(1)zoom/enlarge text on firefox-web-browser : press-and-hold control then : press = or press +. (2)shrink text on firefox-web-browser : press-and-hold control then press -. (3)to copy, paste text:find 'problem: copy text' under date '11 nov 2018 10:28 am est' in howto.htm.
math-operator accepted:(1)multiply:x,* (2)plus:+ (3)minus:- (4)parenthesis:() (5)divide:/
max_decimal_digit_repetition_for_division_allowed ( maximum '9', ( integer / non-decimal )-division use '-1' ) : time-stamp on console ?
input:
console/output :

example input:(9x2+1)
/2
28 feb 2019 5:37 pm est>defect:2.9+2.8=5.699999999999999,which should have been 5.7
1 mar 2019 2:29 pm est>i stop working on this calculator-software because
 (1) linuxmint-18.2->cinnamon-gui->gnu-calculator's input can receive copy-paste-multi-line-input
 (2) linuxmint-18.2->cinnamon-gui->gnu-calculator's inputted-math-equation can be clicked then inputted-math-equation can be copy-pasted to other software

11 mar 2019 2:8 pm edt:that defect has been reported to mozilla 20 year ago but never fixed: https://bugzilla.mozilla.org/show_bug.cgi?id=5856#11_mar_2019_2_6_pm_edt from https://bugzilla.mozilla.org/enter_bug.cgi#h=dupes%7CFirefox -> find-similar-issue(addition substraction) result 1
8 apr 2019 10:8 pm edt:finish making calculator from scratch,avoiding that defect,testing...
8 apr 2019 10:13 pm edt:fail for input -6+2/3
10 apr 2019 6:59 pm edt=>7:34 pm edt:succeed for input -6+2/3,can show some calculation-step,add max_decimal_digit_repetition_for_division_allowed textbox
10 apr 2019 8:36 pm edt:making output not showing a repeat
10 apr 2019 8:44 pm edt:fail for input 17/12
10 apr 2019 8:59 pm edt:succeed for input 17/12
10 apr 2019 9:2 pm edt:fail for input 125/12
14 apr 2019 3:55 pm edt:succeed for input 125/12
14 apr 2019 3:59 pm edt:fail for input 733/252
14 apr 2019 4:34 pm edt:succeed for input 733/252, fail for input 2.5 x 2
14 apr 2019 5:25 pm edt:still fail for 733/252,succeed for input 733/252,succeed for input 2.5 x 2
14 apr 2019 5:52 pm edt:fail for input 5 × 5936
16 apr 2019 4:13 pm edt=>4:44 pm edt:succeed for input 5 × 5936
28 apr 2019 9:3 am edt:fail for input 123/1000
28 apr 2019 9:42 am edt:i realise 'fail for input 123/1000' is wrong 123/1000 did not fail,fail for input 12/1000
28 apr 2019 10:9 am edt:succeed for input 12/1000,change division-result-format .5 to 0.5
7 may 2019 5:54 pm edt:fail with input:(1)0.30479999 x 14=04.26719986 (2)1/3.28084=0.333 gnu-calculator: (1)0.30479999 × 14=4.26719986 (2)1/3.28084=0.30479999
7 may 2019 8:44 pm edt:succeed with input (1)0.30479999 x 14=04.26719986 (2)1/3.28084=0.333.now (1)0.30479999 x 14=4.26719986 (2)1/3.28084=0.3047999
7 may 2019 9:9 pm edt:fail with input:1/00.00
7 may 2019 9:14 pm edt:fail with input:1/.00
7 may 2019 9:21 pm edt:succeed with input:1/00.00,1/.00
7 may 2019 9:58 pm edt:fail with input:0/0,then succeed with input:0/0
19 may 2019 4:39 pm edt:fail with input: 127.80+149.98+254.84+327.98+19.99+26.91+113.28+190+327.98+39.95+43.14
19 may 2019 5:9 pm edt:succeed with input: 127.80+149.98+254.84+327.98+19.99+26.91+113.28+190+327.98+39.95+43.14
17 sep 2019 3:42 pm edt:fail 44.93 / 4073
18 sep 2019 3:58 pm edt:succeed 44.93 / 4073, succeed 0.00113 x 407300
18 sep 2019 4:5 pm edt:
gnu-calc vs this-result
17 / 12 = 1.416666667 -> gnu-calc
1.41666 -> this-result
125 / 12 = 10.416666667
10.41666
733 / 252 = 2.908730159
2.9087301587301587301587301587301587301587301587301587301587301587301587301587301587301587301587301587
123 / 1000 = 0.123
0.123
12 / 1000 = 0.012
0.012
1 / 3.28084 = 0.30479999
0.3047999
1 / 00.00 = error : 1/0,can not divide by 0
1 / .00 =error : 1/0, can not divide by 0
0/0 =0
44.93 / 4073 = 0.011031181
0.0110311809477043947949914068254357967100417382764547016940829855143628774858826417873803093542843113

18 sep 2019 4:31 pm edt:fix 'function get_time_stamp()' not showing time-zone-hour-difference-from-utc
18 sep 2019 4:53 pm edt:#add# 44.93 / 4073 =
19 sep 2019 2:23 pm edt:1+1 produce output 1+1=2 only, not:1+1=...[new-line]1+1=2
20 sep 2019 1:34 pm edt:fix failing (-2+1)
20 sep 2019 1:17 pm edt:1+(-2) produce output 1+(-2)=...[new-line]1-2=-1[new-line]1+(-2)=-1
4 apr 2020 3:53 pm edt:fail 6558/11689442
4 apr 2020 5:33 pm edt:6558/11689442 is fixed
13 aug 2020 5:53 pm edt: fail 9223372036854775808 / 2. 9223372036854775808 is [ biggest-number allowed in postgresql ] + 1.
[source: '9223372036854775807' in postgresql.org/docs/9.5/datatype-numeric.html from google ( postgresql database data type ) result 3]
10 nov 2020 1:42 pm est:i delete current-time-stamp-with-time-zone on console-output because current-time-stamp-with-time-zone on console-output is un-necessary-complication during seeing calculation-result.
10 nov 2020 2:47 pm est: succeed 9223372036854775808 / 2 = 4611686018427387904
11 nov 2020 2:19 pm est:fail 300 / 60 = 4.26
11 nov 2020 2:30 pm est:succeed 300 / 60 = 5
;;