.html#Mode-Settings mode settings].
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'''Important:''' In emacs lisp <nowiki>'(foo)</nowiki> is a [https://www.gnu.org/software/emacs/manual/html_node/elisp/Quoting.html#Quoting quoted] list, but <nowiki>'</nowiki> (apostrophe) is special to the shell. Lisp expressions in previous shell examples were wrapped in <nowiki>'</nowiki> (apostrophe) symbols to prevent the shell from interpreting them. In the following shell examples, ''(quote (foo bar))'' makes a quoted list without breaking the [https://www.gnu.org/software/bash/manual/html_node/Quoting.html#Quoting shell quoting].
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=== non-decimal integer results ===
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<source lang=lisp>
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;; emacs lisp
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(calc-eval '("2 * 8" calc-number-radix 16))
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;;  ==> "16#10"
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</source>
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<source lang=bash>
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# shell
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emacs -Q -batch --eval='(message "%s" (calc-eval (quote ("20" calc-number-radix 16))))'
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# ==> 16#14
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</source>
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=== setting numeric precision ===
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<source lang=lisp>
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;; emacs lisp
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(calc-eval '("2 / 3" calc-internal-prec 20))
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;; ==> "0.66666666666666666667"
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</source>
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<source lang=bash>
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# shell
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emacs -Q -batch --eval='(message "%s" (calc-eval (quote ("2 / 3" calc-internal-prec 20))))'
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# ==> 0.66666666666666666667
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</source>
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=== setting angular mode ===
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<source lang=lisp>
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;; emacs lisp
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(calc-eval '("arctan2(0, -1)" calc-internal-prec 20 calc-angle-mode rad))
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;; ==> "3.1415926535897932385"
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</source>
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<source lang=bash>
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# shell
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emacs -Q -batch --eval='(message "%s" (calc-eval (quote ("arctan2(0, -1)" calc-angle-mode rad))))'
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# ==> 3.14159265359
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</source>

Latest revision as of 01:57, 22 February 2016

Calc comes with GNU Emacs starting with version 22.

The GNU Emacs Calculator

Category Calculators -Emacs Wiki-

from emacs lisp via calc-eval

Calc may be invoked from Emacs_Lisp via calc-eval. Try these examples in a *scratch* or IELM buffer, or via a shell one-liner in batch mode.

using calc-eval

calc-eval accepts a string containing an algebraic expression as its first argument, and returns the result of evaluating the expression in a string. 

;; emacs lisp
(calc-eval "sqrt(2 ^ 16)"))
;; ==> "256"

# shell
emacs -Q -batch --eval='(message "%s" (calc-eval "sqrt(2 ^ 16)"))'
# ==> 256

floating point numbers

Floats default to 12 digits of precision, with the final digit rounded. 

;; emacs lisp
(calc-eval (calc-eval "2 / 3")
;; ==> "0.666666666667"

# shell
emacs -Q -batch --eval='(message "%s" (calc-eval "2 / 3"))'
# ==> 0.666666666667

Note: The shell examples use message to cause the evaluation result to be printed. In emacs lisp, printing is a side effect which only occurs when you ask for it. IELM displays the result as a convenience, and *scratch* only inserts then result depending on how you invoke it (such as with eval-print-last-sexp). message doesn't preserve quotation marks around strings because its output is intended for humans, not the lisp reader. In -batch mode, message prints to standard error, but print could be used to direct results to standard output.

lists

If the string is a comma-delimited list of expressions, then a comma-delimited list of results will be returned. 

;; emacs lisp
(calc-eval "9 / 5, trunc(9 / 5), 9 % 5")
;; ==> "1.8, 1, 4"

# shell
emacs -Q -batch --eval='(message "%s" (calc-eval "9 / 5, trunc(9 / 5), 9 % 5"))'
# ==> 1.8, 1, 4

random numbers

Calc's random number generator is seeded from the system time when calc is started. random(N) returns a non-negative integer less than N. Your results should vary from the examples below. 

;; emacs lisp
(calc-eval "1 + random(6), 1 + random(6), 1 + random(6)")
;; ==> "1, 4, 3"

# shell
emacs -Q -batch --eval='(message "%s" (calc-eval "1 + random(6), 1 + random(6)"))'
# ==> 5, 2

fractions

Fractions are written as NUMERATOR:DENOMINATOR to distinguish them from divison operations. Mixed fractions may be entered as WHOLE:NUMERATOR:DENOMINATOR. Fraction results are reduced to lowest terms, and may be improper fractions. 

;; emacs lisp
(calc-eval "2:1:4 + 1:2")
;; ==> "11:4"

# shell
emacs -Q -batch --eval='(message "%s" (calc-eval "2:1:4 + 1:2"))'
# ==> 11:4

entering non-decimal integers

integers may be entered as RADIX#VALUE, where RADIX may range from 2 to 36 inclusive.

Caution! This is not the same notation used by emacs lisp. 

;; emacs lisp
(calc-eval "2#10 * 8#10")
;; ==> "16"

# shell
emacs -Q -batch --eval='(message "%s" (calc-eval "2#10 * 8#10"))'
# ==> 16

advanced calc-eval

If the first argument to calc-eval is a list, then the first element of the list should be an algebraic expression in a string. Remaining elements of the list are zero or more NAME VALUE pairs which specify mode settings.

Important: In emacs lisp '(foo) is a quoted list, but ' (apostrophe) is special to the shell. Lisp expressions in previous shell examples were wrapped in ' (apostrophe) symbols to prevent the shell from interpreting them. In the following shell examples, (quote (foo bar)) makes a quoted list without breaking the shell quoting.

non-decimal integer results

;; emacs lisp
(calc-eval '("2 * 8" calc-number-radix 16))
;;  ==> "16#10"

# shell
emacs -Q -batch --eval='(message "%s" (calc-eval (quote ("20" calc-number-radix 16))))'
# ==> 16#14

setting numeric precision

;; emacs lisp
(calc-eval '("2 / 3" calc-internal-prec 20))
;; ==> "0.66666666666666666667"

# shell
emacs -Q -batch --eval='(message "%s" (calc-eval (quote ("2 / 3" calc-internal-prec 20))))'
# ==> 0.66666666666666666667

setting angular mode

;; emacs lisp
(calc-eval '("arctan2(0, -1)" calc-internal-prec 20 calc-angle-mode rad))
;; ==> "3.1415926535897932385"

# shell
emacs -Q -batch --eval='(message "%s" (calc-eval (quote ("arctan2(0, -1)" calc-angle-mode rad))))'
# ==> 3.14159265359
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